Canon EF 24-70mm f/4L IS Resolution Tests!
/forum/topic/1178996/9

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thw2
Registered: Dec 27, 2004
Total Posts: 2828
Country: N/A

alundeb wrote:
The sample crops from TDP suggest that the performance at 50 mm (center of image) is worse than all other zoom lenses, including cheap ones, and that it does not improve substantially by stopping down, and that the copy variation is significant.


Indeed. Even when stopped down to f/8, performance of 24-70 f/4 lens at 50 mm remains poor, BOTH at the center and in the corners. Now, that is disturbing. If the lens performs well at 50 mm when stopped down, I will have no problem with it.



alundeb
Registered: Nov 06, 2005
Total Posts: 4243
Country: Norway

gdanmitchell wrote:
Not sure if you are referring to my post or to something else, but since I responded a bit negatively to the new "bad at 50mm" business I'll reply a bit.

The familiar "you haven't used the lens" criticism is useful as far as it goes, but at this point few of us have extensively used all three of the current 24mm-(more than 24mm) Canon L options. I have not used it yet, and I don't think I made any claims to have concrete personal experience with the 24-70mm f/4. I think I kept my comments in the realm of things that a person could reasonably observe both about the specific lens and about the general question of how lens performance is evaluated - at least that was my intent.

It is reasonable and possible to have something useful to say about a lens performance discussion from that perspective - though I'll freely acknowledge that long and intense use of a lens can inform one's opinion in other useful ways. (I have that experience with the 24-105, and I now also have some experience with the f/2.8 24-70 II.) My comments were more about how we judge lenses than about the specific performance of the f/4 24-70.

My points were basically two:

1. Forum discussions often seem to morph the observation that a good thing is best in condition A into an assumption that it must therefore be bad in condition B. I think that something like that may be happening here with the f/4 24-70 lens, where there doesn't seem to be much evidence that the lens performs in a manner that could objectively be described as "poor" at 50mm but just that this isn't its best FL. The real question isn't whether it is better or worse at 24mm, 50mm, or 70mm, but rather how it performs as a photographic tool for our purposes. We can say something similar about almost any zoom lens - I have yet to meet a high quality zoom that performs equally well at all focal lengths and apertures.

2. When comparing things like lenses, forum discussions (and similar comparisons) often can lead towards a false and simplistic assumption that one thing is "best" and that other things are "deficient" - e.g. we try to pick a winner and losers. My point is that there are so many factors in play - the photographer's specific needs, functionality, etc. - that this can be a false way to evaluate gear. In many, many cases we are actually comparing a number of things that are quite good. I believe that is almost certainly the case here, based on my actual experience with the 24-105 and the 24-70 f/2.8 II and on reading a lot of evaluations and commentary on a lot of lenses.

I went back to the original link that started this thread to see what the author actually said about the 50mm performance. Here is a quote:

"We did find that 50mm resolution was slightly lower than 70mm for every copy. The center / weighted average at 50mm for the 24-70 f/4 IS was 875 / 700, compared to 920 / 750 at 70mm. Not a huge drop, but it was consistent. This is a bit surprising, but not a total shock. Some wide angle zooms exhibit similar behavior and the dip in resolution isnít extreme."

(Emphasis added to original text.)

That is in line with the point I was trying to make. I hope this clarifies things a bit.

Take care,

Dan

(edited after original post)


My post was referring to yours among others.

My question is simply, on what basis are you ignoring one side of conflicting information from different credible sources? Mind you, that as far as I know, Roger Cicala has only made measurements at f/4, and he has only presented and commented about numbers, not visual comparisons.

Or are you saying that this is "above decent" performance for a 50 mm lens at f/8?

http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=823&Camera=453&Sample=0&FLI=2&API=3&LensComp=116&CameraComp=453&SampleComp=0&FLIComp=2&APIComp=3



twistedlim
Registered: Oct 20, 2004
Total Posts: 3127
Country: United States

Ok went out in the cold for you guys and took some shots comparing the 24-70 f4 IS at 50 mm (the supposed weak spot) against the 50 1.4. Shooting both at 4.0 they are pretty much what you would expect. Centers are close but the prime is far ahead on the corners (as it should be since it it stopped down quite a bit). At f8 the differences were harder to detect. I am not going to post a blind comparison. The pbase link will show you the 24-70 f4 at f8 compared to the 50 1.4 at f8. I see very little real world differnce and would have no issues with shooting this lens at this focal length. Yea there could be sample variation...bla bla bla but I think I have a good copy of the 50 1.4 and and pleased with the 24-70 f4. Take a look and decide. These are full rez jpegs converted from raw files in DPP. The camera settiings were what I usuallly use. Neutral color, sharpness 4, contrast and saturation at +1. Link below:

http://www.pbase.com/twistedlim/test2470

**PS I have now added the f4 shots from both lens.



gdanmitchell
Registered: Jun 28, 2009
Total Posts: 9179
Country: United States

alundeb wrote:
My post was referring to yours among others.

My question is simply, on what basis are you ignoring one side of conflicting information from different credible sources?...

Or are you saying that this is "above decent" performance for a 50 mm lens at f/8?


Your "question" is an odd one. It reminds me a bit of the famous question: "Is it true that you are no longer beating your wife?" You begin with a presumption that I'm ignoring something willfully and that I have a basis for doing so. But the fundamental question is a non sequitur that doesn't logically follow anything I wrote about.

My post said what my post said. I'm not "ignoring" anything and I'm not specifically characterizing the performance for this lens at f/8 and 50mm in any specific way. Precisely contrary to that, I am urging a bit of caution and reflection before others jump to rather negative and quite possibly overblown conclusions about this lens.

I'm confused as to how or why you interpreted my post in these ways.

Take care,

Dan



alundeb
Registered: Nov 06, 2005
Total Posts: 4243
Country: Norway

gdanmitchell wrote:
I am urging a bit of caution and reflection before others jump to rather negative and quite possibly overblown conclusions about this lens.



Similarly, I am urging a bit of caution before characterizations like "sillyness" are thrown out when someone is questioning the performance of a new lens after some bad reports have arrived.



gdanmitchell
Registered: Jun 28, 2009
Total Posts: 9179
Country: United States

alundeb wrote:
gdanmitchell wrote:
I am urging a bit of caution and reflection before others jump to rather negative and quite possibly overblown conclusions about this lens.



Similarly, I am urging a bit of caution before characterizations like "sillyness" are thrown out when someone is questioning the performance of a new lens after some bad reports have arrived.


Aside from my word choice, then perhaps we are more or less on the same page when it comes to caution about snap judgments regarding this lens? ;-)

Dan



thw2
Registered: Dec 27, 2004
Total Posts: 2828
Country: N/A

twistedlim wrote:
Ok went out in the cold for you guys and took some shots comparing the 24-70 f4 IS at 50 mm (the supposed weak spot) against the 50 1.4. Shooting both at 4.0 they are pretty much what you would expect. Centers are close but the prime is far ahead on the corners (as it should be since it it stopped down quite a bit). At f8 the differences were harder to detect


Thanks. Very much appreciated.

At f8, your 50 f/1.4 appears sharp on the extreme left corner and soft on the extreme right corner while your 24-70 f/4 exhibits the opposite behavior. Both are the same at the center.

It's disturbing the 24-70 f/4 is showing such wild copy to copy variation.



twistedlim
Registered: Oct 20, 2004
Total Posts: 3127
Country: United States

I am really happy with the new 24-70. Hopefully it will be in my bag more than the old 2.8. I hardly shoot zooms anymore but then again I do not shoot events anymore either. I am just shooting for the fun of it now.
Funny when I look at them I see the opposite. In any case I tried to get bricks in across the frame. Bricks can really get mushy on a soft lens. Both of these at F8 are more than acceptable and better than any 17-40 or 24-105 I have shot.



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