My 24-105L's sharpness test

wellman

OK, I know I might be about to lose the respect of a few people whom I respect. These are the people who say "don't measurebate; just shoot." Please understand that I am an engineer and therefore genetically predisposed to testing things, often for no good reason. I just can't help myself.

With that in mind, I ask you take a look and comment on the sharpness of my new baby, a 24-105L. I'm mostly looking for peace of mind, I suppose. I know that no one but me can decide whether I'm happy with a lens, but there are folks with orders of magnitude (see, told you I wan an engineer) more experience and perspective than me. Plus, this is the first time I've ever plunked down $1k for a lens, and the cheapskate in me says it better be good.

Linked below are side-by-side-by-side 100% crops at f/4, 5.6, and 8 for identical shots at 24, 50, and 105mm. All shots are ISO 100 and tripod-mounted, with the IS off. These shots are unsharpened and come from RAWs.

For some perspective on the effect of unsharpened images, I'm also including a sharpened/unsharpened combo image of my 85/1.8 at f/5 - the sharpest thing I have.

24mm: http://wellman.smugmug.com/photos/131872749-O.jpg
50mm: http://wellman.smugmug.com/photos/131872805-O.jpg
105mm: http://wellman.smugmug.com/photos/131872861-O.jpg
85/1.8 sharp/unsharp: http://wellman.smugmug.com/photos/131872933-O.jpg
Whole gallery, with originals: http://wellman.smugmug.com/gallery/2511531

So, please put my mind at ease or get me all tworked up - your call. And forgive me my inability to suppress that inner nerd. :wink

ziggy53

It looks like the f4 images could use some USM, but that's not unusual. There is still plenty of edge definition to make sharp images, not that these are far from the mark.

By f5.6, it looks like USM is not needed at all.

It does look like these were shot at fairly close range. I would be more interested in a more typical distance, and a slightly less contrasty subject.

I see nothing to get nervous about at this stage.

I test my own equipment also, just so I know what I have. I hate relying on what "others" say I have.

LiquidAir

What body is it on? The apparent sharpness of 100% crops depends on the pixel pitch of the sensor. I believe the 400D has the highest pixel pitch of any camera Canon sells. I have a 24-105, but the realtively low pixel pitch of my 5D makes it look very good.

As for putting your mind at ease, the results of your tests seem to match the Canon MTF charts pretty well. Reading the charts, at f/4 the 24-105 is sharpest at the wide end and gets softer as you zoom toward 105mm. As a result the improvment in sharpness as you stop down to f/8 is more pronounced at the long end. Your tests seem to indicate your lens behaves in a similar fashion to the design (Canon MTF charts are computer generated from simulations rather than measured).

When evaluating the sharpness of the 24-105 you have to remember it has a greater than 4x zoom range. It does exceptionally well for a lens with such a wide range, but it still is going to be outclassed by primes at the wide end of its aperture range. Every prime I own outresolves the 5D sensor at f/4.

From a practical stand point, I would not worry too much about the degree of softness you are seeing there. Even the softest of the shots you are showing there will print just fine fairly large.

pathfinder

I agree that good primes are better than zooms. That does not mean, however, that the 24-105 won't give superbly sharp images.

This image was shot with a 24-105 L at f8, 8/10th secs, on a tripod at 24 mm, with a 1DsMkll in Antelope Canyon

In large prints, you can see the individual grains of sand falling in the light shaft in the upper half of the image.

TristanP

Pathfinder, that shot is spectacular. So spectacular, I actually bought a 10x15 of it.

pathfinder

Tristan,

Thank You. That was one of my favorites from last spring in Utah also.

I suspect that is my first ever sale!

What did it cost? Let me know what you think of it when it arrives too, please!!

wellman

Thanks to everyone for your comments. And pathfinder, that photo is beautiful! Did I see that one in the DGrin POTY contest?

At Ziggy's suggestion, I took a more "everyday" series of shots. I set the tripod up on the deck and took photos of the neighbor's roof. I also sharpened these my "dummy" amount, 40 in Adobe Lightroom. I think these show that in everyday use, f/4 is very good. These shots start here.

One thing did surprise me... Just for the heck of it, I removed my B+W UV/haze filter (multi-coated) for a test shot at 105mm and f/4. I wanted to see if the filter was causing any degradation. What I found was that the filter appears to help control CA (or is it PF). Here's a side-by-side. Has anyone else seen this behavior?

Enjoy the last of the weekend.

TristanP

pathfinder wrote:

Tristan,

Thank You. That was one of my favorites from last spring in Utah also.

I suspect that is my first ever sale!

What did it cost? Let me kow what you think of it when it arrives too, please!!

$6.49 in Lustre (default pricing). I printed one of my own a while back from my DC trip for my Mom in that same size, matted and framed in a 16x20, and it came out great. I'm sure this one will be spectacular on my wall.