Canon 24-105 f/4 L

I'm sure this has been discussed before (but I can't really find where) but a lot of discussion focuses on 'this lens is really sharp, this lens is a bit soft etc' and my question is - how do you judge if a lens is sharp or not ?

The reason I ask, is that to my way of thinking, there are just so many ways to judge sharpness......and RAW files straight out of a camera (in my case, a 40D) are soft by nature (isn't this inherent in digital photography ?) and discounting technique etc (ie too slow a shutter speed, f stop etc) so to really judge how sharp an lens/image is, surely some amount of PP must be done (DPP, Photoshop etc) so any assessment of sharpness surely is then subjective from that point on ?

The reason I ask this is that I've just bought a Canon 24-105 f/4L to replace a canon 28-135 and have been less than impressed with the sharpness of the 24-105, and I'm really struggling to see much difference to the 28-135 in this area.

I've seen a lot of posts about how sharp this lens is, but how 'sharp is sharp' and hence my question above

Corner sharpness, sharpness at the extremes of the focal length, etc should all be better than the 28-135 IS.

It should be sharp more consistently.

Is your 24-105 soft, or just not much sharper than your 28-135. From what I understand, the 28-135 is a decent lens, so perhaps there isn't much of a difference. And I would say that stopped down a bit the sharpness would be indistinguishable.

Try posting some samples up.

timnosenzo wrote in post #5248608
Is your 24-105 soft, or just not much sharper than your 28-135. From what I understand, the 28-135 is a decent lens, so perhaps there isn't much of a difference. And I would say that stopped down a bit the sharpness would be indistinguishable.

Try posting some samples up.

I think that's probably the case, as the 24-105 is my first L lens and I probably expected more and that I'm struggling to pick much, if any, difference in 'sharpness'...........​.the difference between expectation and reality I guess

DDWD10 wrote in post #5248395
Corner sharpness, sharpness at the extremes of the focal length, etc should all be better than the 28-135 IS.

It should be sharp more consistently.

Good point about corner sharpness, but at 105 mm there is a noticeable reduction than say at 70 mm

The new lens should offer more than just sharpness - colour and contrast should be better too.

CB357 wrote in post #5249845
I think that's probably the case, as the 24-105 is my first L lens and I probably expected more and that I'm struggling to pick much, if any, difference in 'sharpness'...........​.the difference between expectation and reality I guess

There is definately something in that. I have owned around 14 l's and few have blown my socks off compared to other decent lenses. They have good build and USM tho' and that adds value to me. but this is a great lens and definately a step up from the feeble 28-135mm IMO, having owned both. Post a shot and should be easy to judge. I want my lenses sharp wide open and with minimal sharpening and other PP applied to achieve that. If you expose the shot well then they should be clearly sharp with good colour and contrast. Lesser lenses tend to need more PP work to get anywhere close.

I have a 40D and upgraded just as you a few months back. Playing with my 24-105, I found it to be best about f/8 - f/11. It is definitely better than my 28-135, but it is not day and night. Your expectations (as mine) may have been too high. What a price difference in the two. As mentioned above, the color contrast is something I noticed to be improved. Maybe you have not shot subjects that allowed that to show yet. Another thing, it is not as sharp in the 24-35 or 90-105 range in my opinion. Find a good subject with detail and color in it and shoot at f/11 or so in the middle of the focal range. I would be surprised if you could not see a difference in the two lenses. With that being said, the 28-135 is a better lens than I thought it was. Perhaps you are in the same boat. Rather than thinking the 24-105 is bad, perhaps the 28=135 is just better than we thought. I don't regret the upgrade at all though. It is a great lens with much better build quality than the one it replaced. I would test your lens further to be sure it is not a "soft" copy.

Thanks to all you guys, your opinions and feedback have been great - from what I'm gathering here is that the 24-105 is a very good lens, the 28-135 wasn't all that 'bad' and that I need to 'grow' with the 24-105 (after all, it's an L lens )

I really appreciate the feedback and advice - thanks again