Merry Christmas to all who celebrate it and happy holidays to everyone else!

I am new to Leica photography though I am not new to photography in general. This year I bought an M6 .58TTL and some lenses. I have been reading Erwin Puts Leica Compendium and admit that I am a bit confused by how best to use the knowledge provided by his lens tests. I know that leica lenses have been optimized to be sharp wide open. Most of the lenses are described as providing the best image quality at very large apetures such as f/4 or so, and then degrade somewhat if they are stopped down beyond f/8 or so. It seems to me that f/2.8 or f/4 have a very narrow depth of field. In a portrait they would show the face in sharp focus, but throw almost everything else into a blur which is probably desirable in a portrait. But what about travel and landscape photography? I am used to using wide angle lenses that are stopped down a lot in order to keep both a foreground object (or person) and background scenery in focus. With my Canon EOS gear it would not be unusual to stop down to F/11 or more in order to accomplish this. Does this lead to "degraded" image quality with Leica? Also, with available light photography using Leica lenses nearly wide open (as described by many) doesn't the extremely narrow depth of field cause a problem?

-- Steve Rosenblum (stevierose@yahoo.com), December 25, 2001

Answers

Steve: As a lens is stopped down, there are two factors affecting sharpness in the plane of focus: First, stopping down reduces the residual spherical abberation, helping to improve sharpness. So from full aperture, starting at say, f/2, things improve up to perhaps f/5.6 or so. Second, there is a phenomenon called diffraction limiting, which begins to take its toll as the lens continues to be stopped down. This has to do with the fact that light rays bend as they pass an edge. So, there is a trade-off. As we stop down, the lens is getting sharper by the reduction in sherical abberation. At the same time, it's getting less sharp because of diffraction limiting. Now, diffraction limiting is an optical law that applies internationally. It affects German lenses and Japanese ones just the same. SO, ALL LENSES LOSE RESOLUTION AS WE STOP DOWN. OTOH, there's no law against making a lens sharper, at full aperture, than the other company makes. Leica lenses are very sharp at wide apertures (not necessarily at full aperture). COnsequently, the trade-off point where diffraction limiting becomes evident can happen a stop or so wider. But at that given stop, and smaller, most Leica lenses will be just as sharp as most Canon (or other brand) lenses. I won't make this a blanket statement across the board, because I think it's best to recognize that no company has a claim on making the best lenses throughout the range. There's bound to be a lens in the Canon range that outperforms some Leica lens!

My point, though, is that there's no reason to be afraid that a Leica lens won't be as sharp as brand B, C, or D just on account of stopping it down.

-- Bob Fleischman (RFXMAIL@prodigy.net), December 25, 2001.

The fast Leica M lenses still do well at f8.0 and f11.0, just not as sharp on a test chart as at say f5.6. Real world images may even have more "percieved" sharpness at the smaller f stiops, even though total resolving capacity may go down past 5.6 or 8.0. I have tested this myself with my 90 and 50, and the resolution falls off from its 90+ LPMM peak at f5.6 and f8.0 to maybe 70LPMM at f11 and a bit lower at f16. I'd avoid f16 on ANY f1.4 or f2.0 lens unless the depth of field is the most important part of the picture. Now some of the SLR superzoom lenses on the market today actuallty have maximum sharpness at f11 and f16, so there is no hard and fast rule.

Learning to take wide open images that have "impact" can take some getting used to-and some practice at nailing the limited focus point. I am still surprised when I get these type of shots back, and sometimes the effect is what I hoped for, sometimes not.

-- Andrew Schank (aschank@flash.net), December 25, 2001.

Steve, the short and pragmatic answer to your concerns is "don't worry about it." Use the aperture that will give you the DOF that's most appropriate for the photo and let the resolution numbers fall where they may.

"Also, with available light photography using Leica lenses nearly wide open (as described by many) doesn't the extremely narrow depth of field cause a problem?"

I prefer to think of it as a solution. Happy holidays!

-- Mike Dixon (mike@mikedixonphotography.com), December 25, 2001.

Steve

Well it's a pretty complicated issue you raise. First of all, when you are hand-holding a Leica (or any other camera), the shutter speed is also important. And though you may not see any difference at low magnifications, at high mag a higher shutter speed will give a sharper image even though you can't see a difference in a 5X7 inch print. Thus, for a 35 mm Leica lens, 1/60 sec (or even 1/30 sec) will give an acceptably sharp image, but not as good as 1/125 or 1/250 sec shutter speed.

If you are into landscape photography with wide angle lenses, the apertures of f4-5.6 usually give the best results. If you set the lens at the hyperfocal distance and there is nothing of great importance in the immediate foreground (first 4-5 feet or so), you will get a clearly sharper and more pleasing image than at f8-11 with its greater depth of field.

There are some lenses designed for maximum performance wide open, so you stop down only to improve depth of field. These include some apochromatic lenses such as the Leica 100/2.8 apo-macro-Elmarit-R. The 135/4.0 Tele-Elmar already performs optically at f/4.0 in the distant range, though stopping down helps in the near range (< 2 m).

Finally, though stopping down does improve the performance of most lenses, a better corrected lens (such as the newer Leica ASPH lenses) will still perform better at smaller apertures where diffraction is becoming a limiting factor. That's because residual aberrations still contribute to unsharpness at smaller apertures. It is simply not the case that Leica lenses are only better than the competition at large aperture. And of course not every Leica lens is better than every comparable lens by Canon, Nikon, et al. This would depend upon the particular lens design, manufacturing tolerances, etc.

-- Eliot (erosen@lij.edu), December 25, 2001.

If I'm reading the core question correctly, the answer is simple: no, Leica lenses don't act any differently than others. Whatever you do with your Canon lenses works just the same with the Leica ones.

-- Michael Darnton (mdarnton@hotmail.com), December 26, 2001.

I do primarily travel/scenic photography, not portraits or street photos. IMO the so-called advantage of Leica optics IMO is mostly nullified from mid-aperture on down but I use the M because of its compactness. Additionally, more often than I'd wish for, I do end up shooting hand-held and in those cases using wider apertures to gain faster shutter speeds is paramount and it is there that Leica lenses do have an advantage, plus the lack of mirror and automatic diaphragm also contributes to less vibration. For many scenic uses, and especially with wideangles, using f/4-5.6 does not penalize DOF to that great a degree, unless you're composing with extremely close foreground objects.

-- Jay (infinitydt@aol.com), December 26, 2001.