I was complaining to a friend that I had a great negative that was too dense, and when printed on soft paper looks abysmal at the very best. He suggested an unsharp mask, which I have never attempted … and thanks to Ed Buffaloe’s website I’ve discovered latent image bleaching to reduce print contrast (which I have never tried either).

So the question is, do both techniques produce the same results? Or are there times when one might prefer to use one method over the other? I can definitely understand how latent image bleaching is much easier to do than unsharp masks :-)

TIA – Doug

-- Doug McFarland (junquemail222@yahoo.com), January 07, 2001

Answers

I've never done unsharp masking, but where I have seen it done it produced an overall sharpness that was almost unreal, in addition to improving gradation. The results were marvellous. So unsharp masking does more than latent image bleaching can do.

-- Ed Buffaloe (edb@unblinkingeye.com), January 07, 2001.

Ed, wouldn't a properly exposed neg give you the same thing? It seems like Davids latent image reduction is a little bit complicated and chancey. Have you tried it extensively? How do you know how much to bleach the neg before you develope it? I know that masking can easily tame an N+3 situation so would this be a better more controllable method vs latent image bleaching? More info please. Have you done it? James

-- james (james_mickelson@hotmail.com), January 08, 2001.

I certainly would not claim that latent image bleaching is a panacea, and I don't recommend it for every negative or print. It is simply another useful technique that is worth experimenting with.

Using latent image bleaching on negatives has the opposite effect from latent image bleaching on prints--it prevents blown-out high values in negatives, whereas it prevents loss of detail in shadow values with prints.

I have used latent image bleaching enough with prints that I can recommend it for very high-contrast negatives that are difficult to print. The negative has recorded the full scale of the scene (detail in shadows and high values), but the problem lies in getting the scale of the negative to fit the scale of the paper. If you print such a negative on a grade 1 or 2 paper, the print loses the brilliance that caused you to photograph the high contrast scene to begin with, so why bother? But if you print on a grade 3 or 4 paper and bleach before developing, you get detail in the low values without compromising the brilliance of the high values. I have an example of a print that was produced with this method in my article on latent image bleaching.

I have not used latent image bleaching extensively with negatives. My response to Doug's question was in regard to latent image bleaching of prints. The way to know how much to bleach before development (with negatives or prints) is through prior testing with the film or paper in question. Once you have calibrated, you can always use the same bleach time, so it isn't that difficult.

Unsharp masking has the advantage of producing remarkably sharp prints, but it is also a lot of trouble and requires considerable testing to perfect. The leading proponents of unsharp masking often use it for all their negatives, not just high-contrast ones, so they are opting for sharpness in addition to gradation.

It might be preferable to use good zone system practices to get a perfect negative to begin with, but David Kachel has some interesting critiques of traditional zone system methods of contraction. My information on latent image bleaching comes from two articles by David Kachel in Darkroom and Creative Camera Techniques magazine: “Zone System Contraction, Part III: Selective Latent Image Manipulation,” Vol. 11, No. 5, September/October, 1990 and “Variable Contrast Control From Graded B&W Papers,” Vol. 13, No. 3, May/June, 1992. Kachel states that traditional methods of negative contraction (water-bath development, reduced development time, high-dilution compensating development, and two-bath development) are "either obsolute, unwieldy, or both." "Films...simply do not respond to these techniques the way they once did." He states that with latent image bleaching you can process contracted negatives together with normal negatives using the same developing times, without producing an artificial shoulder and with a minimum of speed loss.

In the 1990 article Kachel displays a print from a 4x5 Tech Pan negative, where the negative was bleached for 5 minutes then developed for 12 minutes in HC-110B--the print, on a grade 2 paper, has normal contrast and even gradation. He claims the method produces a higher than normal film speed for Tech Pan.

-- Ed Buffaloe (edb@unblinkingeye.com), January 09, 2001.

Ed, coincidentally I had just read about latent image bleaching on your web site, then saw this. In your article, you state that paper speed will be reduced "by at least a full stop." Does this vary widely with different papers, or is a stop pretty reasonable as a place to begin? I guess if you know you're going to do it, you can just bleach test strips and all. How much dodging/burning (done purely because of too wide a contrast range) does this eliminate for you? This really sounds pretty exciting...Thanks.

-- John Sarsgard (sarsgard@yahoo.com), January 09, 2001.

In regard to John's question about paper speed when using latent image bleaching: the speed reduction may vary slightly from one paper to the next, and may be influenced by bleach dilution and bleach time. If you know you need to bleach a print, just go ahead and do the whole process on a test strip and calculate your exposure time accordingly. If dodging will do the trick, I will opt for it over latent image bleaching, because it is usually less trouble. But if the image has a dozen places that need to be dodged, or if the place is small or otherwise hard to dodge, latent image bleaching may be the only way to go. In some cases it is possible to simply do local bleaching after the print is fixed, but if there are highlight values in the middle of a dark area, they will be bleached out of proportion to the dark areas, whereas with latent image bleaching the high values are not affected at all.

-- Ed Buffaloe (edb@unblinkingeye.com), January 09, 2001.

Ed, thanks for the info on latent negative image bleaching. I will have to try it. James

-- james (james_mickelson@hotmail.com), January 09, 2001.

Someone sent me a request for the URL of my article on latent image bleaching. This is a bare-bones article, intended only to present the technical information from David Kachel's original articles in a convenient format.

http://unblinkingeye.com/Articles/LatentImageBleach/latent imagebleach.html

-- Ed Buffaloe (edb@unblinkingeye.com), January 10, 2001.