Re: Digital Camera & IR

[Andrew Davidhazy <ANDPPH@xxxxxxxxxxxxxxxxxx>]

> I want to test IR features about an Agfa 780 digital camera... I can shoot
> with or whiteout filters ? And..the filters is the normal red or
> others....some tips ?

Daniele,

I did a similar test with an Agfa 1280 and the results are summarized below.
To see the illustrations you can do so on the web at the following address:

             http://www.rit.edu/~andpph/text-agfa-1280-ir.html

        Infrared Photography Experiment with Agfa ePhoto 1280 Camera
                                      
                              Andrew Davidhazy
                    Imaging and Photographic Technology
                  School of Photographic Arts and Sciences
                     Rochester Institute of Technology
                                      
                                Introduction
                                      
This is simply a brief report, illustrated with a set of photographs, designed
to demonstrate the capability (or lack thereof) of the Agfa ePhoto 1280 camera
to record images in the near infrared.
                                      
About a year ago I acquired an Agfa 1280 camera and among the first things I
decided to try was to find out if the camera had any residual infrared
sensitivity by which images in the near infrared could be recorded. All
indications at the time were that the camera was very well filtered to
eliminate infrared from the CCD sensor and even when I flashed an electronic
flash directly into the lens which was covered with an 87C filter, the sensor
produced a barely detectable image on the camera's LCD screen.
                                      
The result of this somewhat cursory experiment was rather discouraging in terms
of being able to use the camera for near infrared photography but it was
reassuring to know that the infrared was well filtered out and did not
contribute at all to the capture of standard color images. I concluded at the
time that the 1280 was quite unsuited for near infrared photography.
                                      
Follow-up experimentation
                                      
Then, in August or September of 1998 someone posted a message on a mail list
about the fact that Eric Cheng, a student at Stanford University had used the
1280 for infrared photography. I checked out the website where the images were
shown. They indeed showed images that bore unmistakable characteristics of
having been made by infrared, rather than light, wavelengths. The photographs
were mostly all outdoor scenes taken in what appeared to be broad daylight and
with full sunlight falling on the scenes. This is something I had not attempted
and decided to try to duplicate the sample images.
                                      
[ result with no filter over camera lens] [ result with wratten 87 over camera
lens] [ result with wratten 87C over camera lens] 
                                      
Left: no filter shown in color Middle: Wratten 87 Right: Wratten 87C
                                      
Sure enough, when the 1280 was aimed at a sunlit scene and the lens covered
with a Wratten 87 filter, a dim reddish image showed up on the LCD panel.
Subsequent to making an exposure the image on the screen looked quite
acceptable. With a Wratten 87C, if one switched to manual exposure setting and
cranked up the exposure to the maximum, even then the image on the LCD screen
was quite dark or sometimes was not visible at all. Also, the image was no
longer red but was a neutral grey tone and looked rather dark. Upon making the
exposure things did not really improve in terms of the quality of the displayed
record. This was possibly due to the fact that the exposure for previsualizing
was as high as it could get for actual exposure whereas with the 87 filter one
could get a general idea of the view through the filter and then the camera
would make the final exposure adjustment at the time it made the record which
then looked quite a bit brighter then the preview.
                                      
When these images were donwloaded and opened up in Photoshop, it was possible
to make rather acceptable reddish images of the photographs made through the 87
filter. When the color was discarded and some basic tonal adjustments were
made, the greyscale record was quite good and exhibited the typical light-toned
vegetation and dark skies associated with an infrared reproduction. The images
made with the 87C filter needed a significant amount of manipulation of levels
with Photoshop. This boosted the noise level of the images and gave them a
rather unacceptable grainy and fuzzy appearance.
                                      
In addition to the noise generated by trying to extract an image from the
limited amount of data recorded by the sensor, the camera seemed to lose its
ability to focus automatically, and in close-up work in particular, the images
were less and less focused the deeper the infrared filter that was used. This
is illustrated below.
                                      
[ result with no filter over camera lens] [ result with wratten 87 over camera
lens] [ result with wratten 87C over camera lens] 
                                      
Left: no filter and shown in B&W Middle: Wratten 87 Right: Wratten 87C
                                      
Conclusion
                                      
All in all my experience supports the fact that the residual infrared
sensitivity of the Agfa ePhoto 1280 camera's CCD sensor is high enough that
when either the camera's autoexposure program or the manual exposure settings
are used, and given plenty of infrared such as in an outdoor scene illuminated
by full sunlight (especially in the summer), a decent infrared record can be
made. This is particularly the case with the less extreme filters such as the
Wratten 87. Under extreme conditions of flash or tungsten illumination it may
also be possible to secure a useable image especially if one only uses a
Wratten #25 or #29 deep red filter.
                                      
Further experiments along these lines will be conducted and they will result in
this report being updated as their outcomes become available.
                                      
If you have questions or want to discuss any aspect of Agfa ePhoto 1280
applications feel free to write to me at andpph@xxxxxxxx


Andy  o o  0 0 o . o  Andrew Davidhazy, Imaging and Photo Tech
       \/\/\/\/\/\/   http://www.rit.edu/~andpph  716-475-2592  
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