Testing a lens

Soldato
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Bit of a hypothetical one this, but hopefully some use will come of it.

Let's assume we've just bought a lens or two. Or, more accurately, you've bought them and have 7-days in which to test that they are as good as they should be, given that that this kit is your livelihood and you need it to be right, first time.

How would you go about testing the lenses in order to ascertain this? Assume you have access to whatever Canon or Nikon body/bodies you need along with a fairly decently-sized working area (and obviously access to the Great Outdoors) and whatever else you need, within reason.

What would you do?
 
Soldato
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I would put the lens on a camera and check autofocus is snappy and there are no odd noises.

I'd then take a few test shots, i.e bright sky through trees for CA and a detailed even scene for sharpness (tripod mount camera and check a few apertures). Look at the four corners plus centre at 100% on pc.

If after that nothing seems out of the ordinary, then it must be alright:)

However, I've never done anything like that! I normally just whack it on and go out shooting...

I don't think there's any need to set up test charts and mess about with mtf graphs etc. You'll know if somethings wrong just by looking at a range of normal shots.
 
Soldato
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I would put the lens on a camera and check autofocus is snappy and there are no odd noises.
Sorry, sorry, I should have said - I'm talking mainly optical tests here, not just electronic.

However, I'd say you're spot-on with your initial assessment.

I'd then take a few test shots, i.e bright sky through trees for CA and a detailed even scene for sharpness (tripod mount camera and check a few apertures). Look at the four corners plus centre at 100% on pc.
All well and good, but given than you don't have another copy of the lens to compare this against, how accurate would you say this test is in determining the optical 'quality' of said lens?

I don't think there's any need to set up test charts and mess about with mtf graphs etc.
But do you know anything about them? If you do, I'd love to hear your musings.
 
Soldato
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All well and good, but given than you don't have another copy of the lens to compare this against, how accurate would you say this test is in determining the optical 'quality' of said lens?

It's accurate enough for me:) I know what a sharp lens looks like, I've got 3, and one duff one!

But do you know anything about them? If you do, I'd love to hear your musings.

Not really. I know that when I get to that point in a review I skip a few pages!

Tbh, as long as it lives up to your expectations and you love the results, then it's fine. Some people get so hung up on it and keep sending lenses back again and again. I trust canons QA to get it right straight out the factory, not my eyesight. If a lens is slightly off, my sights good enough to know anyway.
 
Soldato
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Putting the camera & lens on a tripod and shooting a brick wall is a good test for pincushion and barrel distortion. Obviously, make sure you're square to the wall! Then pin up a large sheet of newpaper and the photos will tell you about the differences between the centre & edge of the lens and possibly how flat the plane of focus is.
 
Associate
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For me, distortion is something which will be inherent to the model of lens anyway - whether it's a good copy or not, it should carry very similar distortion levels (correct me if I'm wrong tho!). So I wouldn't be worried about distortion

I would be testing sharpness, and AF precision and accuracy - as I would assume that these are the key factors that are most likely to change between copies of the same lens. Perhaps CA as well, but I can't see this being as variable as AF and sharpness.

I think if you have only one copy of the relevant lens, the only way to get a feel for whether it is a comparatively good copy or not would be to use some sort of test chart (not that I've ever done this!) so that you can compare results with other owners/reviewers of the same lens. It sounds a bit OTT, and I can definitely see Stupot's point of taking a more pragmatic and real world assessment - but I'm saying this purely on the basis of the OPs text shown below:

...given that that this kit is your livelihood and you need it to be right...

Consider me subscribed to this thread - I'll be interested to learn the views of others with more experience than me! :)
 
Associate
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I use a lens test panel (piece of paper with lines etc printed on it).
 
Associate
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Best way is to go out and shoot with it - if you cant see anything wrong with the results and the sharpness contrast are about what you`d expect from that model of lens then you have a keeper.

With most lenses you should know straight away if they are any good or not. I am not one for all the pixel tests etc.
 
Soldato
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I use a lens test panel (piece of paper with lines etc printed on it).

some say thats the worst way to check as it tests the lens out of its comfort zone which distorts the results.

best way to check a lens is to actually use it and see if youre happy with the results.
 
Associate
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some say thats the worst way to check as it tests the lens out of its comfort zone which distorts the results.

best way to check a lens is to actually use it and see if youre happy with the results.

Hmm I half agree.

A test panel will test the lens to the extremes, and might show an issue that a few test shots wouldn't.

But I also take a fair few "test" shots too to make sure.
 
Associate
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Or, more accurately, you've bought them and have 7-days in which to test that they are as good as they should be, given that that this kit is your livelihood and you need it to be right, first time.

Typically I just use it and if it works - nice. If not - oh dear. TBH in all the lenses I've used, I've only ever used one that seemed a little off. I think the fears of QC are pretty unjustified - 95% of lenses are good. Of those 30% are going to be better than average and the other 5% are probably a little off.

Although in all honesty, I do test the AF on anything 200mm+ by getting someone to run at/away/zig-zag etc. to the camera and check it focuses quickly and accurately with my body. So I'll fire huge 50 shot 8fps bursts, If it's less than 90% I'll check if it's user error or a poop lens.

Then, the ultimate test is to see if by using that kit your earning more. If not, you sell it. If your earning more with it, keep it. (or if you feel more comfortable/your producing better stuff)
 
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