Is your lens sharp enough?


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melcheong72

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Mar 22, 2006
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#1
How to determine if your lens is a sharp copy?

Any recommendations?

1. Do macro test?
2. Check at which aperture?
3. What subject to take for the test? Newpapers?
4. Must be tripod mounted else test is void?
5. Test at minimum focal or max focal length? Or Macro?
6. If you can only do 1 picture test, how would you take the picture?


Thank you.
 

Aug 16, 2005
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#2
Who cares so much if you lens is the sharpest copy or not....
Just go out there and shoot with it..
once you get your composition skills, you won't worry that much about sharpness lest you blowing it to Super 8R.
Unless your lens has got serious miscalibration or Back/Front focussing issues, than that is a diff prob.
 

Jun 27, 2002
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#3
JediForce4ever said:
Who cares so much if you lens is the sharpest copy or not....
Just go out there and shoot with it..
once you get your composition skills, you won't worry that much about sharpness lest you blowing it to Super 8R.
Unless your lens has got serious miscalibration or Back/Front focussing issues, than that is a diff prob.

i agree.
 

jopel

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Dec 21, 2004
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#4
JediForce4ever said:
Who cares so much if you lens is the sharpest copy or not....
Just go out there and shoot with it..
once you get your composition skills, you won't worry that much about sharpness lest you blowing it to Super 8R.
Unless your lens has got serious miscalibration or Back/Front focussing issues, than that is a diff prob.
even if the lens cost few thousand dollars you don't bother about the quality of it.
 

zaxh81

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Jan 29, 2003
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#6
JediForce4ever said:
Who cares so much if you lens is the sharpest copy or not....
Just go out there and shoot with it..
once you get your composition skills, you won't worry that much about sharpness lest you blowing it to Super 8R.
Unless your lens has got serious miscalibration or Back/Front focussing issues, than that is a diff prob.
thread starter never state sharpest lens leh.
 

sORe-EyEz

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Jun 28, 2005
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#7
i nv develope pics so big till i can tell if my lense is sharp. :sweat:

4R pic, cheapo lense will do fine.
 

sk.images

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Dec 9, 2005
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#9
Seriously, how many lenses come out of the factory out-of-spec? I would guess very few, yet, there is this paranoia about getting the sharp(est) lens - you might test 5 lenses in a store and say number 3 is sharpest I will buy that - how do you know that this lens is as sharo as it could be. And doing a short test in-store and viewing in the viewfinder is going to be of little use.

If you're buying a warrantied lens then buy whichever and then do your tests in your own time - if you're not happy take it to the manufacturer and within a couple of days you have a sharp lens (please no stories about how it took 35attempts to get your lens sharp). I'm guessing that you will be happy with the lens straight out of the box.
 

Witness

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Mar 18, 2004
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#10
actually.....some lens are indeed softer than the rest.... u may not be blowing up to s8r...but i suppose most screens are at least tt size ya... haha
 

waileong

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Feb 5, 2003
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#13
Agree that sharpness is not the be-all and end-all of a lens (there's contrast, colour, bokeh, etc), but once you actually develop the compositional skills, you will rue the day you decide not to worry about sharpness.

Note that we're not talking about lens A being sharper than lens B in terms of lpm, but is lens A as sharp as it should be, based on the spec it was built to. In other words, any misalignment, any adjustment out of whack, etc.

S8R is very small, not a test of sharpness at all. Go to A3 minimum, or blow it up 5 feet on a slide projector if you really want to see sharpness.

It's very irritating, once you are good enough with composition, to see that the eyes are slightly out of focus, once you enlarge a picture. Esp. if you have a full-frame DSLR and you know that A3 or larger enlargements are actually well within its capability.

Wai Leong
===
JediForce4ever said:
Who cares so much if you lens is the sharpest copy or not....
Just go out there and shoot with it..
once you get your composition skills, you won't worry that much about sharpness lest you blowing it to Super 8R.
Unless your lens has got serious miscalibration or Back/Front focussing issues, than that is a diff prob.
 

smallaperture

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Jan 5, 2004
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#14
Maybe, we should phrase the question in another way: How easy is it for you to get sharp pix with the lens?

A Fast AF so that you capture your moving target :bigeyes:
B Aperture big enough so that it is easy to lock focus and no hunting (at least F5.6)
C Tripod collar to use monopod or tripod
D VR / IS / OS etc a good-to-have luxury :thumbsup:

And how easy it is to blame the equipment when we don't get it as sharp as the Joneses :nono: , resulting in the "BBB" syndrome. :bsmilie:
 

melcheong72

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Mar 22, 2006
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#17
Seems that some of the guys here may have mis-read.

I never said about getting the sharpest copy (anyone will know you will never know unless you do QC at the factory)

What I am asking if how should I do a test to check for sharpness in the most effective and efficient manner. For example, I may be testing out a used lens (no warranty) in TCW or any camera shop, and would like to quickly shoot for sharpness test. That is why i even wrote thr last point in my first post (if I only can do 1 picture test...)

My england so poor meh ... why most dun understand and interprete as I am some paranoid wanting the best of the world??
 

lsisaxon

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Nov 29, 2004
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#18
melcheong72 said:
Seems that some of the guys here may have mis-read.

I never said about getting the sharpest copy (anyone will know you will never know unless you do QC at the factory)

What I am asking if how should I do a test to check for sharpness in the most effective and efficient manner. For example, I may be testing out a used lens (no warranty) in TCW or any camera shop, and would like to quickly shoot for sharpness test. That is why i even wrote thr last point in my first post (if I only can do 1 picture test...)

My england so poor meh ... why most dun understand and interprete as I am some paranoid wanting the best of the world??
Let's face it.. not all lenses are made equal. If you want to know if a lens is sharp, get a high megapixel count camera like D2X, D200, EOS1DsMkII or EOS5D, set sharpening to off and shoot at max resolution. Then zoom in to 200% magnification and see how sharp the sharpest part of the image is. If the fine transitions do no spread over 3 pixel width, then the lens can be considered sharp enough. But be prepared to spend a lot more money if you want a lens that is able to resolve to 2 pixels on that kind of resolution.
 

waileong

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#19
Actually that's the problem. To do a good test, you need the following:

First, you need to ask the uncle to give you a tripod to put the camera on.

Second, you need a high-res body (like a 1Ds Mark II)-- I hope you happen to bring it along.

Third, you need a notebook or PC to view the image at full res or even 200%-- LCD display not good enough.

Fourth-- hopefully you were able to shoot a good test target (eg USAF 1951 chart or newspaper), otherwise evaluating sharpness is more difficult.

If you just anyhow use a 300D, shoot your friend's face handheld, if the picture is not sharp, how would you know if it's the lens, the camera or your lousy handholding?

To answer your questions specifically:

1. Do macro test?

* Only if your lens is a macro lens

2. Check at which aperture?

* That's the problem. All lenses improve when you stop down. If you test at f8, the lens will be sharper than at f2. But you may not be able to shoot at f8 in the shop without a lot of noise introduced in the image.

3. What subject to take for the test? Newpapers?

* I guess any target with straight lines will be good.

4. Must be tripod mounted else test is void?

* Of course. Else who know if your qi gong good enough or not. And the target must also be still. That's the tough one.

5. Test at minimum focal or max focal length? Or Macro?

* That's the other problem. All zoom lenses have an optimal focal length, and it's usually not the longest or shortest, so if you test at those focal lengths, you may find it's not as sharp as somewhere in the middle.

6. If you can only do 1 picture test, how would you take the picture?

* I would not take just one picture. It would be a waste of time.

* I would try the following:

* Choose a target at the appropriate distance for lens (eg if it's a portrait lens, maybe choose 2 m)
* Measure distance from sensor to target.
* Turn off AF.
* Set distance on lens.
* Shoot at various focal lengths.
* Shoot at various apertures
* Repeat above, adjust the distance setting slightly over and slightly under the measured distance.
* Check sharpness of pictures.


Note: The above procedure is basically to check if your lens is calibrated correctly. That is, if the real distance (measured with a ruler, etc) is 2 meters and the lens is set to 2 m, is the picture sharp? Or must the lens be set to 2.1 or 1.9 for the picture to be sharp?

This is because the capability of a lens is already determined when it was designed. In other words, an L lens is sharper than a non-L lens simply because it is designed to be sharper (and more expensive). So there is no point measuring sharpness per se.

What is important is whether the lens is correctly calibrated. If someone dropped the lens, for example, the calibration could be off, so that the focused distance may differ from the true distance to the target. This will result in unsharp pictures.

That's what I'm trying to measure here.

Wai Leong
===
melcheong72 said:
What I am asking if how should I do a test to check for sharpness in the most effective and efficient manner. For example, I may be testing out a used lens (no warranty) in TCW or any camera shop, and would like to quickly shoot for sharpness test. That is why i even wrote thr last point in my first post (if I only can do 1 picture test...)
 

student

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Jul 26, 2004
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#20
Two more things to consider

1 Use a cable release

2 Use mirror lock-up.

You do not want any camera shake to affect the resolution.

Unless the lens has obvious faults, life is a lot easier if you forget such things.
 

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