Processing Tmax-100 for scanning

[David Meddings]

Hi there,

I am returning to 4x5 photography after a long absence and will develop Tmax-100 sheets in small tanks with D-76/T-max fixer. I will scan my negs on an Epson 3200 flatbed scanner (capture with SilverFast as 16-bit grayscale) and then work with the images in Photoshop, printing eventually with the ultratone inkset for the Epson 2200.

I would like advice on doing some testing to determine my best exposure index and development times. I do not have access to a densitometer. The rough outlines of my plan are to make 9 exposures of the Kodak Color Separation Guide and Grey Scale (Q-13). I will make 3 exposures each at three different EI’s – say 50, 100 and 150. I will then develop each series of low, medium and high EI’s at 3 different development times, starting from some base time then adding or subtracting 30% development time. (My normal agitation pattern is 5 seconds every 30 seconds, where I lift my negative holder out tilt left, then right 45 degrees, and replace the negative holder back in the small tank).

On a different, but related, note I am interested in ensuring that my critical plane of focus really is at the ground glass, so I am interested in suggestions on what kind of other targets I should add to my test scene to evaluate this.

Back to my basic question of EI and development time testing, one of my problems is I am not sure what to look for in the resulting scans – if I understand correctly the other posts I’ve read I should be aiming for thin negatives and not care about contrast as I can add all the contrast I want in Photoshop. For me this means I should tend towards a higher EI (I used to use 65 when printing from my negs), and perhaps shorter development times. Another more specific question I have is whether I would be better advised developing longer in a 1:1 dilution of D-76, or shorter with full strength developer.

Any and all comments on a testing process/approach that will help me nail down EI and development times very gratefully appreciated.

David Meddings

Cross posted to digital black and white the print and photo.net

[Ralph Barker]

While I can't give you any advice specific to T-Max 100, David, (I personally prefer Ilford films) here are a couple of general thoughts.

The objective of "thin" negs for scanning is really a function of the relatively limited D-Max capability of most scanners, as I see it. Dense areas of a negative that would print as subtle highlight variations might not be "seen" by the scanner. But, I would suggest the objective should really be for "slightly thin" to "fairly normal" negs, where there is good detail in both shadows and highlights. I expose and process for optimal conventional printing, and seldom have a problem scanning the resulting negs on the 3200 (or, other scanners for smaller formats). Thus, I'm of the opinion that the "thin neg" objective is a little over-stressed. So-called "problem negatives" can often be dual-scanned (one scan for highlights, another for shadow detail), and then selectively merged via Layers in Photoshop.

As to the issue of critical accuracy of your plane of focus, I'd suggest two things. First, a yard stick or similar measuring device that is held at a moderate angle from horizontal (so you can see the markings in the image), and extending both in front of and behind the point of critical focus. Second, some sort of detailed pattern that extends to the corners of the image, but is on the same plane as the point of critical focus. Prior to shooting, align everything carefully - that is, make sure the target is plumb and square to the camera, and that the camera back is plumb, too. That should show any deviation in GG placement, as well as any alignment problem (warpage) of the camera body.

[Donal Taylor]

"The objective of "thin" negs for scanning is really a function of the relatively limited D-Max capability of most scanners, as I see it."

Most of the current crop of flatbed scanners that will scan 4x5 negs/transparencies should have not problem with the density range of negative film, even if their density range figures are exaggerated byt he manufacturer. There is almost always enogugh range to get everything fromt he negative (positive/trnasparency film is another matter)

DRange... The "d" means density (and has nothing to do with dynamic range), and when measuring density that film records (as in contains valid image data), there is a minimum value (dMin), and a maximum value (dMax). The range between these two density points it the density "range", or dRange.

Positive film has a clear base...so the dMin for it is going to be quite low...as compared to negative film, which has a cloudy base...so the dMin for negative film will be quite a bit higher than positive film. Both films will pretty much have the same max density, black is still black, whether it's positive or negative film.

Well, let's say the dMax (blackest part) of both films can be measured at 3.6...and the positive films dMin is .2, and the negative films dMin is .8... That gives a dRange for the positive film of 3.6 - .2 or 3.4, and for the positive film 3.6 - .8 or 2.8.

It's purely the film base "offset" that creates the difference in density range.

Almost all the current scanners have a realsitic dRange of at least around 3.00 to 3.4 and can capture the full range of a negative.

For another discussion ...let's say that the same range of image tonality could be recorded on either film...just that negative film would have the range compressed, film density wise that is, compared to positive film. Also, the "dynamic range" of the film is not the same as the density range...and the term dynamic range is often misused when talking about density range.

[David Meddings]

Thanks Ralph and Mark,

Those are helpful thoughts and suggestions.

Ralph, your idea of keeping everything plumb is good but means I would likely shoot the scene indoors, with our standard indoor lighting. Would this influence interpretation of my EI and development time findings given that my photography uses daylight as illumination (I shoot almost entirely black and white landscapes). I realise I can shoot close to a window and not use additional lighting, but convenience being what it is and wanting to get one more shot at 11 pm etc. makes me think being able to use our standard house lighting would be convenient - still, I'll shoot the scene outdoors in daylight if the ultimate interpretation of my results are affected.

Thanks again,

David M.