First let me say I think the new site is a vast improvemnt over the old and I for one will be renewing my subscription to the LL video journal which pays for this site.
As Jonathan Wienke frequently mentioned, there's no free lunch, and I don't expect to use valuable bandwidth on someone elses site for free.
The facility of now being able to download images directly from one's HD is a major upgrade which is most welcome.
With this in mind, I'm hoping to demonstrate a curious phenomenon which basically knocked my socks off.
Most of us are not scientists, and even if we were we'd have a difficult time making sense of all the contradictory data regarding lens performance, due to lack of reliable, up to date information in the public domain.
I recently bought a Canon 5D and the 24-105mm zoom lens, which I believe is a great combination. During the past 6 weeks or so, I've taken about 4,000 images in Nepal, Tailand and Cambodia using mostly the 24-105 lens, but occasionally the Sigma 15-30.
I'm now processing these images and in the process of doing so I noticed that images I'd taken at f16 were no less sharp than the same image taken at f11, in any respect, but the f16 image exhibited greater DoF.
This actually flies in the face of common understanding that f16 is softer than f11 and f11 is very slightly softer than f8.
The following images demonstrate that this is not necessarily true.
The image that brought this to my attention was a shot of the Bayon temple near Angkor Wat. I took 2 shots, one at f11 and one at f16. The shutter speed was the same (100th) in both instances (which of course meant I bumped up the ISO to 200 for the f16 shot).
Examining these 2 shots of the same scene, having focussed on the same spot in each exposure (guesstimating the hyperfocal distance as I always do), I find the f16 shot is sharper in all respects. Geez! That can't be right! What have I done! F16 sharper than f11, or at worst equally sharp!!!
So here's the proof. I should also add that the following images have had zero sharpening and zero luminance smoothing, I've also adjusted the shadows and contrast sliders to ensure no clipping of highlights and shadows. These are not images adjusted for printing, and as a matter of fact my monitor is not even calibrated because my system is 64 bit (the calibration people are seriously lagging behind technological developments) .
Here's the overview.
Here's the foreground showing a portion of the Lion's mane (sorry for another cat shot). It's a bit blurry.
Now here's the foreground of exactly the same shot but taken at f16 and ISO 200 to maintain shutter speed of 100th.
You should be able to see that it's noticeably sharper and that shooting at f16 has had its advantages. But what about the background? Well here's the background at f11 and f16.
If you examine these images you'll see that the f16 images are sharper. The f16 foreground image is quite noticeably sharper. The f16 background image is marginally sharper.
So what! I hear you say. That's what you'd expect. And yes it is. But what you'd also expect is that at some point in between the nearest point and the furthest point the f11 shot would be sharper. You have to believe me on this, it isn't.
There's no point anywhere on the f11 shot that is as sharp or sharper than the f16 shot.
Conclusion? This lens (at 85mm, did I forget to mention that) is sharpest at f16. Now that's good news because there are 2 interesting ramifications. (1) I can use f16 with impunity without agonising over any trade-off in resolution, (2) The 5D sensor (and the 1Ds before it) is really not as good as some of the lenses attached.
For those of you who are skeptical, who think maybe I am suffering from Parkinson's or dipsomaniacal tremors, I put my camera on a tripod indoors; used remote control and mirror lock-up, and produced the following results.
Essentially, maximum resolution of the 24-105 lens at 85mm is the same across f8 to f16. What differs is the DoF. I haven't wasted bandwidth by showing this. It's too obvious.
I should qualify the above statement. Maximum resolution of the 25-105/5D system is the same across f8 to f16 at 85mm. I can only speculate on the reasons. My guess is that the 5D pixel size is too big to delineate (differentiate whatever) anything smaller than the f16 Airy disc. Please feel free to dispute this.
Okay! The images are too small. They are in fact around 100th of the area of the full image. If you need to see them, I can provide bigger images. Maybe I confused centimetres with inches in PS.
Yep! PS on my 64 bit system was set to cms instead of inches. Sorry about that, but I don't expect there'll be any clamour for larger images, but I do wish you Americans would get in line with the rest of the world .