Film grain and sharpness Question

[brian steinberger]

I've been shooting Ilford FP4 and HP5 only for a while now, but seem to notice something strange. I process myself and print myself. I print no larger than 11x14 for the time being. I notice that my negatives shot on the HP5 "appear" sharper in the print. They're also easier to focus with the grain magnifier. I realize that this is because of the grain. But with shooting 4x5 and enlarging to only 11x14 could the grain not be a "distraction" as it is with smaller formats, but rather a "sharpener?" For example, I took a shot with alot of grasses and trees on HP5 and the print is so sharp and the detail runs and runs forever. My shots on FP4 are nice, but kind of slightly seem mushy. Fine grain films are so fine grained now. It almost makes want to exclusively shoot HP5. Is this something that every here knows and I just realized? Any comments?

[Bill_1856]

Welcome to the real world.

[Ralph Barker]

The short answer is "yes". The longer version is that I think you are seeing the effect of several trade-offs in the overall process. The characteristics of the film/developer combination will affect "apparent" sharpness. That is to say, developing for finest grain will generally reduce apparent sharpness. Thus, up to a point (enargement-wise), increased grain can actually make the image appear to be sharper, but sometimes with a loss of tonal gradation. The trick, I think, is to pick film/developer combinatios that give you what you want in the print sizes you want to make.

[Dawid]

Hi

I've seen the same trade off esp. in 35mm working with FP4+ developed in Rodinal. The prints are sharp but the grain at times distracting when enlarging to 8x10 -- grain less noticable with ID-11. However, I have been shooting 4x5 Fuji Acros for the last 3 months developed in Rodinal and it is incredibly sharp as well as very fine grained. Haven't tried the Acros in anything else yet but cannot imagine a different combination beating it.

Cheers

[Oren Grad]

Brian, that's one of the things that people have in mind when they say that each film - or, in fact, each film/developer combination - has a distinctive character or flavor to it. Some people like to develop in Rodinal, for example, specifically to enhance the subjective appearance of sharpness or "edginess" by producing more sharply-defined grain.

For my taste, FP4 Plus is similar to HP5 Plus in this respect. That is, although it's certainly finer-grained and smoother than HP5 Plus, like HP5 Plus it is on the gritty/grainy end of the spectrum compared to other films in its speed class.

If you'd like to understand the range of possibility here, you might do some tests with T-Max 100. Although TMX is objectively an extremely sharp, high-resolution film - a further step up in these respects from FP4 Plus - it does tend to produce a subjective effect that many viewers perceive as soft-edged, especially if anything less than the most meticulous technique is used in enlarging.

[Bruce Watson]

Is this something that every here knows and I just realized?

Not everyone knows. But if you stay with film long enough, you are just about assured of making this discovery. It is a well known and well studied phenomena. What it is is the difference between your perception and what the film actually does. And part of this is the image processing part of your eye/brain system filling in holes in the image based on clues from the image.

In other words, sharpness isn't a well defined term. But accutance and resolution are. They don't all mean the same thing, but describe different aspects of the image. The key is local contrast. That is, the differences in value where two surfaces meet - a twig and it's shadow for example. If you make the shadow a little darker, you perceive the image to be sharper even though it isn't giving you any more information.

The bottom line is this: In practice, larger grained images often feel sharper even though they don't resolve as much physical detail as smaller grained images.

[paulr]

"In other words, sharpness isn't a well defined term. But accutance and resolution are."

they all have somewhat hazy definitions. sharpness might be the easiest, because it's a purely subjective, descriptive quality. what optical scientists do is ask test subjects questions like "on a scale of 1 to 10, how sharp does this look?" ... and then they measure dozens of attributes to try to figure out what's responsible for that impression. the qualities that are linked to it are more complex than anything that can be represented with a single number.

accutance and resolution are measureable qualities, but there's no agreed on standard for how to measure them. so one person's or lab's resolution numbers can't be compared to another's, unless you happen to know they're both using the same methodology.

this is all why MTF curves have become the most popular measure ... they're objective, and they combine several of the most important metrics into one figure.

the MTF qualities that are leading to the granier print looking sharper might be directly associated with the grain, and they might also be associated with other similar edge effects (increased contrast at the right resolutions for your print sizes). this is the Velvia trick ... if you look at the MTF curve for velvia, you can see edge effects that increase contrast beyond 100% at the lowest resolutions. so the chromes look sharper than real life on the light table. but the effect diminishes as magnification increases. by the time you blow up one of those chromes by 5X or so, its limitations become more clear ... you can start to see that it's actually a much lower resolution film than something like t-max.

this is also what you do when you use sharpening filters in photoshop. it's interesting to see what happens when you take a file that's been beautifully sharpened for a particular print size, and then print it much larger or smaller.