Soft lenses

Chivs33

Chivs33

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Ben
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Hi,

how do most tell if the new lens they have purchased is a soft copy if nothing to compare to? I often here of people sending back lenses to exchange for another, but how can you accurately tell if you cannot compare to the same lens?
If I purchased a 16-35 F4, a friend of mine has the same lens and could do a few test shots to make a comparison, but where this can't be done is it just the case that experience prevails?

Ben.
 
You could try shooting a test chart if you are feeling particularly geeky :)

http://bobatkins.com/photography/technical/lens_sharpness.html

Many of the issues are seen by DSLR users who need to micro adjust some of their lenses for best focusing accuracy. If you're using a mirrorless camera then this won't be a problem...any blurriness is likely to be a dodgy lens rather than a calibration issue.
 
manualfocus-g said:
You could try shooting a test chart if you are feeling particularly geeky :)

http://bobatkins.com/photography/technical/lens_sharpness.html

Many of the issues are seen by DSLR users who need to micro adjust some of their lenses for best focusing accuracy. If you're using a mirrorless camera then this won't be a problem...any blurriness is likely to be a dodgy lens rather than a calibration issue.
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Is it the case if it's a bad copy it will be quite obvious? How can you tell if it's a soft copy or how the lens is but just doesn't meet expectations?
 
Chivs33 said:
Is it the case if it's a bad copy it will be quite obvious? How can you tell if it's a soft copy or how the lens is but just doesn't meet expectations?
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I'd read some reviews of the lens in order to set your expectation first. If you buy a lens that is supposed to be sharp across the frame at f/5.6, but you shoot a test chart and see the right hand side is all blurry, then you can be pretty sure that it's naff :)
 
good lenses are supposed to be very sharp. Simply sharp, not a little soft, etc. If anything at all looks suspicious where you don't expect it to be it almost certainly is f***ed. Usually it is one edge that is way worse, or it is a complete disaster altogether.
 
I see lots of queries from people who have bought an f1.4 lens of supposedly good quality and are distressed that it's not sharp at f1.4. There are few lenses that are sharp in the centre at f1.4 and even fewer that have sharp edges at f1.4. It also depends what you mean by "sharp". Even those that are said to be sharp at f1.4 get sharper as they're stopped down, which leads some customers to complain that their copy isn't sharp wide open.

If you want to compare two copies of the same lens you can rent an extra one, or you can buy two and return one. But you have to have good experimental technique, which includes being able to do accurate manual focusing. Most people who complain in photography forums about their soft lens can't reliably shoot a sharp shot. If you shoot a test scene, then take the lens off, put it back on, and shoot the test again, and find that one shot is sharper than the other, that kind of random variation could mislead you into choosing to send the sharpest lens back by mistake.

The worry is spending a lot of money on what later turns out of be a duff lens. To avoid that worry first learn how to get the sharpest possible shots you can from the lens(es) you've got. Once you know you can do that, you'll have confidence in your ability to check a new very expensive lens out in time to return it if it's a bad one.
 
chris malcolm said:
I see lots of queries from people who have bought an f1.4 lens of supposedly good quality and are distressed that it's not sharp at f1.4. There are few lenses that are sharp in the centre at f1.4 and even fewer that have sharp edges at f1.4. It also depends what you mean by "sharp". Even those that are said to be sharp at f1.4 get sharper as they're stopped down, which leads some customers to complain that their copy isn't sharp wide open.

If you want to compare two copies of the same lens you can rent an extra one, or you can buy two and return one. But you have to have good experimental technique, which includes being able to do accurate manual focusing. Most people who complain in photography forums about their soft lens can't reliably shoot a sharp shot. If you shoot a test scene, then take the lens off, put it back on, and shoot the test again, and find that one shot is sharper than the other, that kind of random variation could mislead you into choosing to send the sharpest lens back by mistake.

The worry is spending a lot of money on what later turns out of be a duff lens. To avoid that worry first learn how to get the sharpest possible shots you can from the lens(es) you've got. Once you know you can do that, you'll have confidence in your ability to check a new very expensive lens out in time to return it if it's a bad one.
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x2.

Plus, sometimes - and this affects mainly large aperture lenses (>f2) - it's not a question of the lens being sharp or not, it's a question if the lens partners well with the body regarding AF, because the same lens in two different bodies may perform very different. Sometimes they just need to be calibrated together.
 
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I believe that a lot (admittedly not all ) of "soft" lenses are soft due to user error.
I do know what you mean about user expectations though.
I bought a Nikon 135 f2 DC lens, and despite spending ages adjusting the micro focus adjust in the camera, still wasn't satisfied.
It was sharp as a razor stopped down, but I wanted the creamy bokeh wide open at f2, which is why I bought it (for portraits).
So I stopped pixel peeping, went out and used the lens and got a surprise.
The more I used it, the sharper it became !!
There are certain lighting conditions for example, where the lens isn't at it's best, but now I know about these "limitations", I can adjust my shooting technique slightly to make the problem go away.
As I became more familiar with the characteristics of the lens, and by using it a lot, my keeper rate shot up.

All I'm saying is don't get too hung up on sharpness, unless the lens is waaayyy out, just go and enjoy shooting the lens.
You may be pleasantly surprised.
 
Chivs33 said:
Hi,

how do most tell if the new lens they have purchased is a soft copy if nothing to compare to? I often here of people sending back lenses to exchange for another, but how can you accurately tell if you cannot compare to the same lens?
If I purchased a 16-35 F4, a friend of mine has the same lens and could do a few test shots to make a comparison, but where this can't be done is it just the case that experience prevails?

Ben.
Click to expand...

Simple

If the shot look ok, it's fine.

If it looks sh1t without human error, there's an issue.
 
daugirdas said:
good lenses are supposed to be very sharp. Simply sharp, not a little soft, etc. If anything at all looks suspicious where you don't expect it to be it almost certainly is f***ed. Usually it is one edge that is way worse, or it is a complete disaster altogether.
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All lenses are slightly de-centred IMHO. One little knock and they go from tolerable to hopeless in my experience.
 
ST4 said:
All lenses are slightly de-centred IMHO. One little knock and they go from tolerable to hopeless in my experience.
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Depends on the brand/build quality I guess. I have lenses from the early 80s that are still stunningly sharp at infinity. I had a Nikon AIS 24/2.8 that looked like it had been run over by a tram, backwards, and still performed beautifully :D
 
manualfocus-g said:
Depends on the brand/build quality I guess. I have lenses from the early 80s that are still stunningly sharp at infinity. I had a Nikon AIS 24/2.8 that looked like it had been run over by a tram, backwards, and still performed beautifully :D
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My Zeiss distagon was dreadful, awfully decentred, they fixed it, then it just went back to its old very soft in the corners and sharp in the middle ways, even at F11!!!

Never dropped it, just lived on a body and in a camera bag. The Nikkor made lenses have been much more reliable. 100% view and it looked OOF in the edge, sharp in the middle. Crazy
 
I have one lens which got seriously decentred when my assistant kicked it across the room (by mistake) and another which was totally wrecked by a lesser drop. I have a few other lenses which have suffered just as nasty knocks, in one case definitely a lot nastier, without losing any of their excellent optical quality. Nothing to do with cost or metal vs plastic. I don't think you can make general rules about these things.
 
manualfocus-g said:
Depends on the brand/build quality I guess. I have lenses from the early 80s that are still stunningly sharp at infinity. I had a Nikon AIS 24/2.8 that looked like it had been run over by a tram, backwards, and still performed beautifully :D
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Wowsers :o No probs with my Contax/Yashica mount Distagons/Planars/Sonnars...won't bother with the new versions then lol
 
Roger Cicala of LensRentals has done a few articles on the myth of 'soft' copies of lenses. His testing has shown that real problems are obvious. LINK
 
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