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Recommenations for checking a new lens?
  
 
Cougar281
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p.1 #1 · p.1 #1 · Recommenations for checking a new lens?


I just picked up both a new (to me) 70D in quite good condition with about 50k actuations on it from a local shop and an EF 24-105mm f/4L IS II from B&H.

Going back, I had a EF 28-135 that I was never happy with (others may not be as picky as me). As I recall, it was too soft across the entire spectrum, and it had a horrible issue with the camera focusing that lens roughly 1" behind the intended focus point. I suspect I just got a bad copy as I took some pictures with mine, then took the same pictures with a friends 28-135 and the pictures with his were better. I traded that off when I got my 40D, and since then, have been using just a 50mm f1.8 and 24mm f2.8.

So I finally bit the bullet and bought some L glass. From reading around, the 24-105 f/4L II sounds to be a really good lens. Some say it's better than the first gen, some say it's not quite as good, but in the end, it doesn't seem like anyone's hating on it. Overall, I think it should be a really good 'walking around' lens. Certainly better than either a 24mm or 50mm (not that there's anything wrong with either of them, but using just those two is quite limiting).

Anyway, I've only played around with it a little (just got delivered late this evening), and on the surface, it seems quite sharp at 105mm, but perhaps a little soft at 24mm. Could just be me though.

Does anyone have any suggestions for repeatable testing to see how the lens performs other than just 'get out and shoot'?



Aug 30, 2017 at 04:50 AM
jeetsukumaran
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p.1 #2 · p.1 #2 · Recommenations for checking a new lens?


Roger Cicala over at LensRentals goes over this quite well here:

https://www.lensrentals.com/blog/2010/11/how-to-test-a-lens/



Aug 30, 2017 at 05:39 AM
Paul Mo
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p.1 #3 · p.1 #3 · Recommenations for checking a new lens?


I am not highly technical, but with this lens I'd tripod my camera with a remote and run through focal lengths of: 24 - 35 - 50 - 85 - 105 - while running through apertures of: f4 - 5.6 - 8 - 11.

For interest's sake I might run the same with IS on and then off.

Then I'd do the same handheld.

I tend to choose cars photographing their badges and tail lights - which are high contrast, graphically sharp and can show up CA.

Import into Lightroom, make a coffee and peruse.

That'd tell me most of which I'd need to know apart from AF performance when tracking, low light AF performance, et al.




Aug 30, 2017 at 06:24 AM
dhphoto
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p.1 #4 · p.1 #4 · Recommenations for checking a new lens?


The most common fault I have found is decentering where one of the sides of the image isn't as sharp as the other because a lens element is misaligned, this can happen at one particular point with a zoom or throughout the range, so I would find a subject with something in all four corners and shoot that at different lengths and apertures and have a good look.


Aug 30, 2017 at 07:12 AM
AlexDROP
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p.1 #5 · p.1 #5 · Recommenations for checking a new lens?



dhphoto wrote:
The most common fault I have found is decentering where one of the sides of the image isn't as sharp as the other because a lens element is misaligned.


Nice point to mention. It particularly happens due to IS impact. I would advise to put the camera with the lens in vertical position on the lens blend, halfpress the shutter button to activate IS and after its activation is finished simply turn it off on the lens barrel. In such way you eliminate its impact and can test the lens IQ. If the sharpness all over the frame is still unequal then the lens is descentered.

That is why I never use IS with my wide angle zooms such as 16-35/4 IS and 24-105/4 IS if I need ultimate IQ.



Aug 30, 2017 at 07:24 AM
 

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jcolwell
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p.1 #6 · p.1 #6 · Recommenations for checking a new lens?


AlexDROP wrote:
That is why I never use IS with my wide angle zooms such as 16-35/4 IS and 24-105/4 IS if I need ultimate IQ.


...when using a tripod.




Aug 30, 2017 at 01:16 PM
AmbientMike
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p.1 #7 · p.1 #7 · Recommenations for checking a new lens?


"Repeatable" makes things a lot harder. You'd probably have to have a consistent light source to do this, the easiest way is flash, but the high contrast lighting tends to make things look good. Lighting affects how sharp your pictures are.

You could use room lighting, but I don't know if it is consistent. If you do a test today, I don't know if the bulb is the same in 6 months, if you tested a different lens. It would be easy to get a different bulb, if that one burns out, but I really don't know if a different temperature bulb, say 2900K vs. 5200K, or whatever is available, would give different results. I kinda think it would.

As far as test targets, 1951AF, newspapers, and brick walls have all been used.

Be sure to test for focus shift.



Aug 30, 2017 at 06:15 PM
scalesusa
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p.1 #8 · p.1 #8 · Recommenations for checking a new lens?


There are some lens properties that indicate a issue with the lens, and some that are just part of the design.

Assuming you want to test the functionality of the lens, test for decentering, google it, there is a lot of information. Then test for focus accuracy at two or three distances, and at two or three zoom ratios.

Note: Live Autofocus using DPMA is going to be very accurate, so you can compare with and without. Properties like focus shift are part of a lens design, no need to test for it, its well documented for the affected designs.



Aug 30, 2017 at 08:42 PM
Cougar281
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p.1 #9 · p.1 #9 · Recommenations for checking a new lens?


Thanks for the tips - I'll do some reading and then hopefully get to do some testing/experimenting next week.


Aug 31, 2017 at 12:18 AM
Cougar281
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p.1 #10 · p.1 #10 · Recommenations for checking a new lens?


Just a quick report back - I haven't gotten a chance to do any of the testing, but so far, based on the pictures I've taken with it so far (along with the 70D vs the 40D), I''m loving it way more than I ever liked the 28-235 I had.... While it's not exactly a prime lens, so far, it's pretty darn good in my opinion. But I do still want to do a more 'scientific' test to try to be sure I got a good 'copy'.


Sep 12, 2017 at 06:21 AM







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