Fuji green-cast problem solved
A couple of months ago I pleaded and begged for a solution to a problem I was having with 35mm Fuji negative film (Super G +). Many tried, but no one succeeded in exposing my ignorance. I had bought a dozen 100 foot rolls from Freestyle Photo years ago (expired 6/1998!!) and kept it in the freezer. To this day this film has absolutely no fog and, despite its rating of ISO 100, I find it a stop faster.
But...I had been having an extremely frustrating problem with its base density (outside the picture area) and, for a time, had been experiencing an ugly green cast. I tried everything, including a minute amount of potassium bromide because I thought that the 'starter' was so necessary. Sometimes victory, sometimes more of the same. I have been doing B&W since I was 14 (1964) and color since I was 28. I was fit to be tied.
I never have used a safelight in any darkroom procedure. When it comes to light fog, I am very conservative. But, also, sometimes very stupid. I have a small electric clock with a lighted dial and sweep second hand. I had put black masking tape over the front and carved a thin circle within this tape mask so that I could see the second hand and measure time in the dark. What I did not realize is the fact the color materials are hyper-sensitive to low amount of light. So sensitive that in all my years of experience I did not even think that that light was causing the problem. It was.
In the dark, after, say, ten minutes for the eyes to become accustomed to the dark, you can barely see the white of a piece of white paper in front of you. THAT, apparently, is enough to fog color film. I repeatedly verified by exposing film in the camera that had been 'exposed' to this 'darkness' for a few minutes with film from the same 100 ft roll that had not. TIme and again, the result was the same: the removed film in the first case had, indeed, been 'exposed' sufficiently to render the orange base green. The 'virgin' film from the same reel remained perfect.
To the best of my knowledge the orange base becomes 'removed' at the slightest exposure and takes on the opposite color of the light exposing it. In other words, it does not stay there and simply layer another color from the exposure (that would cause too much density to accummulate). Even though color film is no faster than B&W (traditional) film the threshold for fog is tremendously lower for the color film. Many reading this do not know that and I really was not congnizant of that to the extent that I should have been. For now on (I bulk load without a loader) my loading will be in truly TOTAL darkness and my reusable cassettes will also be loading the camera in, at least, near darkness. The years of dealing solely with B&W film had not prepared me for this 'amazing' discovery. - David Lyga
Last edited by David Lyga; 12-29-2011 at 05:46 PM. Click to view previous post history.
This is interesting.
I have an air cleaner on my furnace that is adjacent to my loading/processing area. There is a small green "on" light that I've taped over but Im sure if I go look after 10 minutes of my eyes adjusting it will be leaking.
I also have a CD player and that is covered and a luminous dial on my enlarging timer.
All these have made me paranoid in the past but I've never noticed anything detrimental.
Maybe some testing is in order.
haha... cast! I'm having a "cast" problem with fuji slides. Pink cast
Yes, the post was done primarily to warn those who are used to B&W only. The threshold for color neg material fooled even this ancient worker. - David Lyga
What you write is not true. There is no higher "threshold" in color material. It is not more sensitive. If it is ISO 100, it gives a comparable fog than the same light on ISO 100 BW film. There may be some sensitivity spikes if the wavelength is just right, but we are talking about something like half a stop or so and not a fundamental difference.
There is another reason that explains why you didn't notice this with BW film. Saturated colors jump to our eyes, just like neon lights jump to our eyes better in color than in B&W photos. You don't notice dark gray fog but notice green fog. Hence, you have seen the same level of fog in B&W film, but it was not that easy to notice. If the light were more neutral in color, you might not have noticed it with color film, either.
If you can barely see white items after your eye has adjusted, it's a pretty high level of lighting. It may be ok for some papers but not for film. The optical system (aperture) of a camera loses a lot of light so film has to be sensitive. If you can barely see self-luminous items (such as clock arms), the amount of light that reaches the film is small, but if you can barely see other objects in that light, then there's absolutely too much for any film, color or BW. Films must be handled in COMPLETE darkness and exceptions to this must be very carefully designed.
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First, the clock had a LIGHTED dial, not a luminous one. Second, certainly ISO 100 is ISO 100 regardless of the film. However, the threshold to 'challenge' the orange mask is very low. Perhaps you are correct that a commensurate amount of grey would be added with the traditional B&W material but I really think that with color film these are two different things: the grey in the B&W neg is actual potential 'image' density formed by the lowest possible light that can cause such image (ie, the 'toe'). But with color film, even BEFORE sufficient image forming light can impart an image there is a 'primary' threshold that 'gets rid' of the orange mask to 'make room' for actualy image forming density.
If what I say is entirely ridiculous, say do with candor. I am basing what I say upon much, much experimentation. I am not a chemist nor am I a physicist. But I do observe well and honestly. My ego is not at stake here; only dissemination of information and learning. I genuinely am curious as such a tiny amount of light has seemed to cause this. There is NOTHING that exposes faulty procedure like color film. Period. - David Lyga
Last edited by David Lyga; 12-30-2011 at 05:41 PM. Click to view previous post history.
Well, the orange mask should be there to compensate for unwanted dye absorption, nothing else, but nothing's perfect. Orange mask + unwanted dye absorption together combined should become constant orange density. But on the other hand, the complete system is designed so that the first bit of the toe region is discarded in printing, i.e., it will become maximum black in print, so it may be possible that the mask responds differently in this area, not meant to appear in print anyway. Second, films are supposed to be processed in complete darkness so that real Dmin from film+process can be read somewhere in the film.
So maybe you are right; If this is the case, then the question is, do the prints (or properly adjusted scans for that matter) have this same cast in blacks? Or do you only see it in negs?
You see, if the mask is not working "optimally", once you compensate it out, you can actually have "negative densities" or "blacker than black" if inverted to positive, due to imperfect masking. This would be clear to eyes when looking at the negative, but would clip to black in any printing or scanning process, analog or digital. Or, to rephrase; if the mask reacts without other imaging taking place, it will create a weak positive image, so, it cannot appear in print blacks because it will be even more black. Maybe this is the case? If you use a scanner to "lock" on the Dmin, this kind of light-fogged piece might then be problematic for this calibration; then, after locking to these "blacker than black" densities, normal densities could look like colored fog. But if you print it with your normal filtration and exposure, it should look normal.
Just a thought.
SIWA: I'm a little confused with some of your post but I'll chalk that up to my own lack of knowledge.
It might come as a shock to some, but that orange mask is not a normal coupler mask. If you process color negatives in B&W chemicals you will NOT get ANY image color but you surely will get that orange mask. And if you then bleach the B&W image out completely you will NOT be able to get rid of that oranve mask, just the complete image.
But, SIWA, I thought that the first bit of the toe region was actual, nascent density at its lowest measurable level: ie, the beginning of the image where exposure had just crossed the limiting threshold. Thus, the first bit of 'toe region' is decidedly not, as you say, 'discarded in print' (black) but, hopefully, (if negative contrast is of an index at, or below, proper relationship with the paper), shows up as the darkest shadow detail, as it well should. The orange mask was no relationship with the print (it is printed through), other that making sure that the (with all films) blue-bias is kept under control and proper hues are printed. All films have this blue sensitivity as intrinsic.
What I posed was that maybe BEFORE this threshold there is a PRIOR threshold ('pre-toe') "telling" the orange mask to get out of the way! Sounds preposturous, but somehow seems valid with my experience. That's how annoying this green cast was to me!
I am a bit confused with your last paragraph (believe me, my Finnish is non-existent). Are you saying that if you get 'print black' (DMAX) with an orange mask on the negative you will print 'blacker than black' if you negate this mask? Theoretically, yes, but practically, DMAX is DMAX and although negative numbers do exist, blacker than black will not exist. Perhaps I am not quite getting what you wish to say, especially when you say that a weak positive image will result with mask reduction. As far as I can see, the mask 'reacts' (do you mean 'is removed'?) by replacing orange with green in 'preparation' for the beginning of the image to be recorded.
I do hope that I did not throw everyting into a tailspin here. - David Lyga
Yes, as you say, orange mask exists in the film before development as you can see if you B&W process the film or just clear it by fixing. The mask works by forming weak POSITIVE images to the mask in the normal color development process, so, the mask partially "bleaches" away in the developer. But, as you cannot separate the mask from the film, you shouldn't be able to see this effect, because this mask discoloration is supposed to counteract coupling dye imperfections taking place at the same time. Together they result in constant orange density: "erroneous" negative color image + positive image in mask = constant density.
But, if you look at the characteristic curves from the datasheet, they actually measure the end-product without any compensation for masking (hence, R, G and B curves are at different Y locations) and you should be able to see this "pre-toe" as you say from the curves! But you cannot see this, so there must be some kind of explanation for this discrepancy.
Thank you hrst (SIWA): I am a bit clearer on this now but, it must be redundantly said, I do not have the in-depth theoretical knowledge that you possess. - David Lyga