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Photo Forum / Film Photography / Film and Labs / June 2004Problems when developing color photographs?
I have some aerial photographs of the same areas. They are shoot within 15 min, the focal length, aperture stop, exposure time etc. are fixed and therefore the same for all the photos. The problem is that some of the images are very different in color (some bluish other yellowish). Is there anywhere in the developing process that cause these big differences? Any suggestions and ideas are appreciated. Regards /Morten Nielsen Email: http://www.iter.dk/contact.aspx > I have some aerial photographs of the same areas. > They are shoot within 15 min, the focal length, aperture stop, exposure time [quoted text clipped - 10 lines] > /Morten Nielsen > Email: http://www.iter.dk/contact.aspx What type of film ? If the color shifts are over the whole frame as opposed to part of the individual frame of each shot I would theorize- no. But since your description of the processing proceedures is so limited its very hard to track down. Since these are aerial images could it have been that they were shot through the planes plexi windows ?,... I could be angular defraction of the sunlight on the plexi as the planes position changed in such a case.  SignatureLF Website @ http://members.verizon.net/~gregoryblank "To announce that there must be no criticism of the President, or that we are to stand by the President, right or wrong, is not only unpatriotic and servile, but is morally treasonable to the American public."--Theodore Roosevelt, May 7, 1918 > What type of film ? If the color shifts are over the > whole frame as opposed to part of the individual > frame of each shot I would theorize- no. But since your > description of the processing proceedures is so > limited its very hard to track down. YUP, It's over the whole frame. It is quite easy to remove using histogram matching, but I just want know the reasons for the color-changes. I have heard that if the images isn't on the same roll of film, they can look different (can that be confirmed?). > Since these are aerial images could it have been > that they were shot through the planes plexi windows ?,... > I could be angular defraction of the sunlight on the plexi > as the planes position changed in such a case. No the imagery is done with a special (very expensive) metric camera with 230mm negative (!) Focal length is fixed to 153mm. Distortion and refraction errors in these cameras is almost non-existing (thats what makes them so expensive) The reason why I ask is that I wan't to point out the possible reasons for differences in color, as a part of my master thesis. I haven't really been able to find anything on the web about what can go wrong during the developing, and I was hoping that some of the genius' here could tell me about some of them. Btw, the negative is scanned directly to a digital image later on, so it doesn't happen when developing to a positive photograph. > I have some aerial photographs of the same areas. > They are shoot within 15 min, the focal length, aperture stop, exposure time [quoted text clipped - 6 lines] > > Any suggestions and ideas are appreciated. Aerial? How high up? I wonder if the uncorrect prints are blue and the yellow ones are overcorrected. If that's the case then it's the printing. Was this a good lab? Nick > Aerial? How high up? 750 meters. >I wonder if the uncorrect prints are blue and the > yellow ones are overcorrected. If that's the case then it's the printing. > Was this a good lab? I would think so. It's not a normal Walmart lab, since its 230mm film. /Morten >> Aerial? How high up? > 750 meters. 2500 feet. I can't find my chart with the little notes on how high the colour temp gets with altitude but assuming you didn't filter to correct then the stuff should be blue. I think that's right. It sounds to me that your scanner software is getting confused and trying to correct that blue. I think you said in a different post the stuff is getting scanned. Of course I'm assuming aerial film is set for the same "daylight" normal film is set for. Nick > 2500 feet. I can't find my chart with the little notes on how high the > colour temp gets with altitude but assuming you didn't filter to correct > then the stuff should be blue. I think that's right. I'm told that there is normally a (yellow?) filter on the lens to prevent this. Furthermore there is a filter that darkens the center of the image, since this tends to be brighter (due to the shorter distance). It seems from what people tells mere here that the most likely color errors occur during the scanning. Thanks a bunch to everyone who contributed. /Morten The color is adjusted whenever a print is made from a negative. Try getting new prints made from the same negatives, and see if the same color problem is still present. > I have some aerial photographs of the same areas. > They are shoot within 15 min, the focal length, aperture stop, exposure time [quoted text clipped - 10 lines] > /Morten Nielsen > Email: http://www.iter.dk/contact.aspx > The color is adjusted whenever a print is made from a negative. Try getting > new prints made from the same negatives, and see if the same color problem > is still present. So what you mean is that when scanning the negative, the scanning can be the source of it? I would think that the scanning is always done under the exact same controlled conditions. /Morten > > The color is adjusted whenever a print is made from a negative. Try > getting [quoted text clipped - 6 lines] > > /Morten My thought now is along the same line as Michael Covington's that the issue may be a result of the scan operator or that the scanning system is somehow at fault. There are two additional considerations, they are storage and the emulsion itself. a) The emulsion could be defective,....IMOP the less likely but it could be unevenly coated for what ever reason. b) Storage; if the film is cold stored and thawed, my opinion is that the film could produce uneven areas color areas as a result of uneven temperature while in storage, like one side of the canister or magazine faces the coldest side of the freezer, like wise in warmer conditions, sitting on the pavement waiting to be loaded and all the while picking up temperature on the sunny side. How old is the film? Have you noticed any kind of pattern? In other words are the miscolored framed evenly spaced....like every 6", 12" etc. To me that would indicate what I said above in item (b). SignatureThe joy of a forever Unknown Artist is the mystery and potential of a Blank canvas. This is a provision for the mind's eye. >b) Storage; if the film is cold stored and thawed, my opinion is that the >film [quoted text clipped - 10 lines] >are the miscolored framed evenly spaced....like every 6", 12" etc. >To me that would indicate what I said above in item (b). Hi He has a point although I am not sure it temp issue. I worked on the U-2 program and at least 25% of the missions were in color. Safe light fog is a big issue. Many of these aerial cameras are hard to load in total darkness. An IR source with a viewer is used. It's also used in processing. If it's too long, a red or reddish fog could get all over the negatives. Alot of times it will have waves in it as you discribe. Larry > Hi > [quoted text clipped - 7 lines] > > Larry I was going to include fogging but decided against it because I would have put it at the development stage. Yours is a very possible, possibilty. SignatureLF Website @ http://members.verizon.net/~gregoryblank "To announce that there must be no criticism of the President, or that we are to stand by the President, right or wrong, is not only unpatriotic and servile, but is morally treasonable to the American public."--Theodore Roosevelt, May 7, 1918 |
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