How sharp does a lens have to be ?

The answer to the question is that it all depends.

My holiday snaps end up on 5x7's and it really doesn't matter. But if was doing a talk and needed slides for a screen 12ft high by 18ft I might not get away with it using the P&S and would have to get out the Leica/Olympus/Minolta and tripod etc.

And, try using your sharpest lens on a portrait of your wife and see if sharpness is appreciated. That's the time when my cheapo 135mm flea market lenses come into their own because they flatter and sharpness doesn't.

Regards, David

PS this is getting like one of those how many pixels rows on other forums...
 
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I see that no one has really talke about the enlarging lens. It is the great equalizer. No matter how good your capturing lens is it still needs to go through an enlarging lens. This of course does not apply to those of you shooting and printing through your 50mm f3.5 Elmars. I always suggest getting the best resolution you can from the start. If you need blur you can always do it later. Or have an extensive lens kit with the sharp lens, the soft lens, and so forth. Really the lens should only be as sharp as you need to get the effect you want done.
 
taskoni said:
If the lens doesn't have to be sharp but the desired effect is a dead sharp photo how to do it then?
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Sharpness can mean two different things. If we work for the government, and we have to take the sharpest (most detailed) picture, then we need the lens with the highest resolving power. Maybe we are doing photo mapping from the air, and need to see a street sign from 10,000 feet. Or we work for the FBI and need to see a license plate from half a mile away. We might want an aspherical lens, or other highly corrected one, such as an apochromatic lens.

But there is a difference between a picture that high resolution, vs. one that just plain looks sharp. The subjective impression of sharpness isn't so much about resolving power; it's about local contrast. If there is a good bright light that creates high contrast edges, the picture will look sharp. A glancing sidelight will bring out detail and sharpness. And that impression of sharpness will not be lost on a fairly ordinary lens, as long as flare and internal reflections are under control.

A picture taken with a lens that has world-class resolving power, but so-so contrast, will look fairly ho-hum as far as creating an impression of sharpness. And even if the lens has good contrast, but the subject is lit with a diffuse, uncontrasty light, the picture still won't look sharp. You can still take a bad picture with the world's sharpest lens!
 
Nikkor AIS said:
In my experience, camera/lens movement, mirror slap as well as missing focus can be major contributing factors to degradation of image sharpness.
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It can be, but with good engineering, mirror slap can be totally neutralized as it has been, for example, in the Pentax K7. In other words, mirror slap used to be a problem; but now it's a solved problem. The focal plane shutter is still a problem — one solved in the Fuji X-100 by use of a leaf shutter.
 
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^---- ;-)

A bit more seriously, if you want to begin to really understand image resolution, contrast, and perceived sharpness, it would be hard to find a better white paper than this one, from Zeiss [PDF].
 
The Zeiss 100mm Makro mounted on a Contax RTS III is an unbelievable lens/camera combination. I don't know about talent, or lack of talent, but even in 35mm film lens/aperture/shutter/media/developer..or development all play a role in perceived sharpness. My first roll shot with the Zeiss was on Neopan 1600 developed in Rodinal and my jaw dropped when I saw the results. This wasn't expected given my choice of film/developer.
 
bwcolor said:
The Zeiss 100mm Makro mounted on a Contax RTS III is an unbelievable lens/camera combination. I don't know about talent, or lack of talent, but even in 35mm film lens/aperture/shutter/media/developer..or development all play a role in perceived sharpness. My first roll shot with the Zeiss was on Neopan 1600 developed in Rodinal and my jaw dropped when I saw the results. This wasn't expected given my choice of film/developer.
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I had the same reaction to Neopan 1600 in XTOL when I first started shooting the 35/2.8 C Biogon. Then, months later, I wet-printed from one of the negs, on a V35, and my jaw dropped a second time.
 
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We all love sharp lenses - at least I do. But I am not a pixel peeper - nothing could bore me more than taking dozens of shots in supposedly "ideal" circumstances to see how sharp lens X is at every f stop compared to lens Y. But some people seem to do little more.

In any event the reality is that all lenses are constrained by circumstances of shooting in the real world.

Too often I find that when I am shooting the lens sharpness is not the constraint. It will instead be that my focussing is not sufficiently accurate, or I am not braced sufficiently so am not steady enough, or my shutter speed has to be a tad too slow due to lighting or I have to shoot wide open. All of which affect image sharpness. And so often its not just about sharpness anyway. Colour rendition, bokeh, artifacts of optical abberations such as ghosting, fringing and all the other characteristics of lenses play a role in making an image that really jumps or totally "fritzing" it.

And when I get a sharp image, sometimes I find myself in Photoshop lowering its sharpness a tad due to it being too sharp - especially in portraits.


Albert Einstein once joked that a scientific theory should be as simple as possible - and no simpler. Perhaps something like this can be said for lens sharpness.

A lens should be as sharp as possible - and no sharper!
 
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Although the use of 1 / 250 and 500 "may" be sufficient to offset a 35 mm lens of the camera shake, this is not always the case, the entire screen with a moving object, you happen to use a heavy telephoto SLR.
 
The tell says that when Zeiss had got the Tessars on the market the pictures went too sharp and the first softnerlens had to be invented.
As always Zeiss made it work.

I had a pal who complained that even with his Hasselblade and Zeiss lenses he could not get sharp copies. His House moved his enlager with the traffic outside. Night coping solved the problem.

What do you want, how costly in money and time might it be?

Still when printed in a magazine or shown on a screen it don't have to bee that perfect. But for the pride and knowing it can't be too sharp. YMMV
 
johank said:
The tell says that when Zeiss had got the Tessars on the market the pictures went too sharp and the first softnerlens had to be invented.
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Nice idea. However, pictorialism and the associated fad for "portrait" soft lenses had already started years before the Tessar was invented and even longer before it became widespread. The soft lens craze probably is better considered a part of the youth movement of that period - using the outdated Petzvals of the grandfather generation to produce blurry nudes fits too well into the spirit of the time to be considered a isolated technical phenomenon...
 
A sharp lens is allways wellcome, but...
How sharp should it be? Does it really matter to the picture "story telling" ability?
IMHO, as long as the pìcture is a good one keeping the pùrpose of telling something to the viewer, a razor sharp lens is needless (if the photog is able to tell it).
Anyway, a good and sharp lens is wellcome.
Cheers
Ernesto
 
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