24-70 2.8L - Softness and Focus issues explained by Canon Tech

My 10 month old 24-70 is back with Canon today, for the third time. To be honest, I've never really been happy with it, and last week when I needed it to perform, it failed me again.

Anything at 2.8 = Super Soft
Focusing issues (back focus)
Horrible CA

This week, I needed it again and didn't trust it. I borrowed a friends lense (same lense) and it was fabulous! I am convinced that mine is a lemon.

So I sent it back to Canon and demanded a replacement, and today the Canon tech (hong kong) called me to 'explain'. This is what he said:

1. The lense is 'pretty much' within specs.
2. There is some problem with the central point not being in the center, and this is probably the cause of the softness and CA.
3. Because I leave the lense on the body, and sit it on a table (with the lense end resting on the table) - the lense collar has become loose and has to be replaced.

Now, this really sounds ridiculous to me. Dont you guys leave your 'bricks' on your bodies and just sit them on the table? This is supposed to be a workhorse, L series lense, and its not able to sit at an angle?

I really dont get it...can anyone with this lense (which works properly) explain?

ps. Canon Zealots can ease off, this is not 'user error' - i have tested and done the focus test, as well as real World use. This lense has horrible quality control.

It would be good to put some posts up for us to see.

I have rummaged around and found this post: https://photography-on-the.net/forum/showthre​ad.php?t=412865

First thing I see here is a focus tests, commenting on that:

a) I don't like this test chart, the AF system has a sloping target with differing ranges over the area of the test focus point. It may or may not make a difference but I suggest this chart which resolved that source of systematic errors with a little targeting flag. http://www.canon-dslr.com …/Canon_SLR_Focu​s_Test.htm

b) Canon's AF accuracy requirements are clearly defined in terms of depth of focus (depending on body type). But we can't tell if you are in that limit or not without knowing the shift in focus plane on the test target and the target distance (so we can convert depth of focus into depth of field).

c) There is some variation from shot to shot on AF accuracy. A good technique is to take several shots spinning the focus to MFD and infinity before reactivating the AF and taking another shot. Discard the outliers. (BTW regarding your check with a 50/1.4 this lens I found to have a very wide variation in AF precision from shot to shot)

Are you getting absolutely no rightly focused image with your lens?

Let your friend try your copy of 24-70L, and see what he thinks of it.

Give him your camera too if you can.

maxxed wrote in post #4504345
My 10 month old 24-70 is back with Canon today, for the third time. To be honest, I've never really been happy with it, and last week when I needed it to perform, it failed me again.

Anything at 2.8 = Super Soft
Focusing issues (back focus)
Horrible CA

This week, I needed it again and didn't trust it. I borrowed a friends lense (same lense) and it was fabulous! I am convinced that mine is a lemon.

So I sent it back to Canon and demanded a replacement, and today the Canon tech (hong kong) called me to 'explain'. This is what he said:

1. The lense is 'pretty much' within specs.
2. There is some problem with the central point not being in the center, and this is probably the cause of the softness and CA.
3. Because I leave the lense on the body, and sit it on a table (with the lense end resting on the table) - the lense collar has become loose and has to be replaced.

Now, this really sounds ridiculous to me. Dont you guys leave your 'bricks' on your bodies and just sit them on the table? This is supposed to be a workhorse, L series lense, and its not able to sit at an angle?

I really dont get it...can anyone with this lense (which works properly) explain?

ps. Canon Zealots can ease off, this is not 'user error' - i have tested and done the focus test, as well as real World use. This lense has horrible quality control.

1. I suspect they are talking just focus accuracy here. That seems to be your only issue at least on centre, I presume you were OK with the manual focus result you had.

2. I am not sure what this means, sounds like they are talking about element decentering.

3. I am fairly careful to pickup lenses weighing a Kg or more by the lens (I have a light semi pro body) but this comment does not make much sense to me.

It's lens not lense.

Can you put up some of your corner CA examples as a 400% crop please.

Being a wide angle at 24mm it will have some CA. On a 350D photozone measured 1.25 pixel http://www.photozone.d​e …s/canon_2470_28​/index.htm

Scaling this up for a 40D that might be say 1.5 pixel. Note, photozone tests at low magnifications and CA can increase at higher magnifications. I consistently measure higher CA values than they do because I test at higher magnification.

If you have 1.5-2.5 pixels of CA in the corner at 24mm I think you have nothing to complain about. You should be able to reduce this to next to nothing in photoshop or with the new version of DPP easily.

I put mine through hell regularly and it has NEVER let me down... I leave the lens on the body all the time.

Double Negative wrote in post #4504532
I put mine through hell regularly and it has NEVER let me down... I leave the lens on the body all the time.

True, I leave my 100mm macro or 24-105 or whatever on the body in storage; but I don't tend to store it on the table.

I do leave a 300/4 IS + 2X on the body for long periods resting on a table when waiting for birds in the garden; I don't like to leave kit on a tripod, even a big one, unattended.

Huh, well if you cant set it on the table what are you supposed to do with it? It ask the Canon tech that. What is the proper way to leave it for a while? Only off the camera?

Pasukun wrote in post #4504514
Let your friend try your copy of 24-70L, and see what he thinks of it. Give him your camera too if you can.

I've done this and he's the one who really pushed me to give Canon an ultimatum about this lense. Usually on forums everyone will tell you its 'user error' and so you start to believe it. He confirmed otherwise.

Lester Wareham wrote in post #4504487
It would be good to put some posts up for us to see.

I have rummaged around and found this post: https://photography-on-the.net/forum/showthre​ad.php?t=412865

Hi and sorry for not referencing this. I started a new post as that old thread was specifically to check the focusing errors I was seeing. I generally dislike focus charts, but when 'real world' shooting proves to yield negative results, I use that as a fallback.

My main issue here is that Canon is saying everythings 'ok'. Now, if I were to ask ANYONE with a sharp copy of this lense to trade with me, I would have zero takers.

Im just wondering if I should refuse to take it back from Canon now...

maxxed wrote in post #4504725
Hi and sorry for not referencing this. I started a new post as that old thread was specifically to check the focusing errors I was seeing. I generally dislike focus charts, but when 'real world' shooting proves to yield negative results, I use that as a fallback.

My main issue here is that Canon is saying everythings 'ok'. Now, if I were to ask ANYONE with a sharp copy of this lense to trade with me, I would have zero takers.

Im just wondering if I should refuse to take it back from Canon now...

If the mount has been fixed then it might solve the problem, you need to test it if so.

Is this a warranty repair? If so that might explain the nonsense about the table, they just don't want to pay for it.

maxxed wrote in post #4504725
Hi and sorry for not referencing this. I started a new post as that old thread was specifically to check the focusing errors I was seeing. I generally dislike focus charts, but when 'real world' shooting proves to yield negative results, I use that as a fallback.

My main issue here is that Canon is saying everythings 'ok'. Now, if I were to ask ANYONE with a sharp copy of this lense to trade with me, I would have zero takers.

Im just wondering if I should refuse to take it back from Canon now...

To be honest maxxed I reckon your stuck with it - and I use the word 'stuck' purposely. I've tried three 24-70mm and was disappointed with all of them. One was noticeably soft and although the other two very sharp, all three producing horrendous CA's - even at f8. I know I'm going to get jumped on from a very great height for saying this, but I think the 24-70mm f2.8 is a much over rated lens optically. In fact judging by the 24-105mm that's just arrived with my new 5D, I have a suspicion that it too is just playing on the fact that it's an 'L' lens. Are these two 'L' lenses simply hanging onto a reputation they gained with film because when it comes to digital they certainly don't perform for me - and that's in the real world.

Yes its still under warranty but they are 'fixing' it for free. In Hong Kong the Canon service is generally really excellent, and luckily I have only had to deal with them with regards to the 24-70. My others (85L, 35L, 70-200, etc) have all been rock solid and perfect for years.

I think what is happening here is they are giving me 'excuses' as to why the lense is not performing, and counting on my lack of knowledge of lense assembly to just accept what they are saying.

I guess I could always listen to that moron L. Valdemar in the other thread and sell my bodies and all lenses Good solution, that.

gofer wrote in post #4504855
To be honest maxxed I reckon your stuck with it - and I use the word 'stuck' purposely. I've tried three 24-70mm and was disappointed with all of them.

I was hoping not to hear that, but I feel a sense of relief that I'm not the only one. I am still going to try and get a replacement, but if not then I'll have to chalk it up to a poor purchasing decision and just move on. Its been 10 monts trying to get this to work well for me...

Look Maxxed, don't give up yet.

Wait until you get it back and try it, perhaps all will be fine. Take note of the testing suggestions I gave you earlier.

gofer wrote in post #4504855
...I've tried three 24-70mm and was disappointed with all of them. One was noticeably soft and although the other two very sharp, all three producing horrendous CA's - even at f8. I know I'm going to get jumped on from a very great height for saying this, but I think the 24-70mm f2.8 is a much over rated lens optically. In fact judging by the 24-105mm that's just arrived with my new 5D, I have a suspicion that it too is just playing on the fact that it's an 'L' lens. Are these two 'L' lenses simply hanging onto a reputation they gained with film because when it comes to digital they certainly don't perform for me - and that's in the real world.

I don't get it. I got mine brand new, and it worked as advertised from day one.

Seems to work for all these people, too: https://photography-on-the.net/forum/showthre​ad.php?t=173736