how to test a new lens, particularly the 24-70L II

[MM-5500]

Since there are reports of large variance in copy sharpness with the 24-70L ii, how can I test it to see if i got a good copy or  not?  How do I calibrate the lens to get the best performance with the camera.

I use the canon 5D III and I also have the 70-200L II

[PackLight]

Suggestion #1; Start with 4 copies, try them all out and send the 3 worst back.

Suggestion #2; Find a Buddy that has a really good copy, and if yours isn't as good or better send yours back. (Edit; I should point out if you do this, and your lens is actually better than his it can give you some ammunition to poke at him later because your pictures will obviously be better than his from your superior lens.) I recommend this method.

Suggestion #3; Find a technical camera geek on this site and offer him a couple hundred bucks to check your lenses out.

Suggestion #4 Try and do it yourself;

I would start by seeing if it need an AFMA through the entire range. Use Lensalign or Reikan Focal.

And do many of the tests in the blow article.

Roger at lensrental has a blog article about it, it would give you a go by to help check.

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

If you have some primes, or similar lenses I would take test shots and compare and use the ISO charts at TDP for a baseline.

Have Fun

[MM-5500]

Thanks Packlight for your reply.  read the article and it was helpful.  will be buying the lens later, wish me luck!

[PackLight]

Thanks Packlight for your reply.  read the article and it was helpful.  will be buying the lens later, wish me luck!

Good Luck; I think the most important thing in this purchase is a store with a good return policy. Switch out till you get one you like.

[mrmarks]

Since there are reports of large variance in copy sharpness with the 24-70L ii,

Where did you get this from? I would say in most cases, it is the user using some inaacurate method to assess and drawing some inaccurate conclusions. I think Canon's QC is pretty tight, and the 24-70L2 has a much better design than its predecessor to prevent element decentering. There was an article somewhere showing a teardown of the lens and the design was shown to be really robust. I got mine off the shelf randomly and no issues so far. Pretty pleased.

[PackLight]

Since there are reports of large variance in copy sharpness with the 24-70L ii,

Where did you get this from? I would say in most cases, it is the user using some inaacurate method to assess and drawing some inaccurate conclusions. I think Canon's QC is pretty tight, and the 24-70L2 has a much better design than its predecessor to prevent element decentering. There was an article somewhere showing a teardown of the lens and the design was shown to be really robust. I got mine off the shelf randomly and no issues so far. Pretty pleased.

Try here for where we heard,
 http://www.lensrentals.com/blog/2012/11/canon-24-70-mk-ii-variation

Or that Bryan at TDP took four copies to get a satisfactory copy

[mrmarks]

Sure, there's always some statistical distribution in any manufacturing (within SPC and specification limits) but as said in the review: "But I think you’d agree in real photographs it will probably be impossible to see the difference"

[PackLight]

Sure, there's always some statistical distribution in any manufacturing (within SPC and specification limits) but as said in the review: "But I think you’d agree in real photographs it will probably be impossible to see the difference"

No I don't agree. I had a copy of the old 24-70mm and it was on the low end of that chart. Very soft and eventually I got rid of it. I don't think it is acceptable to pay $2300 for a lens and to take a lens that is on the lower end of the performance chart.

Some people are reporting fall off on the 70mm end. There are a few things that I would expect of this lens. I would expect that it performs at least close to my 70-200mm f/2.8L II at 70mm. I would expect that the new 24-70 would meet or exceed the sharpness of my 35mm L and 24mm L at f/2.8.

While its true most photographers would never know if the lens they bought is lacking. I would know on my copy, for $2300 I expect the highest level of quality control and performance.

[Dylan777]

I tried 2 copies of 24-70 II from Crutchfield, both lenses have similar sharpness. I kept one and returned the other.

If the lens is soft, you will notice right away. With FoCal AFMA software, I still can't tell the different btw 865 sharpness to 900ish sharpness in real world.

Once your lens arrived, just go out take alot of pictures(at f2.8 on new 24-70) and review the pictures on 24" or bigger monitor. Keep it or not, you will know.

Enjoy your new toy

[pwp]

It's all right here at CR...
http://www.canonrumors.com/tech-articles/how-to-test-a-lens/

And buy from an authorized dealer with a clearly defined returns policy.

-PW

[infared]

I purchased a copy of the lens yesterday from B&H, which will arrive tomorrow, (if I can hunt down John, my UPS driver...$2300-signature required! LOL!). Now you guys have me all paranoid that I could get a bad copy!...as I recall, didn't Roger at Lens Rental test 5 or 6 copies and although he found variance in the copies, it was quite minimal and that he found all of the lenses to be aceptable in real world shooting?
I think a zoom lens HAS to have variance from copy to copy just because of variance in the zoom mechanism itself, say as opposed to a prime lens with no zooming mechanics...... There will be inherently more variance in zoom lenses in general just by the nature of the design. Kind of comes with the turf.

[Dylan777]

I purchased a copy of the lens yesterday from B&H, which will arrive tomorrow, (if I can hunt down John, my UPS driver...$2300-signature required! LOL!). Now you guys have me all paranoid that I could get a bad copy!...as I recall, didn't Roger at Lens Rental test 5 or 6 copies and although he found variance in the copies, it was quite minimal and that he found all of the lenses to be aceptable in real world shooting?
I think a zoom lens HAS to have variance from copy to copy just because of variance in the zoom mechanism itself, say as opposed to a prime lens with no zooming mechanics...... There will be inherently more variance in zoom lenses in general just by the nature of the design. Kind of comes with the turf.

infared,
I know how you feel right now I was little skeptical about the sharpness of this when I placed my pre-order. Why? I tried 3 different copies of mrk I in the past, all three were soft.

I even took half day off from work just to wait for the UPS guy.

Hope you will get the BEST copy. Keep us updated.

[PackLight]

I purchased a copy of the lens yesterday from B&H, which will arrive tomorrow, (if I can hunt down John, my UPS driver...$2300-signature required! LOL!). Now you guys have me all paranoid that I could get a bad copy!...as I recall, didn't Roger at Lens Rental test 5 or 6 copies and although he found variance in the copies, it was quite minimal and that he found all of the lenses to be aceptable in real world shooting?
I think a zoom lens HAS to have variance from copy to copy just because of variance in the zoom mechanism itself, say as opposed to a prime lens with no zooming mechanics...... There will be inherently more variance in zoom lenses in general just by the nature of the design. Kind of comes with the turf.

In his article I linked Roger had checked 70 copies now, 3 were bad by their standards.
I think lensrental's standards would be a bit less than I would demand of my purchase. They would probably keep in their stable any lens either on the low end of testing or high just because it is in the range that a typical batch of lens would fall. Most people renting will be satisfied with its performance. I wouldn't want to spend that much of my hard earned money for my only 24-70mm II and then know I had a lens that was on the low end.

[infared]

infared,
I know how you feel right now I was little skeptical about the sharpness of this when I placed my pre-order. Why? I tried 3 different copies of mrk I in the past, all three were soft.

I even took half day off from work just to wait for the UPS guy.

Hope you will get the BEST copy. Keep us updated.
[/quote]

Dylan...so how is your copy of the lens? Did you shoot any test charts on do any extensive testing?
(I am hunting John, my UPS driver, down in the MORNING!!! i know his route. LOL! He delivers to me at the end of the day..but I am afraid I will miss him cause I  have to sign for this, he cannot leave at my door). I want the lens for the weekend as my photo buddy and I are going on an overnight to our favorite shooting location and I definitely want this lens in my quiver to test it out!

[Dylan777]

@ infared:

Both copies I received from Crutchfield were sharp.

Before AFMA
1. I set the camera on tripod and took some pictures with View finder at 24, 35, 50, and 70mm at f2.8 ISO 100. My target was stucco wall

2. Same setting, under LiveView, took some pictures at 24, 35, 50, and 70mm at f2.8 ISO 100

I didn't see much different btw viewfinder Vs LiveView

3. I ran the lens through FoCal(x50 lenght) and repeated the steps above

Results: FoCal suggested -2 @ 24mm(sharpness around 1100) and +1 at 70mm(sharpness around 1150ish)

Again...I compared pictures before AFMA Vs after AFMA, there is no different in real life shooting. At the end, I set both ends(W+T) to zero on my 24-70 in my 5D III.

I didn't know at 24mm this lens has vignetting, so I asked Crutchfield for another copy. 2 weeks later, Crutchfield sent me my replacement. I compared two lenses. Same vignetting. According FoCal, the 2nd copy is a bit sharper. AGAIN...no different btw the two - in term of sharpness in real life shooting.

At the end, I kept the 2nd copy and returned the 1st. Here is my most recent pix I took inside a pre-school class room with no flash at f2.8 (5D III +24-70 II)