Speed difference between Acros II, TMX, and Delta 100 at same CI?

[miha]

If they are all developed to the same contrast index, is there any real speed difference between them?

Thanks.

 

[Andrew O'Neill]

I've shot all three at EI 80, roughly the same CI, and I couldn't see any difference. It may be measurable with a densitometre, but not with the eyeballs.

 

[MattKing]

Which speed criteria are you using - something like Zone System criteria, or something more akin to the ISO standard?
@Stephen Benskin may wish to chime in.

 

[miha]

ISO standard.

 

[retina_restoration]

No appreciable difference, no.

 

[Milpool]

No, they have the same 100 ISO speed. Where they differ is contrast in extreme highlights. This will of course vary to some extent with the developer, but generally speaking TMX and Delta 100 are very similar with a long, gradual shoulder whereas Acros (at least Acros I, I haven't used Acros II) has higher highlight contrast - ie straight line continues further with a more abrupt shoulder at the end.

Note just because you develop them to the same gradient doesn't necessarily mean you are developing to the gradient required to meet the criteria for ISO speed (roughly a gradient of 0.63). For example if you developed them all to the same, but very low gradient, you might decide they need different EIs if the curves change in different ways with extreme processing. Etc.

Edited typos.

If they are all developed to the same contrast index, is there any real speed difference between them?

Thanks.

 

[miha]

Gradient 0,63 sounds about right for my (semi)condensor Durst enlargers.

 

[DREW WILEY]

There absolutely is a difference due to the different characteristic curves approaching the toe, with respect to shadow reproduction. This comes into play in high contrast scenes. For all practical purposes, under such situations, TMax films are one full stop faster; with careful shadow metering, you can safely use them at full box speed of either 100 (TMY) or 400 (TMX). But to get similar deep shadow gradation with Delta 100, FP4, and Acros, you have to boost the shadow exposure further up the curve by cutting you film speed in half (50). Even then, you won't get quite as much shadow gradation, but will get a significant improvement.

Highlight repro is controlled by the degree of development instead; hence the old adage, "expose for the shadows, develop for the highlights".

Now a "new" vs "old" remark : For a long time now, current TMax 100 has been largely cured of the shouldering off risk at the top of the first version of that product, although you can't be careless about it. Old FP4 and current FP4 Plus behave pretty much the same in that respect, so too does current Acros II in relation to original Acros. Delta 100 seems to have stayed the same all along.

There is a minor improvement in shadow repro with the new Acros II; but the main difference from the former version is in slightly less sensitivity to blue. Otherwise, both are orthopan spectral sensitivity, not conventional panchromatic. The nice thing about Acros is that it can be developed together with FP4, so similar are they in exposure speed and curve shape. Don't try that with Delta, however. All of these particular films are less fussy than TMax, which is more of a high-performance film (and my favorite).

 

[miha]

TMX has always been my soft spot, but I’ve never shot a roll in 135!

 

[DREW WILEY]

I shoot both TMX100 and TMY400 in multiple formats : 35mm, 6x7, 6x7, 6x9, 4x5, and 8x10. I've got some 8x10 in my big camera pack right now, awaiting a break in the rain and overcast (which probably won't happen today, but tomorrow). But I'm very familiar with those other films in question on this thread too - all of them are excellent products, but not as versatile in the extreme lighting conditions I often encounter as TMax films are.

 

[miha]

I've shot some in 120, never in 4x5 - too expensive. At present i'm stocking up on slow - well, what we us to call 100 iso medium speed- 135 film for a personal project.

 

[DREW WILEY]

I bought a lot of TMax film back when it was much cheaper, and stockpiled it in my freezer. It should still be perfectly usable until I'm too old for shooting 8x10 anymore. Nowhere near as expensive as the equivalent color film, which I've got stashed away too. For some people, cost is no object. Others, like lots of 4-wheelers, will burn up a $4,000 set of tires in a single summer. Look at what people pay for tickets and hot dogs at pro sports venues. So it's just a matter of priorities. When I need to save money, I shoot 120 roll film; but I do a lot of that too simply for sake of convenience is windy conditions, or quickie walks, etc.

 

[miha]

I don’t live in the past, my two freezers contain everything but film, so I have to buy whatever is actually available.
That said, Foma 100 4x5 is more than capable of producing gorgeous 12×16 inch prints, so I’m perfectly happy working with it.
135, of course, is a different story entirely, but that’s part of the fun and the challenge.

 

[DREW WILEY]

Foma 100 has a curve structure more like that of FP4 etc. Foma 200 has an even longer straight line than Tmax, but that feature is offset by its questionable quality control, horrible reciprocity characteristics, and quite overoptimistic box speed rating. Still, it's an interesting product worth trying, and within the same affordability spectrum as other Fomapan films.

I just can't risk dicey quality control. The last time I shot Foma "200" (really a 100 speed film itself), I lugged the 8x10 way up a steep "goat path" to over 10,000 ft elevation to get a shot of a nearby higher pinnacle. The contrast range was extreme, all the way from shimmering ice in direct sun to deep pits and pockets in dark volcanic rock (plus a red filter factor). The film handled that range remarkably well; but it was hell spotting out all the little zits and emulsion cracks enlarged onto the print.
Had the same thing happen with other shots, trying two different batches of the stuff in 8x10 sheets. Never again. But nobody has complained about those symptoms on the other speeds of Fomapan.

 

[reneboehmer]

If they are all developed to the same contrast index, is there any real speed difference between them?

Thanks.

Contrast index is a measure of curve slope and in itself has no connection to the speed point. The ISO speed of the film is determined by how much exposure is needed in order to build a certain amount of density under specific geometrical conditions of the film curve, as well as acurately defined processing. The effective film speed is the point where this density is reached, without ISO conditions, in your own process. Two films developed to the same Ci will give similar resulting Density ranges, for the same scene.
You can develop a film with a speed of lets say 80 to a Ci of 0.58 and a film with a speed of 400 to a Ci of 0.58.

Ci is simply the steepness of a linear line that gets "overlaid" with two specific anchors onto the film curve.

This is the speed point, it is found there where the exposure results in curve densities crossing a certain threshold and tonal seperation starts to build. The speed is determined by reading the value on the X axis (the illuminance x time that hit the film surface).

Here is a comparison of films that have different speeds but the same Ci

Even tho, all films mentioned are advertised as ISO 100, this speed does only apply under ISO conditions, each film will most likely have a different speed point in your own process.
F.e. one might be 100, one might be 80, one might be 125. It's hard to tell without tests.

 

[Stephen Benskin]

It depends on what they are processed in. Since they are from three different manufacturers, there's a good chance there are three different developers involved, so there is no direct comparison, but the speeds are probably comparable.

 

[miha]

F.e. one might be 100, one might be 80, one might be 125. It's hard to tell without tests.

Hence, my question

 

[loccdor]

I tried T-Max 100 for the first time recently, and thought it was alright, but I saw more visible grain than with Acros, and I also prefer Acros' spectral sensitivity.

 

[reneboehmer]

Hence, my question

To know exactly you have to make sensitometric tests.
But most likely you won't notice a much of a difference under real conditions.

 

[miha]

I tried T-Max 100 for the first time recently, and thought it was alright, but I saw more visible grain than with Acros, and I also prefer Acros' spectral sensitivity.

You must have blown up the two quite a bit!

 

[DREW WILEY]

Depends on not only the specific developer, but also its amount of dilution into working solution, and hence overall development time. Generally, Acros will yield finer grain than even TMax, but under certain development conditions, it's the other way around. But frankly, for me the main problem with TMX100 is its comparative lack of crisp edge acutance, which is in fact improved by means of a little more grain growth during development. I won't go into details I have explained elsewhere already, but just point this out.

Spectral sensitivity is a different question. Acros tends to lend a more natural look with foliage. I shot a lot of it in 4x5 Quckload sheets for backpacking purposes, when that option was still around. A lovely high country film. Kodak's Readyload sleeves were more problematic, especially when they were first introduced as a two-sheet version.

Blowing them up? ... I have trouble even focussing on Acros grain, it's so darn small, despite having the very best easel grain magnifier and high end apo enlarging lenses. My most common application for Acros is enlarging 6X7 6x9 negs to 16X20 inch nominal print size. But enlargement from tiny 35mm Acros negs do sometimes show grain in the print, even though I never print 35mm anywhere near 16X20 size.

 

[Stephen Benskin]

Seasoned Xtol. Dip & Dunk. EG&G Mark VI calibrated sensitometer.

DEL 100, CI 0.61 EFS 100
TMX, CI 0.61 EFS 80

No data for Acros.

ISO parameter is Δ0.80 density above 0.10 and Δ1.30 logH from 0.10. This equals an average gradient of 0.615. CI is a different method. With a short toed curve the two methods will likely agree. With longer toed curves, from a CI perspective, the CI is higher than 0.615 in order for the film to reach the Δ0.80 density.

Diffusion enlarger Grade 2 LER ~1.05

Condenser enlager Grade 2 LER ~0.80

 

[Augustus Caesar]

If they are all developed to the same contrast index, is there any real speed difference between them?

Thanks.

Yes. The Fuji is about 50, T-Max is 100, and Delta 100 is about 80.

 

[Augustus Caesar]

Gradient 0,63 sounds about right for my (semi)condensor Durst enlargers.

HUH? For condenser, 0.43 is closer to ideal.

 

[MattKing]

Yes. The Fuji is about 50, T-Max is 100, and Delta 100 is about 80.

Sounds like a Zone System speed, not a speed determined according to ISO criteria.