Scanning bleach-skipped film, and exposure/development advice

[ciaran_mcmenemy]

<p>This post is about scanning C41 colour film that has had the bleach omitted. If you have tried before, or have tried scanning the resulting negatives, then it would be great to hear from you. Any other advice is also appreciated, if you are sure of what you're saying!<br /><br />I used up a roll, ISO 400, with the camera set to 800 ISO, for one level of underexposure. Dyes <em>and s</em>ilver would make the negative dense, so I tried this. I developed it as normal and gave it a good wash, then fixed, washed, and stabilised it. I thought the negatives were okay because I could see all the detail when I hold it up to a light source. <br />I decided to bleach skip another roll of film. Since it was shot at the speed of the film, I developed it for 30 sec less. Same procedure afterwards. <br /> However, now that I am scanning (Epson V550) the scanner is having a lot of trouble. It can't recognise the film - it shows up as pale blue and white. I have tried three methods to get an image:<br />1) Scan as negative, adjust histogram. It works, but the scan is so noisy. Lots of coloured bits on the photo.<br />2) Scan as positive, adjust brightness, remove orange mask, invert on mspaint. This gave the best result, though it's still far from perfect. After the first attempt, it was a bit bright. I put the brightness up all the way on the scan so that the mspaint inversion would appear darker.<br />3) Scan as positive and edit with some program. I don't really know what I should do here, and the results show it.<br /><br />Do you have any advice on how to retrieve images from the negatives? There must be something I'm missing.<br /><br /><br />Advice on exposing and developing is definitely helpful as well. The best way would be to expose in a way that it can be developed normally and look 'normal'compared to other negatives. I tried one stop underexposure. Perhaps I should try two or even three stops less (e.g. 100 as 400 or 800). As for development, is it linear with time? So that, say, developing for 2:00 instead of 4:00 would give half the density? Another option is to add a weak solution of B&W developer after the colour developer and bleach steps, but then it's question of having separate bleach, which I don't (damn blix..!).</p>

[Alan Marcus]

<p>You are fighting what is called a Carey-Lea Filter. This is a layer under the top blue sensitive emulsion. This layer consists of colloidal silver. This is a suspension of super tiny particles of metallic silver in gelatin. The size of the silver particles is adjusted to cause this layer to appear yellow. This forms a blue blocking filter that prevents any of the blue exposing light to reach the underlying green and red sensitive emulsion. The Carey-Lea Filter is used in all modern color films both positive and negative. <br>

<br>

The Carey-Lea filter layer is intended to be bleached and fixed. These steps completely remove the Carey-Lea filter. Normally color films contain little if any silver. Retained silver will likely interfere with scanner operations.<br>

<br>

The Carey-Lea filter layer is not the orange mask of the C-41 process. The dyes used in C-41 film should be transparent until developed. This would be so in an ideal world. Facts are: the cyan and magenta dye are intentionally reddish and yellowish in their unprocessed state. As the film develops, the cyan, magenta and yellow dyes are chemically completed and they blossom into a full blown dye. However the cyan and the magenta dye are poor. The cyan dye should block red light and the magenta dye should block green light. This is because they are slightly off shade. No one has figured how to make them with correct color. <br>

<br>

The workaround is to tint the cyan and magenta so that two positive images are superposed on the three negative images. The mask is practically not present in high density areas and robust yellow in low and non-exposed area. The reason is, to simplify the process, the cyan, magenta, and yellow dyes are leuco (Greek for white or light). They are all missing an ingredient that causes them to blossom. In the modern color film process there is just one missing ingredient; it is in the color developer. It is super-duper difficult to get all three to have an identical missing ingredient and then blossom to the correct shade. Thus the yellow mask to the rescue. </p>

[larrydressler]

<p>Also make sure you have Digital ICE off. The silver left in the emulsion is acting just like if you were scanning B&W film.</p>

[glen_h]

<p>Even without the Carey-Lea filter, I believe it would be very difficult to scan. In addition to each dye, there is a proportional amount of silver, absorbing all wavelengths.</p>

<p>Maybe with a matrix more complicated that usual scanning software uses. </p>

<p>The mask corrects for the absorption of the cyan and magenta dyes. The difference between the absorption of the dye and the residual dye coupler has the desired absorption spectrum. It is, in general, easier to make dyes that absorb at higher energies (shorter wavelengths) than the other way around. </p>

<p>But you should be able to still bleach, fix, and stabilize and get a fine color image.</p>

[ciaran_mcmenemy]

<p>thanks for your replies. And especially for explaining the mask; I was wondering why (or rather, how) positive film doesn't have it. Is is true that negative gives better colour reproduction? Seems a bit strange to me, since slide is 'professional' film and meant for projection, and the colours don't need to be interpreted. <br /><br />Also thanks for explaining about the filter. I had no idea. It's quite smart to use silver as a filter. How they invented this stuff, I don't know....<br>

::: Are you saying it's possible to bleach-fix and image that has already been stabilised and had the silver retained??? I didn't know anything about that. Maybe I can try bleach-fixing it just until the density is good. Since I underdeveloped it, if I bleach fix it completely I think the negative will be lacking in colour and detail. <br /><br />This site here has successful bleach-skip photos, take a look https://keefmarshall.wordpress.com/2012/04/13/bleach-bypass-processing/ although they did use Photoshop, and I don't want to buy it</p>

[larrydressler]

<p>You don't have to buy Photoshop. Get a copy of Gimp. <br>

http://www.gimp.org/downloads/</p>

[Alan Marcus]

<p>The negative / positive system is best if your objective is a faithful image. Keep in mind that if we could make the truly faithful image, you would need sunglasses when viewing a sunny beach picture. The negative/positive process is most forgiving because the negative is just a means to an end. We print the negative which is actually a retake. During this retake we are allowed to make adjustments to correct errors that occurred with camera exposure, and we can make enhancements.</p>

<p>The color slide and the movies are viewed in a darkened theater etc. Thus no memory colors are available to make a comparison with. The print is viewed in full room light, surrounded by memory colors. Nobody complains much if Aunt Sally’s dress is off color so long as the face appears lifelike. The hardest to please is the artist who want a faithful photo of his masterpiece in oils. He sold his prize and wants an accurate memento. I think the best slide material was Kodachrome II. The Kodachrome process sported three color developers; this allowed for superior dyes.</p>

<p>Both the E-6 (slide process) and the C-41 (negative process) depend on silver to harvest the images. The silver is in all image layers plus in the yellow filter layer. It is necessary to completely remove this sliver, otherwise it veils the colors. The bleach step chemically converts metallic silver to a silver salt. The fixer that follows dissolves away the silver. In this way, the silver is ousted.</p>

<p> It is possible to re-bleach and re-fix after the fact. Such an arrangement is used to rescue misprocessed films. Bleach-fix or Blix is an abbreviated method. This combination shortens the color paper developing process and has found its way into film processing. Color paper is more robust and better tolerates aggressive chemicals. Color negative films that have been processed as black & white can be salvaged by re-bleaching and then putting them through, from start to finish, the C-41 process. The results are substandard but a color image is obtained.</p>

<p>The chain of events to make beautiful black & white and color photographs started in the 5^th century BCE with Mo TI a Chinese philosopher who traced with pencil images formed by a pin-hole camera. Artists of the renaissance used the pin-hole (camera obscura) as an artist aid. Heinrich Schulze (1678 – 1744) German physicist demonstrated that silver salts darkened when exposed to light. Thomas Wedgwood used this knowledge to blend silver salts into ceramics and make images of leaves. The first permanent images were made in 1826 by the Frenchman Joseph Niepce. His partner Louis Jacques Made Daguerre perfected the process. Today the Daguerreotype process announced January 13, 1893, remains unsurpassed as to resolution of detail. If we can see further than other men, it’s because we stand on the shoulders of giants. (Quote from Isaac Newton). </p>

[glen_h]

<p>The usual dyes have absorption at wavelengths that cause the colors to be less than optimal.<br>

There isn't much to do about it in the case of slides.<br>

In the case of negatives, though, the effect happens twice, both in the negative and print, which makes the problem worse. Fortunately in the case of negatives you can use masking.</p>

<p>When you scan them, you can use a correction matrix, where you adjust the image for each color layer by an amount that depends on the other layers. The result is, in mathematical terms, a matrix multiplication. </p>

[ciaran_mcmenemy]

<p>I worked out one method for scanning bleach-skipped film, and will attach some examples here. As Glen kindly mentioned that they can be blixed again (I shoulda realised that..!) some of the film is sitting in solution, so it will become 'normal' (though perhaps it will look underdeveloped. Even though I underdeveloped it, it was still dense).<br>

For anyone who's interested in this (and knows less than even me!), a scannable, 'good' density will mean you can make out the frames without having to shine a light under the negative to see them. I thought the negatives were OK as I could see them under a light, but that's too dense. The scanner struggles, and interprets it as pure white with possible light blue parts. <br>

Adjusting the main histogram so that the low (L) {shadows}, mid (M) {mid tones}, and high (H) {highlights} markers fall within the single (yes! only one) peak on the graph provides a really distorted image. A very strange sorta pixellated mess. There's a better way. Using Epson scan software (mine is V550 .):<br>

-scan as negative<br />-on the main view (not thumbnails) draw boxes where all the frames are expected to be<br />- The tone curve should not be linear, it should be curving inward (to the bottom), like a bowl. That will bring out a lot more of the light blue. Keep in in mind that the film I used is Jessops SHR400, yours may have different colour characteristics, meaning you will adjust it a bit differently. <br />- Blue histogram: bring H down until the image turns yellow or greenish.<br />- Green histogram: bring L up to reduce the green/yellow intensity. It should go towards bluey red. If still a bit too tinted, adjust blue's H slightly. <br />-Colour balance. Here you can fine tune the result. I tend to shift the green-magenta (I think that's the pairing!) towards magenta. It's all about your interpretation. Often I try to get rid of a yellow tint, without having it <em>too blue</em>.<br />-Adjusting the brightness is probably a good idea. After all, the film is super-dense and so decreasing the brightness can bring out more of the detail.</p><div></div>

[ciaran_mcmenemy]

<p>statue</p><div></div>

[ciaran_mcmenemy]

<p>red cast, I should have blued it out. Consistency is the issue with scanning bleach-skipped film. You could do a frame twice and it would look different (because of your interpretation). <br>

Central Arcade.</p>

[ciaran_mcmenemy]

<p>here's the 'distortion' I was talking about. I think it suits this sort of picture, though. Has a 'feel' to it. If you simply adjusted the main histogram and scanned that, the coloured dots (dare I call it grain?) would be much more harsh.</p>

[ciaran_mcmenemy]

<p>road and flare</p>

[ciaran_mcmenemy]

<p>university and sky</p>