Resolution and Light: Is There A Correlation?

[Snapshot]

Hi All,

I've been experimenting with some developers and I'm finding that at lower light levels, the resolution of my shoots seems to decrease. I'm thinking that at lower shutter speeds (from 1/4 seconds to 1/10 seconds) camera shake from the SLR will decrease obtainable resolution, even if mounted on a tripod. However, I can't still think that I'm overlooking another factor that contributes to lower resolution at low light levels.

Any thoughts?

 

[Jon Shiu]

Hi, also the aperture and the quality of the light (direction, hardness etc) and tone separation in shadow vs. midtone.

Jon

 

[Snapshot]

Hi, also the aperture and the quality of the light (direction, hardness etc) and tone separation in shadow vs. midtone.

Jon

I've tried to keep the aperture constant as to remove that factor from the resolution equation. I can imagine that indoor lighting and outdoor sunlight would give differing results, assuming similar intensities.

 

[Dan Henderson]

are you locking the mirror up before tripping the shutter to eliminate mirror slap as a source of vibration that may be reducing resolution?

 

[Snapshot]

are you locking the mirror up before tripping the shutter to eliminate mirror slap as a source of vibration that may be reducing resolution?

No mirror lock up. Nikon claims it's not necessary for the F100 :rolleyes: and didn't include it as a feature. However, I put a been bag on the camera. I do realize, nonetheless, that this is a source of resolution loss.

 

[keithwms]

It's true that the F100 has good mirror damping, but still, MLU does make a difference when you are talking about ultimate resolution and you're comparing shots taken on tripod. The F100 body is quite light (compared to the F5, for example) so it may well be vibrating on that timescale.

Try a heavier body with MLU, and you'll get better results. Otherwise you'll need to imrpove your coupling between the camera and a heavy tripod.

 

[lenny]

What film?

 

[Sparky]

could also be that at lower light levels - the scenes you've been shooting have had a lower SBR (contrast) and you perceive it as a lower general level of detail or 'sharpness'.

 

[Snapshot]

What film?

APX 100 shot at various EI values.

 

[GraemeMitchell]

Sharpness will also decrease if any light is hitting the lens. Used to think it was just contrast, but sharpness too as far as my experience goes.

 

[JBrunner]

Try your test with a very wide lens. If the sharpness goes back up, you will know it was the mirror.

 

[dancqu]

No mirror lock up.

Sure about that? My OM2000 does not
have MLU as such. It does have a self timer.
When activated the mirror immediately
locks up. Dan

 

[Snapshot]

Sure about that? My OM2000 does not
have MLU as such. It does have a self timer.
When activated the mirror immediately
locks up. Dan

The F100 does not have this 'virtual' lock-up feature, much to my consternation.

 

[Keith Tapscott.]

Hi All,

I've been experimenting with some developers and I'm finding that at lower light levels, the resolution of my shoots seems to decrease. I'm thinking that at lower shutter speeds (from 1/4 seconds to 1/10 seconds) camera shake from the SLR will decrease obtainable resolution, even if mounted on a tripod. However, I can't still think that I'm overlooking another factor that contributes to lower resolution at low light levels.
Any thoughts?

Reciprocity Law Failure can be a very significant factor with exposures longer than half a second or more depending on which film you are using, check out the technical data for the film you are using from the film manufacturer.

 

[keithwms]

Why not post some crops from your experiments and then we might be able to see what the issue is.

 

[panastasia]

Reciprocity Law Failure can be a very significant factor with exposures longer than half a second or more depending on which film you are using, check out the technical data for the film you are using from the film manufacturer.

Reciprocity failure pertains to exposure and contrast. Longer exposures would give vibrations time to diminish - allowing a greater part of the exposure to be free of camera shake.

I agree with the suggestion made by JBrunner, try a different lens (shorter focul length).

 

[Snapshot]

Thanks for the advice everyone. I'll give them a try this weekend.

 

[lenny]

single coating

I actually think its the film. I have noticed this on every film I have tested, altho' APX 100 is not one of the ones I have tried since I believe it is not available in sheets anymore.

All the sheet film I have tested has been based on thin coatings. I wish I knew more about the exact technology, but the truth is that it isn't the film of yesteryear. Many here will proclaim its just as good or better. It is sharp, just as a underexposed chrome is sharper, but you may not like the color balance. I don't like the midtone separation. I've talked to a lot of respected experts about this and they confirm it - even tho' many of them can't do it publicly.

I wish someone would make a premium film, that had multiple coatings of silver. Then I think you would find that it holds up. John Minakais was threatening to do this and if he doesn't have the capacity to anymore, a group of others should take up where he left off and make some film that those of us who love midtone separation (and exposure can use.

I did ask Ilford if they would consider doing this - and they didn't think there was a market. Personally, I think there are a lot of folks doing traditional things as well as alternative processes that would really appreciate this. Despite our disposable world, Photographer's Formulary seems to be doing quite well (at least from the outside looking in).

I think we need to start a movement.

Lenny
eigerstudios.com

 

[Roger Hicks]

I wish someone would make a premium film, that had multiple coatings of silver. . . I did ask Ilford if they would consider doing this - and they didn't think there was a market.

Perhaps because they were being polite?

Thicker coating = better sharpness? Hardly.

Crystal habit is another matter (for tonality), but that's not the question you addressed.

 

[lenny]

Perhaps because they were being polite?
Thicker coating = better sharpness? Hardly.
Crystal habit is another matter (for tonality), but that's not the question you addressed.

I don't care bout sharpness, and no, I don't equate them. (Nor did I in my post.) I am looking for midtone separation. All the films I have tested fall down in this area. The prints look like all the same tonalities of leaves, for instance, show up as the same tone, flattening out the print. Leaves aren't that consistent in tone - until they are dead anyway....

I am unfamiliar with the term crystal habit - can you elaborate?

Lenny

 

[Roger Hicks]

I don't care bout sharpness, and no, I don't equate them. (Nor did I in my post.) I am looking for midtone separation. All the films I have tested fall down in this area. The prints look like all the same tonalities of leaves, for instance, show up as the same tone, flattening out the print. Leaves aren't that consistent in tone - until they are dead anyway....

I am unfamiliar with the term crystal habit - can you elaborate?

Lenny

Dear Lenny,

Sorry to have been so rude. The original post was about resolution/sharpness. I apologize for conflating that and your reply.

'Crystal habit' is essentially crystal shape and size. Classic crystals are more or less cubic, or small pyramids.

'Tabular' crystals are big and flat. With correct exposure and development, multiple development sites on one crystal lead to more speed at a given grain size, or finer grain at the same speed, or a combination of the two, with better sharpness. Overexpose or overdevelop too much, and sharpness and grain fall off a cliff.

There are lots more tricks you can play with crystals: epitaxial growth (Ilford's 'Delta'), positive hole traps (Agfa patents) or, going into the past, gold sensitization (Agfa again). None relates that well to tonality, but that's a black art, not greatly related to silver content alone.

Tonally, my favourite films are non-monosize emulsions (old-fashioned crystals, fairly coarse-grained) such as Ilford HP5 Plus, Kodak Tri-X and Fomapan 200. But this is a separate question from 'silver rich', not least because you can stuff as much silver as you like into an emulsion without improving it at all. Once there's enough, there's enough, and adding more won't help.

For what it's worth, in papers (not films) at least one manufacturer at one time used more silver than is needed in some emulsions, to satisfy the demands of the ignorant for 'silver rich' paper.

Cheers,

Roger

 

[aldevo]

Dear Lenny,

Sorry to have been so rude. The original post was about resolution/sharpness. I apologize for conflating that and your reply.

'Crystal habit' is essentially crystal shape and size. Classic crystals are more or less cubic, or small pyramids.

'Tabular' crystals are big and flat. With correct exposure and development, multiple development sites on one crystal lead to more speed at a given grain size, or finer grain at the same speed, or a combination of the two, with better sharpness. Overexpose or overdevelop too much, and sharpness and grain fall off a cliff.

There are lots more tricks you can play with crystals: epitaxial growth (Ilford's 'Delta'), positive hole traps (Agfa patents) or, going into the past, gold sensitization (Agfa again). None relates that well to tonality, but that's a black art, not greatly related to silver content alone.

Tonally, my favourite films are non-monosize emulsions (old-fashioned crystals, fairly coarse-grained) such as Ilford HP5 Plus, Kodak Tri-X and Fomapan 200. But this is a separate question from 'silver rich', not least because you can stuff as much silver as you like into an emulsion without improving it at all. Once there's enough, there's enough, and adding more won't help.

For what it's worth, in papers (not films) at least one manufacturer at one time used more silver than is needed in some emulsions, to satisfy the demands of the ignorant for 'silver rich' paper.

Cheers,

Roger

Several years ago PhotoTechniques published an article regarding the silver actual content of papers. It was probably a bit of eye-opener for many since the variations amongst the manufacturer papers surveyed was quite small and the rankings were not what you might have expected.

To my knowledge, only Agfa has ever bothered to publish the silver content of their modern papers. They immediately acquired a reputation for being "silver-rich" having done so.

 

[gainer]

Loss of midtone separation sounds like a flare problem. I'm trying to think of a good way to isolate this possibility from the other ones. Usually it varies with lens opening, but it could be some kind of light leak around the lens that varies with exposure time. Lens flare could be tested on a bright scene at high shutter speeds and the corresponding lens openings to see if all the possible combinations gave the same midtone separation. 1/25 to 1/500 should give an idea without invoking low intensity reciprocity failure. Perhaps looking through the viewfinder with the lens capped and the shutter open would show something. A small light leak around the raised mirror might give enough flare light to flatten the slope of the characteristic curve of the film.

 

[gainer]

I shoulf have mentioned that my Canon EOS neckstrap has a cover for the eyepiece that is to be used when the eye is not, to keep light from entering there and causing fog.

 

[Dorian Gray]

Unless you're using a particularly poor tripod, or a particularly long lens, or shooting macro, I have my doubts that mirror slap is causing an appreciable lack of sharpness. I suppose it depends on the exact degree of difference in sharpness you're noticing between bright light and low light exposures. To be sure that the mirror is not causing a problem, stop down the lens to allow a shutter speed of 1 second or more, although if that requires an f-stop higher than f/11, use an appropriate ND filter (though one of good quality or it may introduce its own problems). Lenses for 35 mm cameras tend to become noticeably less sharp after f/11 or so, due to excessive diffraction.

Perhaps you're overexposing the areas of the film with the soft detail? Overexposure reduces sharpness. Of course the exposure you're using may be needed to capture the overall brightness range you want, in which case you'll just have to move up to medium-format or better. With large format in particular you can practically expose as much as you want without worrying about sharpness and grain.

Flare also reduces contrast, and therefore sharpness, and it's possible that your low-light scenes include extremely bright light sources relative to the rest of the scene, such as street lamps, which could cause flare. What lens are you using?