Title Page
 Table of Contents
 Photodocumentation: The uses, the...
 Case study: Maitland Art Cente...
 Analysis of the case study
 Appendix A: Rectified photography...
 Appendix B: Materials: What’s needed...
 Appendix C: Project expenses

Architectural photodocumentation using rectified photography
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00103301/00001
 Material Information
Title: Architectural photodocumentation using rectified photography
Physical Description: Archival
Language: English
Creator: Blackey, Dorinda K. M.
Publisher: Dorinda K. M. Blackey
Place of Publication: Gainesville, Fla.
Publication Date: June 30, 1983
Subjects / Keywords: Historic preservation
Architectural photography
General Note: UF course ARC 6713
General Note: UF AFA Historic Preservation document 283
 Record Information
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
System ID: UF00103301:00001

Table of Contents
    Title Page
        Page i
    Table of Contents
        Page ii
        Page iii
    Photodocumentation: The uses, the technology and the application
        Page 1
        Page 2
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
    Case study: Maitland Art Center
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
    Analysis of the case study
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
    Appendix A: Rectified photography in the field
        Page 28
        Page 29
    Appendix B: Materials: What’s needed in the field
        Page 30
        Page 31
    Appendix C: Project expenses
        Page 32
        Page 33
        Page 34
        Page 35
Full Text
44 t/.i /It
kr?/A /




Dorinda K. M. Blackey
University of Florida
ARC 6713
June 30, 1983.



PREFACE . . . . . . . . . . . . . .

THE APPLICATION . . . . . . . .




STEP CHECKLIST . . . . . . . .



FOOTNOTES . . . . . . . . . . . . .

BIBLIOGRAPHY . . . . . . . . . . . .

. iii

. 1

S. 2

. 22

. 28

. 30

S. 32

S. 34

S. 35


This paper is written in conjunction with an ongoing project of record-

ing a building, the Maitland Art Center, photographically. The intent of

this project is to understand the technique of photodocumentation and

rectified photography and to produce accurate drawings of details of the

building using this photographic process.

The intent of the paper, in relation to the project, is to outline the

research necessary, to explain the process used, and to analyze the method

and its results. For this reason, the paper follows a three-part format.

Part 1 is a general explanation of photodocumentation and its advantages and

disadvantages. Part 2 concerns itself with the actual step by step process
of photo aumentation which was used in this process from photo survey to

finished drawing. It includes a thorough explanation of the process of

rectified photography. Part 3 is an analysis of rectified photography as it

was applied to this project, not only in terms of accuracy, but in efficiency,

as well.



Photodocumentation is the process of recording an existing structure

with photographs. This method of documentation involves taking a photograph

of a building at a predetermined architectural scale which is free of perspec-

tive distortion. The photograph is then used in place ofor in conjunction

with, the traditional hand-measured drawing as a document of the building.

The document can be utilized in any of a number of ways. It can be used

as a permanent, historic record of a significant structure. It can be used as

a part of the contract documents on a project involving rehabilitation, restora-

tion or compatible design. Photodocumentation, however, should be used only as

part of the documentation process. Plans must still be hand-measured and drawn.

Certain parts of structures, also, may not be suitable for photographing due to

location, lighting, foliage or design.

Documentation with photographs is more appropriate for some buildings than

for others. According to Harley McKee in Recording Historic Buildings, photo-

graphs can be used most appropriately in documenting:

--buildings which are relatively simple and of secondary importance;

--buildings which are of a repetitive nature like factories;

--details on a building which are extremely elaborate and difficult to

document with hand-measured drawings.1

Mr. McKee's use of photographs falls short of its potential, however. The

detailed, hand-measured drawing should be used for the "significant" structure


as Mr. McKee implies. Drawings, however, lack certain qualities of a building

which can only be recorded in photographs. In such instances, it seems that

not only are hand-measured drawings justified, but photodocumentation is, as

well. Photodocumentation2alsocan be used when certain aspects of recording

are not as stringent.

Certain buildings, however, are not very photogenic in terms of documen-

tation. Perspective distortion limits the photodocumentation of buildings with

curvilinear surfaces and with complex planar surfaces.

The photodocumentation process beings with an assessment of the type of

photo survey needed. The choice is based on the intricacy of the building

detail, the accuracy of the photograph required, the level of technology and

equipment available and, of course, the time and budget allotted.

The actual photo survey can be conducted in several different ways using

photogrammetry. Photogrammetry is the technique of photographing an object

to yield its measurements to a certain degree of accuracy. The degree of

accuracy needed for an individual project determines the method used.

Certain projects require not only extremely accurate photographs, but

also extremely detailed ones. Stereogrammetry is the technique which would

be used in such a case. Usually the project involves a highly ornamented

building which cannot be recorded by hand. Louis Sullivan's Chicago Exchange

Building was such a project. The entrance to the building with its rich and

intricate Sullivan details was impossible to record by hand. Before the build-

ing was destroyed it was recorded using stereogrammetry (see figure 1).

Stereogrammetry is a very complex and technical type of photogrammetry. It

entails two simultaneous cameras set up.with special equipment. The result is

"a three-dimensional projected or optical model which can be scaled or measured

in all directions." A plotting machine translates this "stereopair" into an

orthographic projection.

Figure 1


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The process is quite complex and requires access to expensive and com-

plex machines. Its accuracy and ability to transfer photographs to drawings

make it very valuable as an architectural recording tool, however. The

economics of it must be justified by the structure to be recorded.

Another method of recording a building is mono-photogrammetry. This

term applies to any single photograph technique of quantitatively recording

a building. It includes one method in which a drawing is done by doing

reverse perspective calculations from a photograph. It also includes a tech-

nique where a photograph with perspective distortion is corrected in the dark-

room by a complex enlarger called a rectifier. What is commonly called

rectified photography also comes under this heading. It is the production

of a single photograph which is essentially free of perspective distortion.

There are a couple of different methods to achieve this distortion free

photograph. The focus of this study was these methods of photogrammetry

and their application to the photodocumentation process. Therefore, a more

detailed explanation of rectified photography is contained in Part 2.

In some projects neither distortion free photographs nor quantitatively

precise photographs are needed. In these cases photographs are used as field

notes to explain existing conditions and to denote changes required. The only

requirements for this photographic process is that the photographer take them

on an overcast day or out of the sun. Strong sun creates dark shadows which

hide details. This straightforward photograph should also keep in mind basic

principles to minimize distortion and scale deception.

Once the decision has beenmade as to the most appropriate type of photo

survey and it has been conducted, the actual process of photodocumentation



The photodocumentation process can be done using either of two methods.

One method uses a photo-sensitive transparent drafting film. The photographs

of the building to be used are selectedas well as any drawings. The drawings

are photographed, and then the entire sheet is played out. Negatives are made

at an appropriate size so that contact prints can be made. The negatives are

assembled on the photo-sensitive film and a contact print is made. The con-

tact print should be made on the back of the drafting film so that any addi-

tional drawtpr written information can be applied to the front side. It

should be noted that the negatives should be, therefore, printed in reverse

so that when the film is turned over the images are correct.

A slight alternative to this method is instead of producing several

individual negatives, the photographs can be laid out and a single large nega-

tive produced and contact printed. Either way, the result is an effective,

relatively permanent "sheet" capable of innumerable reproductions. The method

is expensive. One office estimated a cost of $35.00 per sheet for the produc-

tion. From the office standpoint, however, this is very inexpensive when

compared with the cost of the labor involved in a drawing of the same thing.

The other method of producing a photo-documented sheet involves more

accessible equipment and materials. With this technique a photocopy machine

is used. As in the previous method, photographs and drawings are selected and

the drawings photographed. The sheet layout is designed and the size and scale

of the photographs determined. The photographs are then printed at the appro-

priate size, but in reverse so that when they are later applied to the back

side of the drafting film the images will be correct. The reversed prints are

then copied on a good quality photocopy machine. A half-tone screen is

recommended for the copying. The copies are made either onto clear acetate

or onto adhesive drafting film. It is necessary with some machines to spray


a fixative to prevent smudging of the copied image on the film. The excessive

film is trimmed from the copy and the copy is applied to the back side of the

tracing sheet. In the case of the clear acetate copy a spray adhesive is used

and with the adhesive film the backing is just peeled away. As in the other

method, any additional drawings or notations are applied to the front side.

The sheet is then ready to be printed in the diazo machine.

The advantage of this method is that it allows for everything to be printed

separately, allowing for individual exposure needs of images. Secondly, it

allows one to erase part of the image at any time. One can erase to highlight

a line or erase a half of a facade to be able to draw a planned addition. It

also is a very accessible and inexpensive process. The disadvantage of this

process is that.reportedly, the adhesive film peels off in the diazo machine.6

The advantages of photodocumentation are numerous. As was mentioned

earlier, certain qualities of a building cannot be communicated in a drawing.

The measured drawing is primarily a quantitative recording while the photograph

is a qualitative recording. The effects of light and landscape on a building

are not recorded in a drawing, but are very important.

As part of the contract documents in a project, photodocumentation elimi-

nates confusion. The client and the contractor can more readily understand a

photograph than a drawing. This clarity adds to the desire of contractors to

bid on a restoration project. The specific aspects of the job are much easier

to discern. If the project is under review by a government agency, photodocu-

mentation's specificity and clarity often encourages a faster processing. The

photodocumentation eliminates all of the problems inherent with individual

interpretation of drawings.

To the architectural office using photodocumentation in contract docu-

ments means a savings in time. Different offices have recorded extreme savings


in the production time. One office noted a 50-90% savings in time per docu-
mented sheet. Another office pointed out that handcrafted drawings of a

standard format of architectural details took 80-150 manhours, while photo-

documentation could take an optimistic 24 hours. This same office noticed a

reduction in the documentation phase from 6 weeks to 5 weeks, less than 3
of which were to do the drawings. The increased accuracy in details yields

long-term efficiency and savings to the office, as well. Finally, better

communication with the client and the contractor always increases efficiency

for the office.

The disadvantages of using photodocumenation arise if the limitations of

the photograph are not respected. The reality of the photograph is deceiving.

The distortion of perspective and limitations of a two-dimensional represen-

tation of a three-dimensional object are inherent problems in the photograph.

The photograph appears so realistic that these problems are often ignored.

The disadvantage to the architectural office in using photodocumentation

is that the scope of the project must be defined early, so that all necessary

aspects can be photographed. It is difficult to make additional photographs

later and almost impossible to incorporate them into the ongoing document

preparation which is using other photographs. Photodocumentation does not

have the same degree of flexibility as handcrafted drawings. Also, if the

photo/print process cannot be done in-house, then that means they must be

contracted out. This means working with an outside company which also limits

flexibility, especially in deadlines.



The Maitland Art Center, located near Orlando, Florida, had been docu-

mented by students of the College of Architecture at the University of

Florida. Hand-measured drawings were done of the complex, but a few of the

sheets had not been completed. Space on the sheets had been allocated for

details of the building which time had not permitted to be documented and

drawn. This present project began as an attempt to complete those sheets.

The details of the building were too complex and curvilinear to measure

by hand for documentation. Some method of photogrammetry seemed in order.

Because of the limitations of the equipment available, a type of monogrammetry

was decided upon. Rectified photography was chosen as the method to be used

because a certain degree of accuracy was necessary as these drawings were,

in part, being done for the Historic American Buildings Survey (HABS).

Rectified photography is "the representation of plane surfaces photographi-

cally to produce an elevation of that surface with no appreciable distortion
of scale in any selected direction." It was believed that from these eleva-

tions enlargements of the details could be printed. Tracings could then be

done of the prints onto the partially completed sheet.

In an office situation, it would be typical not to trace these photo-

graphs of the details but to print the photograph directly onto the "sheet."

Therefore, the process of photodocumentation was researched as part of this

process. As there was no previous exposure to rectified photography, the


research and learned application of it became a major portion of the project.

Photodocumentation seemed an ideal medium to illustrate this research.

The Photo Survey

The first thing to be done was to decide upon the details to be photo-

graphed and, eventually, traced onto the HABS sheets. These were selected

based upon their relationship to the elevations which occupied the partially

completed sheets. To better understand the process of rectified photography,

it was decided to photograph not only the details, but also to photograph the

entire elevations represented on the sheets. The rectified photographs of the

elevations could then be compared to the drawings to determine the accuracy and

efficiency of rectified photography. The photo survey became a two part project.

One was to gather the detailed photographneeded for the drawings. The other

was to photograph the elevations in an attempt to understand and analyze the

capabilities of rectified photography.

To rectify a photograph is to remove perspective distortion. This is best

done by making the plane of the camera lens parallel with the plane of the

building (see figure 2). The planes must be parallel in both a vertical sense

and a horizontal sense. This is done by placing targets strategically on a

building. These targets eventually must line up with a grid seen through the

camera lens.

Placing the targets on the elevation was critical in this project. The

targets must be on the same plane. The protrusion of even a window sash will

lessen the accuracy. The placing of the targets was planned in advance on

paper. Prints of the elevations were used to place the targets. Normally,

one would begin by placing the first target in the center of a building. Then

targets are positioned to the right and left of the center target at an equal

spacing usually of a ten foot module. Then targets are placed directly below





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these two outer targets at the same spacing to form a retangle (see figure


In this case, instead of the center of the entire elevation being located,

the center of the portion of the elevation to be photographed was located.

The portion of the elevation to be photographed was determined by whether or

not there was a single plane which could be used to place the targets. The

center target's position was recorded on the printed elevation. The targets

to either side were placed at 15 feet because that was a satisfactory position

down the entire series of the west elevation in that there was no protrusions

or depressions every 15 feet. Targets were marked off 5 feet directly below

the outside targets. Five different elevation shots could be taken according

to this target placement. Ideally, one would shoot one photograph of an entire

elevation. In this case, the elevation was too long.

The placement of the targets can be very tedious and frustrating. Even

the best planned positioning of targets can be foiled by unexpected shrub or

tree trunk. In this case, that was true. All of the careful planning at the

drafting table was futile. When the targets were actually placed on the build-

ing, many of them were completely obstructed by the shrubbery.

One reference noted that three targets could be sufficient in rectifying

the photograph if they were placed perfectly horizontal to one another. With

this in mind, some of the photographs were attempted in exactly this way. Since

the shrubs obliterated the lower targets, the upper three targets were all that

was visible. Three targets will determine horizontal parallelism. To get

vertical parallelism a true vertical element must be established on the build-

ing. The camera is kept vertical if the vertical lines of the camera grid are

true to this true vertical element.


F_ I fl




The position of the camera is determined by several things. For one

thing, the size of the object to be photographed influences the location of

the camera. The scale at which one would like to photograph this object can

determine the camera position. By the same token, the distance the camera

can be moved back can determine the size of the object to be photographed.

The focal length of the lens, also, is in direct relationship to the camera

location. These relationships can be expressed mathematically in this ratio:


I = Size of the image

F = Focal length of the lens

G = Size of the object

A = Distance between object and lens

Graphically, this relationship can be seen in figure 4. Therefore, to deter-

mine the camera distance from an object (A), the size of the image must be

known (the size of the negative); the focal length of the lens must be known;

and the size of the object must be known. With the camera a calculated distance

away from the object the negative can be at a designated architectural scale and

printed accordingly.

In this case, a 4 x 5 view camera was used with a lens which had a focal

length of 4.5". The size of the portion to be photographed was 40'-0". The

negative of a 4 x 5 camera is 4" x 5". At 1/8" scale, 40'-0" equals 5".

Therefore, 1/8" scale is the largest scale which could be used. To take this

negative so that it will be at 1/8" scale, the following calculation is done.

The object size is actually the spacing of the targets as that is what is being

focused on. This distance (A) is 30'-0" (360") in this case from outside target

to outside target. The image size which is that target spacing at 1/8" scale

or 30'-0" at 1/8" scale is 3.75".

If: I G

Then: A = F(G)

Therefore: A = 4.7"(360")
3.75" = 37' 7 1/4"

So if the camera is set up 37'-7 1/4" away from the wall, an image will be pro-

duced at an 1/8" scale.

With a target plan prepared and the necessary calculations complete, the

actual project can be undertaken. The day the photographs are taken is prefera-

bly an overcast day. If not, try to photograph each facade when it is not in

full sun to minimize loss of details in shadows. Gather together the day before

everything that might possibly be needed for the excursion (see Appendix B)

including anything which might seem only remotely necessary. If the location

is a great distance away, it is better to be safe than sorry. Allow more time

than is necessary to complete the project. Such projects always take longer

than expected. A minimum of two people are needed to perform the exercise. A

general system of notes and recordings is strongly recommended (see Appendix B).

Not only is this sound practice, in general, it may facilitate an unforseen

return visit in the future.

To begin with, on the site, the vertical center line of the building is

found by measurement. A line perpendicular to the building plane and at the

center line must be determined. This can be done by swinging two equal arcs

equal distance from the center line. By connecting their point of intersection

with the vertical center line of the building, a perpendicular line is found

(figure 5a). Triangulation can, also, be used which was the case in this project

Based on the fact that a right triangle's side will always be in a relationship

of 3, 4 and 5, 3 strings were cut. One was 6 feet long, one 8 feet long and

one 10 feet long. The 6 foot long string was stretched from point A to point B






(see figure 5b) and point B marked. The 10 foot string was stretched from

point B and the 8 foot string from point A. Where the ends of the two strings

met was point C. A stake was placed to mark the spot. Over this point a

transit was erected.

The transit is used for two purposes. One is to place the targets on the

building. The other is to situate the camera. The first target placed is the

center target which is on the vertical center linea pre-determined distance

up from the ground plane. Its positioning is done by measurement and the use

of a plumb bob. The targets to the left and right of the center are positioned

horizontally with a transit. The cross-hairs of the transit are positioned to

cross the center of the target. The lower targets are placed by measuring down

the pre-determined distance and accurately placed by using the plumb bob. Be

sure that the targets are securely fastened and won't blow in the wind. Con-

sideration as to the fastening device should be done ahead of time. Masking

tape won't hold on many surfaces.

The camera is set up on the same perpendicular line as the transit. This

is done by turning the transit 1800 from the center target. The transit cross-

hairs should cross the center of the lens. The camera should be away from the

wall the calculated distance, in this case 37'-7 1/4". The height of the camera

should be as close to half the height of the building as possible. Record the

camera height. The transit can be taken down now.

A 4 x 5 camera has a ground glass on the back through which one looks

through the camera. This 4" x 5" piece of glass should be marked off in a 5/8"

grid. The lines of the grid should not intersect, but should meet as a point

(see-f-ig~re='). The camera is adjusted so that the targets on the building are

at the intersections of the grid. If three targets meet, that is close enough.

It must be assumed that in such a case the fourth target must have been put up


incorrectly. Figure 7 shows potential problems in lining up the target with

the grid.

With the targets lined up with the camera, everything is ready to be

photographed. The focus should be rechecked and locked into place. The ground

glass back is then removed from the camera and replaced with the film back. In

this case, the film back was a special Polaroid back, specially designed for

Polaroid film. Polaroid 4 x 5 Land Film, Type 55, was used for this study.

The reason for this was that this film type produces,instantaneousjboth a posi-

tive and negative of the image photographed. With an immediate image available,

the results of the photograph can be checked. If another exposure is necessary,

it can be taken on the spot. With regular sheet film development takes place

later in the darkroom. A bad negative in that case means returning to the site

and resetting of targets and camera.

Another reason the Polaroid film was chosen was that the negative develop-

ment of sheet film is extremely time consuming if specially designed equipment

is not available as was the case with this project. The entire development

process must be done in total darkness, one sheet at a time. To have the nega-

tive developed commercially raised the cost of regular sheet film to equal the

price of the more expensive Polaroid film. For the same price, one can have

photographic results in the field. Polaroid makes another 4 x 5 film which only

produces a negative. There is enough information from the negative that the

positive is not necessary.

Once the photograph is taken and the results checked, the negative is

stored suspended in a sodium sulfite solution. It is stored like this until

it can be properly washed and dried. The negative can then be used to make

prints following normal methods.

All of the elevation shots were taken following the same procedure. Shrub-

bery, trees, and a variety of plants were the greatest handicap in photographing


the art center. Originally, the intention was to do rectified photographs of

the entire west elevation. The photographs could then be made a mosaic and

compared to the drawings of the west elevation. These handicaps prevented

that from being possible. In fact, there was only one portion of the wall

that could be photographed following this method exactly.

The other part of the photo survey was to photograph the details of the

building. The same method of finding the camera position for each detail was

followed. In the case of details, the scales at which the photographs were

tkane varied being either 3/8" scale or 1/2" scale. The detail shots did not

use targets. Instead the lines of the detail are oriented to the grid of the

camera. A small level was used to assure that the camera was level in all

directions. A surveyor's range pole was included in the photograph to aid in

the measurement of the details.

With the range pole included it actually would not have been necessary

to scale the negative. The pole which is marked off in feet would have pro-

vided the necessary information. From it, an enlargement could have been made

at a desired scale by having a one foot increment on the pole equal the desired

scale when seen through the enlarger. For instance, if a detail needed to be

reproduced at a scale of 1"=1', the negative could be enlarged in the enlarger.

When the point was reached that a one foot increment on the pole equalled one

inch, the print could be made. This method is actually more accurate than

using the calculations to get the scale. In the field, it is difficult to get

the precise measurements necessary with that method.

The use of the range pole can also be applied to elevation shots. A pole

marked off in foot intervals placed at either end of an elevation can be used

to achieve the desired scale in the darkroom. With this method, the camera is

set up at any distance away from the building. The camera back must still be

parallel to the building. To assure this, dividers are used to check the size


of the range poles through the ground glass. The camera is parallel when the

range poles on either side of the elevation are equal. Vertical parallelism

by finding a true vertical element and orienting it to the grid and by using a

level on the camera. Further rectification can be done in the darkroom.

Unfortunately, this method was not tried with this project.

The remainder of this survey was done for academic purposes. All of the

photographs taken with the 4 x 5 camera were also taken with a 35mm camera.

This was done to compare results of the two different cameras. The 35mm camera

was also used to take a snapshot series of the entire west elevation. Again,

this was purely academic. The purpose was to illustrate a "normal" amount of

distortion when photographing a building. The accuracy of rectified photo-

graphy could be comapred to this "normal."

The actual photographing was done in two, very long and intense days.

The Darkroom Work

The negatives were printed in a standard way. The scaled negative, ideally,

would be used in an enlarger that will designate the percentage of enlargement.

Since this was not available, the enlarger was adjusted until the size of the

photograph was double the size of the image. A 4" x 5" negative was enlarged

to an 8" x 10" format. If the negative was taken at 1/8"=1' scale, then this

should produce a print at a scale of 1/4"=1'. In actuality, this was not the

case. A pring at 1/4"=1' scale was about 6 3/4" x 8 3/4". The reason for this

is that only a portion of the negative is printable. The actual usable area of

a 4" x 5" negative is about 3 5/8" x 4 1/2". The other reason for the dis-

crepancy is that in the field it is extremely difficult to set the camera lens

the exact distance away from the wall.

To print the negatives at exactly 1/4"=1' scale, the information on the

detail negatives was utilized. The range pole made certain dimensions known.


These dimensions at the appropriate scale were applied to the elevation nega-

tives. They were enlarged accordingly and printed.

The details were printed in the method previously described. Two of the

detail shots proved to be not rectified vertically. To correct this distortion,

the easel of the enlarger was tilted. When all lines were parallel, the tilt

of the easel was recorded and the print made. Some enlargers have easels which

are easily adjusted and the angle of the tilt described. The enlarger used in

this case did not, but the results were the same. When the easel was tilted,

the enlarger was stopped down as far as possible to maximize the depth of


A filter was used to increase the contrast in the print. The advisability

of this is questionable. The increased contrast may have removed some of the

weaker detailing in the shadows. The intent of these photographs is to reveal

as much as possible about a building. Any aesthetic qualities should be

sacrificed to this intent.

In this case, the photographs were printed on Kodak Polycontrast F paper.

There is a photo-sensitive mylar onto which the photographs can be printed.

If this material was available, it would have eliminated a step in the photo-

documentation process.

The Transfer to Diazo

For the purposes of analysis and presentation it was desirable to transfer

these photographs to the hand drawn sheets of the art center. These drawings

had been done on drafting film. To combine the drawing and the photograph onto

one sheet, the photodocumentation process was utilized. Tests proved that plain

acetate sprayed with adhesive was more effective than self-adhesive drafting

film. In the first place, the photograph came through the diazo machine

clearer on the acetate. Secondly, the acetate copy printed the image correctly.


The adhesive film copied in reverse. To use adhesive film the photograph

would originally have to be printed in reverse so that when it was copied it

would be correct.

The elevation photographs were photocopied onto the acetate. With spray

adhesive the copies were mounted on the back of the drafting film on which

the drawings were. This sheet was then run through the diazo machine. A

black-line print of the photograph and the drawing were the result. The

acetate copy was easily removed from the back of the original sheet with a

generous application of rubber cement thinner and a paper towel. The photo-

copied acetate is sacrificed by this removal.

The diazo prints were then used to analyze the accuracy of the rectified

photographs with the hand-measured drawings.



The photographs which were taken as part of the photo survey for the

Maitland Art Center were compared with the drawings which had been done of

the Center by the University of Florida students. In general, the assumption

is that the drawings are correct. Any variations suggest failure on the part

of the photograph. Here are a couple of instances when it is known that the

drawing is incorrect.

Photograph #1 (Figure 7)

The greatest discrepancy seems to be in the vertical direction ranging

from 4.2% to 8.4%. In this case, there seems to be inaccuracy in recording

the ground plane. When the measurements were taken for the drawings, the

complex was completely overgrown with foliage. Accurate information about

the ground plane may have been inaccessible. The variation in measurements

in the horizontal direction raises a couple of possible explanations. One

is that this photograph is printed at the wrong scale. The enlargement was

not just double in size as the procedure dictates; instead the enlargement

was adjusted in the darkroom. The dictated scale of enlargement made the

targets, which are 8 1/2" x 14", the wrong size. Therefore, the enlargement

was adjusted until the targets were 8 1/4" x 14" at a scale of 1/4" = 1'O".

Why this would make everything else wrong is not known.

The other possible explanation is that the drawing is not correct. One

thing that supports this theory is that the relief is not drawn at the proper

size according to a detailed photo taken of the relief.

Photograph #2 (Figure 8)

This photograph will not be completely rectified because there are

several plane changes in the building at this point. Secondly, only three

targets were used for rectification.

In general, there is a lot of agreement between this photograph and

drawing. The discrepancies are rather predictable.

The far left side of the elevation projects out about 6". This causes

the photograph to record this plane at an enlarged scale. All of the measure-

ments of this area are larger in the photograph than in the drawing. This

plane of the photograph is not rectified.

Point I reveals the most significant percentage difference. The reason

for this large discrepancy is two-fold. One, the roof is pitched. A receding

plane cannot be rectified. Secondly, the roof sags horribly. The measurement

for the drawing could have been taken at any point.

The other discrepancies is in the openings--the doorway and the window-

type opening. It seems strange that there would be a variation because the

columns in this same area show no discrepancy.

The use of three targets does not seem to have affected the rectification.

One source said that only three targets were necessary as long as vertical

rectification was achieved somewhere else. This was the case in this instance.

Photograph #3 and #4 (Figure 9)

Photograph #3 and #4 were both taken with three targets and both have

several plane changes with their portions of the elevation. The vertical

rectification was taken from the building itself, rather than using five

targets. Generally, this does not seem to have affected the results. The

plane changes predictably cause discrepancies (Points A, B, H, J). Places

which are on the rectified plane show little or no variation (Points C, I, G).


The vertical variations could be due to not using five targets with the

exception of the central figure in Photograph #3. It is known that that was

drawn incorrectly. In Photograph #4 there is little or no discrepancy on the

rectified plane, however, the receding plan reveals its inability to be



1) The use of five targets assures the vertical rectification of the

photograph. However, three targets are probably adequate in many cases.

2) This method best serves its purpose on a building with basically one

plane per elevation. However, in many cases, one plane may be more critical

than another and it might be worth having the one plane rectified and scaled

at the least.

3) The other method of using the rods and the dividers on the grid would

be easier to set up. This would do the same thing that the three targets did.

And the true target method proved fairly accurate.

4) Both the drawings and the photographs should next be compared with

measurements taken from the building. Both will reveal discrepancies. It

would be interesting to note which had the higher percentage of discrepancy.

In general, the method was very tedious and frustrating to do. This is

probably due to the self-teaching aspect of the project. If there had been

outside instruction, simple techniques would not have seemed so complicated.

The final results were better in some ways than anticipated.

As a part of the preservation documentation process, rectified photo-

graphy and photodocumentation are valuable. They must be understood for their

limitations, but the information they afford outweighs any drawbacks. With

time and practice, the inaccuracies and inconveniences could be removed, too.


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Target Method

1. Find center line of elevation and mark.

2. Set up transit perpendicular to the center line. Use arc method or


3. Place center target on center line and up predetermined distance.

4. Level transit to focus on center target.

5. Position other two top targets with transit.

6. Place lower targets by measurements from upper targets and use of a plumb


7. Set up camera on same perpendicular line as transit and at calculated

distance out.

8. Line up ground glass grid and targets.

9. Record camera height. It should be 1/2 building height.

10. Set exposure, focus and take photograph.

11. If using Polaroid film, store negative in sodium sulfite solution.

Range Pole Method

1. Find center line of elevation and mark.

2. Find line perpendicular to the center line. Use arc method or triangular.

(Possible to use an instrument called an optical square.)

3. Place camera anywhere desirable or feasible along this line.


4. Place range poles at either end of elevation. Use level to assure


5. Looking through ground glass grid adjust camera by panning until range

poles are of equal size. Use dividers to check size.

6. Check verticality.

7. Camera height ideally should be 1/2 of building height. Record height.

8. Set exposure, focus and photograph.

9. If using Polaroid film, store negative in sodium sulfite solution.



1. Camera. Large format camera is desirable, either a 4 x 5 or an 8 x 10

format. A view camera that has vertical and horizontal adjustments is

nice. There is a lens made for a 35mm camera which makes perspective

corrections, however, the 35 mm camera does not afford the view of a

4 x 5 camera. The ground glass area of a 4 x 5 camera is invaluable

in this process. The level of detail achieved by a view camera is

better than the 35mm camera. Lens type varies with the application.

2. Tripod. A good, heavy tripod is needed. If your camera does not adjust

vertically and horizontally, the tripod must.

3. Transit. A surveyor's transit with plumb bob and tripod.

4. Range Pole. One with tenth of an inch increments and one with just one

foot increments.

5. Film. Always bring plenty.

6. Levels. A small level which will work on the camera. A torpedo level

will, also, work on a rod level. A larger level to check range pole.

7. Targets. Targets are made by taking black construction paper and cutting

two rectangles 4 1/4" x 5 1/2". These are glued onto a sheet of 8 1/2" x

11" paper in diagonal corners. The result should be 4 rectangles, 2 white

and 2 black, each 4 1/4" x 5 1/2". Xeroxes of this can be made as needed.

8. Tape. A heavy, extra-strong tape to hang the targets.

9. Nails and Hammer. In case the tape doesn't hold.

10. String. To do arc method or triangulation.

11. Stakes.

12. Ladder.

13. Sodium Sulfite. Negatives must be hund in this solution. A tupperware-

type container that is deep and has a lid is good.

14. Clips. To hang negatives from string in solution.

15. Notebook/Data Sheets. To make recordings.

16. Towel. A dark towel thrown over the view camera increases visibility.

17. Measuring Tapes. A 20' and a 100'.

18. Calculator. For last minute calculations.

19. Hedge clippers, saw. Of course, permission must be granted to use on

foliage, but sometimes trimming one small branch may help make that

target visible.

20. Chalk line and stick-type chalk.

21. Appropriate personal gear and amenities. Hats, foul weather attire, coolers

of liquid refreshment, coffee.....Depending on the climate such amenities

will help to shorten a long day of work in either hot or cold weather.



Film: Polaroid, Type 55 (1)................................$ 33.00

Tri-X 135 (2)........................................ 7.00

Chemicals and Paper*...................................... 47.00

Slide processing and miscellaneous lab work................. 9.40

Photo copies..................................... ........ 7.00

Diazo prints............................................ 5.00

Presentation materials.................................... 14.50

Trip expenses (3) .......................................... 50.00


*Fortunately, some of the large 11 x 14 paper was donated.



McKee, Harley. Recording Historic Buildings. Washington, D.C.
National Park Service, 1970, p. 40.

Lowey-Ball, Roy and Gilson Riecken. "Photodocumentation and Restora-
tion Work." Architectural Record, Vol. 163, March 1978, p. 71.

Phiffer, Cynthia J. "Contract Documents on Restoration Work." AIA
Journal, Vol. 65, February 1976, p. 47.

4McKee, op. cit., p. 42.

Leslie Divoll and Chalmers Yielding. Notes from a conversation with
these two architects who have used photodocumentation process and rectified
photography in their offices.


Hockey, William B. "Scaled-Rectified Photography on Site." Bulletin
of Association for Preservation Technology, Vol. 7, No. 3, 1975, p. 38.


Application of Photogrammetry to Historic Monuments. Paris: International
Council of Monuments and Sites, 1968.

Borchers, Perry E. Photogrammetric Readings of Cultural Resources.
Washington, D.C.: National Park Service, 1977.

Chambers, J. Henry. Rectified Photography and Photo Drawings for Historic
Preservation. Washington, D.C.: National Park Service, 1973.

Davis, Phil. Photography. Dubuque, Iowa: William C. Brown Co. Publishers,

Hockey, William B. "Scaled-Rectified Photography on Site." Bulletin of
Association for Preservation Technology, Vol. 7, No. 3, 1975.

Lowey-Ball, Roy and Gilson Riecken. "Photodocumentation in Architectural
Restoration Drawings: An Economic Technique Adds Flexibility and
Accuracy." Technology and Conservation, Vol. 77, No. 4, April 1977,

"Photodocumentation on Restoration Work: A New Technique That
Lowers Cost, Saves Time and Maintains Control." Architectural Record,
Vol. 163, March 1978, pp. 71-73.

McKee, Harley. Recording Historic Buildings. Washington, D.C.: National
Park Service, 1970.

Phiffer, Cynthia J. "Contract Documents on Restoration Work." AIA Journal,
Vol. 65, February 1976, pp. 44-47.

"Photographer's Mate 3." Bureau of Naval Personnel, Navy Training Course-i
(NAV PERS 10373-A). U. S. Navy, U. S. Government Printing Office,
Washington, D.C., 1961.

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