contrasty/noncontrasty lenses?

[BetterSense]

I never really noticed a difference in the contrastiness of camera lenses before, but I bought an Olympus XA and despite that I'm shooting at a lower EI (800) than I usually do when using Diafine, my negatives are needing 1-1.5 grades less contrast than they do on my SLR cameras. Could it be that the strange f/3.5 lens on the XA is a 'more contrastier' lens?

 

[brofkand]

I am not familiar with that particular lens, but it could be you're slightly over or underexposing your negatives on your SLRs, that could cause a loss in contrast. Lens flare causes loss of contrast. And yes, lens coatings/designs/accuracy causes losses (or gains) in contrast. A Holga lens is less contrasty than a Nikkor 50mm 1.8 for example, ceteris paribus.

The most probable answer (outside of lens flare) is over or underexposing your negatives. Incorrect exposure either way will yield a less contrasty print.

 

[keithwms]

Yes, why not bracket a roll and see if the exposure is the reason. Anyway, you're not using an XA, right? It's an XA2 or similar? If so then you are probably (auto)metering quite differently than you might on an SLR or the original XA.

I don't recall seeing especially high contrast from the XA or XA2 cameras that I've used. Could be that the XA2 lens is a bit contrastier but even so I doubt it'd have that much effect on contrast grade. Probably an exposure issue.

 

[phenix]

Contrast in lenses might make huge differences, depending on the subject you shot (ex: landscape or portraits). It is accurately measured by the MTF graphs. Unlikely to film, the MTF curves are measured differently (at 3-4 resolution values across the lens radium, not on a continuous resolution scale). You also have multiple grafs for multiple aperture values.

To learn if a lens is more contrasty than another for a specific aperture, you should look at the distance between the 100% line and the first MTF curve, than at the distances between this first MTF curve an the rest of them. If all MTF curves are grouped close to the 100% line, than you have a high contrast lens. If only the first curve is close to the 100% line, than the distances between curves is gradually increasing, you are on the low contrast side. Finally, if even the first MTF curve is far from the 100% line, you either have a bad lens or the wrong aperture. Because looking at the graphs for different apertures, you’ll also learn at what values your lens works at its best.

You should also look for the fall-of of each MTF curve (the center of the lens is at left, and the margin at the right of each curve). This fall-of might be undesirable for landscapes, while being suited for portraiture.

Check this site for some examples and further explanations: http://www.photodo.com/

 

[BetterSense]

I have an XA2. I set the dial on 800. The thing that confuses me, is this is MORE exposure than I usually give on my SLR cameras when I shoot at 1250. It looks like the negatives are at least as dense, too. Giving more exposure is supposed to decrease the contrast of the negatives.

So even though by the numbers I'm giving more exposure, the negatives are still coming out contrastier. I usually print my diafine-developed negatives at grade two or three, but tonight I had to print at grade 1, and then I started falling back to split-grade printing where I was giving rather short high-contrast exposures (14s at 00, 5s at 5). Typically I end up with comparable times for the 00 and 5 exposures.

It could be the developer is migrating or something, too.

 

[abstraxion]

http://www.flickr.com/groups/olympusxa/pool/ - You tell me.

I've found that XA images tend to look contrasty, and the images in this flickr pool tend to support that assumption in my opinion. People often talk about the XA/XA2 in the same sentence as the LOMO LC-A since they both have very contrasty lenses.

 

[Anon Ymous]

I have an XA2. I set the dial on 800. The thing that confuses me, is this is MORE exposure than I usually give on my SLR cameras when I shoot at 1250. It looks like the negatives are at least as dense, too. Giving more exposure is supposed to decrease the contrast of the negatives.

But you'll need to decrease development time. It seems that you overdevelop your negatives, resulting in high contrast.

 

[BetterSense]

Diafine has a fixed development time. I can't adjust development; there is no overdeveloping.

The only way to adjust contrast with Diafine is to change exposure, and less exposure results in more contrast, more exposure results in less contrast. I think I'm going to try pushing to 800 with conventional developers in this camera.

 

[c6h6o3]

To learn if a lens is more contrasty than another for a specific aperture, you should look at the distance between the 100% line and the first MTF curve, than at the distances between this first MTF curve an the rest of them. If all MTF curves are grouped close to the 100% line, than you have a high contrast lens. If only the first curve is close to the 100% line, than the distances between curves is gradually increasing, you are on the low contrast side. Finally, if even the first MTF curve is far from the 100% line, you either have a bad lens or the wrong aperture. Because looking at the graphs for different apertures, you’ll also learn at what values your lens works at its best.

I simply loaded a roll of film into my Hasselblad, made six exposures with the 80mm Planar, then changed to the 150mm Sonnar lens and shot the rest of the roll at the same aperture.

The Planar negatives are about 1 contrast grade more dense in the highlights than the Sonnar ones. I know that this is not overall density I'm seeing because the shadow density is the same for all the negatives.

So, to answer the question: Yes, some glass is more contrasty than others, even from the same manufacturer-Zeiss in my case.

 

[psvensson]

Diafine has a fixed development time. I can't adjust development; there is no overdeveloping.

Diafine produces excessive contrast with many films, so you could consider it as overdeveloping compared to a conventional developer.

 

[dynachrome]

If your film is exposed properly, Diafine will not cause excessive contrast. The effect on speed of using Diafine is different with each film. In general Diafine produces less contrasty negatives. That's why it's preferred for contrasty lighting. When the Olympus OM system came out, several camera magazines described the Zuiko lenses as having unremarkabe resolution but very high contrast. Even the famous 50/2 Dual Range Summicron, which has very high resolution, is considered to be low in contrast by today's standards.

 

[phenix]

...When the Olympus OM system came out, several camera magazines described the Zuiko lenses as having unremarkabe resolution but very high contrast. Even the famous 50/2 Dual Range Summicron, which has very high resolution, is considered to be low in contrast by today's standards.

When contrast (or acutance) increases, resolution falls. The reverse is not always valid.

The explanation is simple: increase in contrast means fewer grays. Or, at higher resolutions, even the blackest black and the whitest white show up as very close gray tones, that a high contrast glass or film will not be able to see and record. Contrast (or acutance) means constant-high visibility at lower and middle resolution values, after which this visibility drops abruptly.

Now the reverse: having a low contrast glass doesn’t necessarily mean that it allows high resolution. It simply can be a bad piece of glass. But if it’s a good one, it should do high resolution.

 

[Q.G.]

When contrast (or acutance) increases, resolution falls. The reverse is not always valid.

The explanation is simple: increase in contrast means fewer grays. Or, at higher resolutions, even the blackest black and the whitest white show up as very close gray tones, that a high contrast glass or film will not be able to see and record. Contrast (or acutance) means constant-high visibility at lower and middle resolution values, after which this visibility drops abruptly.

Now the reverse: having a low contrast glass doesn’t necessarily mean that it allows high resolution. It simply can be a bad piece of glass. But if it’s a good one, it should do high resolution.

I don't agree.

Increase in contrast means that light is spread less over areas it shouldn't be in.
At higher resolutions, even the blackest black and the whitest white will still be the blackest black and the whitest white.
That increases resolution.

Increase in contrast does not mean fewer grays. Only fewer false greys. Less, or no, veil over areas that should be black.

Such a veil (that is producing the low contrast in low contrast lenses) is produced by light that should be in highlight areas, so they are reduced in intensity - become more grey - too.

Grey tones are still rendered as grey tones. No light is added nor taken away.


Low contrast lenses do spread light over areas it should not be in.
The veil drowns fine detail, fills troughs between highlight detail, and fills dark detail.
That does not necessarily make them disappear, but will make them less apparent (which is why MTF, a function of contrast against detail size/frequency is used as a measure for lens performance, not resolution or contrast alone).

While high contrast does not mean fewer greys, low contrast does mean fewer blacks (and whites).

So "When contrast (or acutance) increases, resolution" increases as well.

 

[David A. Goldfarb]

Keithwms is probably right.

The XA2 has a tessar type lens--not "strange" at all, but the most popular lens design in the history of photography--which should be fairly contrasty. I haven't owned an XA series camera myself, but hunting around for comments there is some sentiment that the XA2 tessar-type seems sharper than the fancier 6-element XA lens, which isn't surprising. With the same coatings, a tessar will often look contrastier than a plasmat or planar type, but it won't be as sharp in the corners. For some kinds of photography (standard types of portraiture, for example), sharp in the center and soft in the corners is just fine.

Also, you can't really compare EI 800 on an XA2 to EI1250 on your SLR, unless you know that the shutters are both accurate--and even then, it's hard to say what that means when the XA2 has a leaf shutter and the SLR has a focal plane shutter--and the meters would have to work in the same way, which they don't. Beyond being within a stop of each other, I wouldn't really expect to be able to make the kind of critical comparison you're making here.

You don't mention what film you're using, but it is likely that by giving more exposure on the XA2, you're pushing the image to a steeper part of the curve, and that is giving you more contrast. Put another way, maybe at 1250, more of the shadows are resting on the toe of the film's characteristic curve, so the highlights aren't very high up on the curve, and if you exposed at 800, you would get more tonal separation throughout the tonal range.

 

[BetterSense]

You don't mention what film you're using, but it is likely that by giving more exposure on the XA2, you're pushing the image to a steeper part of the curve, and that is giving you more contrast. Put another way, maybe at 1250, more of the shadows are resting on the toe of the film's characteristic curve, so the highlights aren't very high up on the curve, and if you exposed at 800, you would get more tonal separation throughout the tonal range.

This makes sense.

I'm using Tri-X, which pushes pretty well with Diafine. The last couple half-rolls I've tried pushing with D-23 hoping to get finer grain with a developer that I can control contrast with. But there's seems to be less shadow speed with the conventional developer and the grain isn't much different. I always wondered if Diafine actually increased 'real' speed or just seemed like it because it was such a low-contrast compensating developer that protects the highlights and thus doesn't 'look pushed'. I haven't done any formal tests but I think it actually does give a little bit more speed.