Very interesting little comparison Lak...
Even more interesting because I just got the EF-S 17-85 IS, which is generally considered to be the "1.6 crop factor equivalent" of the 28-135 you have.
I've been curious about comparing the images of the 17-85 to the 28-135, as I expect the good and bad points to be a little different for each lens. It seems a lot of the people who's opinions I've read in various places (not here) think that just because the 28-135 displays a certain characteristic then the 17-85 will have the same one. I would be very suprised if this were true. For example, I'd be suprised if the 28-135 has anywhere near as much barrel distortion as the 17-85 when used at its shortest focal length.
Anyway, seeing your comparison with the 18-55 kit lens and the 50mm f/1.8 prime prompted me to do my own little comparison... seeing as I have both of these lenses to compare against too. I was a bit suprised at how soft your kit lens was at f/5.6.. so I wanted to replicate your test as closely as I could to see the difference.
I know that you would have used "version I" of the kit lens while I used "version II", but supposedly they are optically identical. I also used a 350D instead of a 300D, but I don't expect that to have much impact on the test (which isn't that scientific to begin with).
The first results here are trying to replicate your test.. high contrast red/white text smack in the middle of the image at 50mm focal length and a few feet away. I even used my desk with monitor behind it (
) but my desk is messier than yours
Camera was mounted on a tripod and I used a remote shutter release (but didn't bother with mirror lockup).
Here are the results... note that I took all shots in RAW and then converted them using Adobe Camera RAW with the sharpness and noise reduction set at zero... so they have no in-camera sharpening or PC sharpening applied to them at all.
First up, 50mm prime lens at f/5.6 and then f/8.0:
[Image: Crop_IMG_3418.jpg][Image: Crop_IMG_3419.jpg]
Next, 17-85mm at f/5.6 and f/8.0:
[Image: Crop_IMG_3421.jpg][Image: Crop_IMG_3422.jpg]
And finally the 18-55 kit lens at f/5.6 and f/8.0:
[Image: Crop_IMG_3423.jpg][Image: Crop_IMG_3424.jpg]
As you can see, all images are a bit softer than yours (I suspect you didn't turn all sharpening off, because when sharpening was set to default levels they came out very similar to yours).... but.. yeah I think its fair to say my kit lens is just as bad as yours! And while the 50mm prime wins convincingly, the 17-85 appears closer to the 50mm prime quality than the kit lens quality perhaps.
But like Adam, I was curious about the results in the corners too, which is where the kit lens really falls apart I find.
So I set up another test with contrasty detail in the corners and everything on the same focal plane (using the bottom middle focus point to focus on some black text on the grey box), and then used the same lenses to basically do the same test as before.
Here is the overall shot:
And here is the bottom-left corner using the 50mm prime at f/5.6 and f/8:
[Image: BottomLeft_IMG_3433.jpg][Image: BottomLeft_IMG_3434.jpg]
The same crop with the 17-85 lens at f/5.6 and f/8:
[Image: BottomLeft_IMG_3431.jpg][Image: BottomLeft_IMG_3432.jpg]
And the 18-55 kit lens:
[Image: BottomLeft_IMG_3426.jpg][Image: BottomLeft_IMG_3427.jpg]
A huge difference. While the 50mm prime and 17-85 hold together nicely at the edges (the 50mm still way better), the kit lens turns to slush. Strangely, the f/8 result seems even blurrier than the f/5.6 result. I quick comparison of 100% crops of the part of the image I was focussing on shows that the problem seems to be that the kit lens simply didn't focus correctly. If this is the case, it simply highlights the better focussing of the other lenses, or perhaps that the camera struggles to focus through the edges of the kit lens (which I suspect to be the case - often the kit lens seems to only lock focus when using the centre focus point).
Here are 100% crops of the area where the camera was (supposed to be) focussing on:
50mm prime at f/5.6 and f/8:
[Image: BottomFocusPoint_IMG_3433.jpg][Image: BottomFocusPoint_IMG_3434.jpg]
17-85 at f/5.6 and f/8:
[Image: BottomFocusPoint_IMG_3431.jpg][Image: BottomFocusPoint_IMG_3432.jpg]
18-55 kit lens at f/5.6 and f/8:
[Image: BottomFocusPoint_IMG_3426.jpg][Image: BottomFocusPoint_IMG_3427.jpg]
Sorry Lak, I didn't mean to hiijack this thread.. but I thought your results said as much about the kit lens and 50mm f/1.8 as they did about your 28-135... and I also thought my 17-85 was a very relevent comparison to the 18-135 because it is marketed as a "digital equivalent" to your lens.
Either way, you must be very happy with your lens as it obviously performs like it should... I saw it advertised in the Quokka, and know you got it at an absolute steal.
ps: I notice you just included edge crops.. yaay.