Soft image from 70-200 f4 IS

A couple of things -

1. Be prepared to shoot using the aperture in the F-8 or so range.  This is just a matter of fact with most zoom lenses.  Leave the shutter speed and ISO set to automatic.  Try it it works..!

2. I own three "L" lenses.  They are ALL soft when mounted to an APS-C (small sensor) camera.  BUT...they all three work VERY nicely, sharpness wise, when mounted to my full frame (larger sensor) 6D.  Like two different lenses.  I bought a 28-300L lens and was very disappointed with the lens as mounted to my...SL1, my 40D and my 50D bodies.  But when I bought the 6D...it and my other two "L" lenses magically got remarkably sharp.  Still not "prime" lens sharp, but MUCH better than when mounted to the small sensor cameras.

Mike

Mike wrote:

A couple of things -

1. Be prepared to shoot using the aperture in the F-8 or so range. This is just a matter of fact with most zoom lenses. Leave the shutter speed and ISO set to automatic. Try it it works..!

No, the 70-200/4L IS is sharp at f/4. We're not talking about a consumer grade zoom here.

Auto ISO is also a bad suggestion for testing, because the additional noise of a higher ISO speed takes the edge off sharpness and also reduces contrast which has an effect on subjective sharpness. Set a low ISO speed and test in good light so the shutter speed will be high enough. Ideally use a tripod unless you are very confident that there is no camera shake, and choose a static subject, not one which is fluttering in the wind for example.

2. I own three "L" lenses. They are ALL soft when mounted to an APS-C (small sensor) camera. BUT...they all three work VERY nicely, sharpness wise, when mounted to my full frame (larger sensor) 6D. Like two different lenses. I bought a 28-300L lens and was very disappointed with the lens as mounted to my...SL1, my 40D and my 50D bodies. But when I bought the 6D...it and my other two "L" lenses magically got remarkably sharp. Still not "prime" lens sharp, but MUCH better than when mounted to the small sensor cameras.

I have several Ls (including as it happens the 70-200/4L IS, but also other primes and zooms), used exclusively on crop cameras and they are perfectly sharp.

This is in principle an outstandingly sharp lens under almost all circumstances, although it is a bit weak at 200mm MFD. All the reviews that I have seen agree on this, and it has certainly been my own experience with my copy. However, my son bought one s/h that was disappointing, but Canon at Elstree (UK) sorted it out and it is now fine – we think there may have been an internal misalignment.

So, the fist thing to do is to test your lens properly – apart from anything else, DoF issues make it hard to draw any conclusions from the images you have posted. Use Live View to obtain accurate focus on a detailed flat subject perpendicular to the lens axis, like a building with plenty of fine architectural features. That will tell you whether the problem is with your lens. If it is, send it to Canon in the hope that they can sort it out.

This thread is the only issue I've heard of with that lens.

For what it's worth I've got the same lens and a 450D, and it is sharp even at f4.  So either there's something you were doing (eg handheld with IS off), or there's maybe something up with your lens.

As others have said, perhaps try some more scientific test shots.

Mike wrote:

A couple of things -

1. Be prepared to shoot using the aperture in the F-8 or so range. This is just a matter of fact with most zoom lenses. Leave the shutter speed and ISO set to automatic. Try it it works..!

2. I own three "L" lenses. They are ALL soft when mounted to an APS-C (small sensor) camera. BUT...they all three work VERY nicely, sharpness wise, when mounted to my full frame (larger sensor) 6D

Its not the senor size that affects the sharpness but the size of the pixels. For instance the 5Ds has very small pixels too.

. Like two different lenses. I bought a 28-300L lens and was very disappointed with the lens as mounted to my...SL1, my 40D and my 50D bodies. But when I bought the 6D...it and my other two "L" lenses magically got remarkably sharp. Still not "prime" lens sharp, but MUCH better than when mounted to the small sensor cameras.

Mike

Mike - wrote:

Sorry, my answer stands..!

This is from real world use of various cameras and lenses. NOT JUST....TESTING. Actually taking photos...then...checking what you have. Again, not just taking pictures of a piece of news print on a wall...I'm talking "real" photos..!

As was my comment about the 70-200 f4 IS being sharp on my 450D. I've never "tested" it; I just use it and love using it.

An "L" lens on an APS-C body WILL NOT...provide the best that it can on a full frame body...period. Same goes for Nikons I've got.

It won't provide the best that that lens can; the same lens on a full frame body would be sharper. But I don't have a full frame body...

But, I'm not aware of an EF-S zoom with a similar range that's as sharp, let alone any sharper. And even if there is, I love the build and feel of my 70-200 and it's plenty sharp enough for me.

When using APS-C cameras, stick with the non-L lenses, you get sharper pictures...if that's what you are looking for. Many like the softer image...and that's fine, I don't

So what lens should I be using in your opinion?

Mike wrote:

1. I own three "L" lenses. They are ALL soft when mounted to an APS-C (small sensor) camera. BUT...they all three work VERY nicely, sharpness wise, when mounted to my full frame (larger sensor) 6D.

It is a given that the maximum 100% view pixel sharpness with the same lens and f-number will be higher with bigger pixels with the same relative AA filter strength. All lenses are very, very soft with small enough pixels, as it should be.

In this case, however, the OP's camera has a pixel size that is very close to that of the 6D. I have an APS-C camera that has pixels much larger than those in the 6D.

Mike - wrote:

When using APS-C cameras, stick with the non-L lenses, you get sharper pictures...if that's what you are looking for. Many like the softer image...and that's fine, I don't.

Mike

Uh, I believe that this statement is incorrect.  You might get "more sharpness per dollar spent", but typically the L lenses are more sharp than non-L lenses (not in all cases, but typically).