Canon 20D 17-85 IS and Sharpening

[kdoc]

My new 20D 17-85IS seemed to come out fairly (disappointingly) soft--no other in camera settings of note. Then I noticed that if I boosted the ACR sharpening (preview only, 100% size!!!) up from 25 to 50 or even 75, things looked pretty good (so far--very preliminary, but leaving town in 36 hours, so in a hurry--no prints as of yet with my 2200). So I'm wondering whether I've got a camera-lens problem, or just a sharpening one. When I used the standard PK capture sharpen (this time High Res, Narrow), and then the output sharpen for inkjet, it came out pretty good again--on screen...but didn't look oversharpened as is sometimes the case on screen). What's your experience, and how would you sharpen this camera-lens combo?

Thanks

kdoc

[Bruce Fraser]

I've been shooting the 20D 17-85IS combo for about three months. My other lens is the 28-300 IS. With either one, captures processed through ACR with no sharpening are indeed quite soft, but they sharpen up very nicely.

I suspect that the antialiasing filter on the 20D is a tad more aggressive than on other Canon cameras. I've been experimenting with simply running AutoLevels on the layer masks after using High-Res Capture Sharpen Expert, and thus far I haven't seen any ill effects from doing so.

I think it's fair to say that the 20D is at the soft end of the scale (with something like the Kodak 14n being at the sharp end). That doesn't mean I'd consider for an instant trading my 20D for a 14n! But you can probably hit 20D files with sharpening harder than you can most other cameras.

I don't think it's a lens issue.

[jlipkin@ramapo.edu]

Kdoc --

I had the same problem with the 17-85 lens that came with my 20D. It didn't seem any sharper than the 20-35 f/3.5-5.6 that I had been using with the digital rebel. I fixed the problem by returning the lens and replacing it with a 17-40 f/4L. A bit more money, but a really fantastic lens.

Jonathan

[kdoc]

Thank you. (I've been away, hence the delay): Two Questions re this:

1. I haven't been using High Res Capture Sharpen Expert: would you mind explaining in a little detail how you use it, and how you do so with the Levels Auto--do you just highlight both layer masks and then run Image--Adjust--Auto Levels...and leave the opacities as is?

2. This is a bit mucho f a question, bordering on photography 102 or 103, but I find I'm confused on the distinction between a. an image in focus which needs sharpening, b. one which is slightly out of focus (obviously one difference is that the former will sharpen up)...and c. an image taken with an inferior lens which is in focus, not so sharp, and doesn't really sharpen up. What exactly do we need to understand among these three possibilities.

As always, thanks.

kdoc

[Mark D]

My experience and understanding re question 2 is this: one needs to distinguish between images that are out of focus and images that need their acutance improved. If my theoretical memory serves me right, images that are out of focus have what are known as "circles of confusion" because the focal distance between the lens and the film plane or sensor is incorrect relative to the subject-to-lens distance. "Sharpening" with USM or PK Sharpener can make some difference to these images but not really cure a focus problem. My experience with PK sharpener indicates that the DOF brush is the best it gets in remedying this problem, but cannot really sharpen severe out-of-focus cases. The acutance issue, on the other hand occurs, for example, where an anti-aliasing filter placed in front of the sensor slightly diminishes edge contrast giving an otherwise well-focused picture a bit of a fuzzy appearance. PK Sharpener cures this problem superbly.

There is a third possibility of poor quality optics simply producing somewhat blurry images.

I think one could partially analyse the problem empirically - i.e. make carefully controlled focus tests with the camera on a tripod, to be sure that your problem is not hand-shake, (because IS can only compensate so much). In Photoshop use PK Sharpener Expert High Res Capture sharpen, no other gadgets, then use PK Output sharpener corresponding with the PPI in the file and print it. If the print is fuzzy, then you probably do not have an acutance problem (because PK used in the manner described should normally deal with it), but you may well have a lens/camera combination that is not focusing properly or has other optical issues causing blurriness. I think that is how I would go about trying to differentiate between acutance and optical issues.

[kdoc]

Thank you. I'm more trying to understand this on a theoretical level, than worrying about my camera-lens, though perhaps I should do so more. And this answer is a good beginning. I'm going to have to review acutance a little more. :). Can you and Bruce say more about why the "Expert" Sharpener, and to what degree you tweak the preset results, either running that Auto Levels, changing the opacity, or whatever. For this capture sharpening do you merely look on the monitor to judge the "adequacy" of the sharpening? I haven't had much of a feel for deciding to what degree to do these tweakings or even how to decide (workflow wise) when to bother.

kdoc

[Mark D]

It is best for Bruce to answer this. He developed it, I am just a user. However, for what it is worth, based on my experience as user, with my Canon 1Ds and either the 28-135 IS USM lens (an average Canon lens - nothing special), or the 70-300 IS USM DO lens (an above average Canon lens), I generally find I do not need to tweak anything at the Capture Sharpen level. Normally I just run it at its default settings, flatten the image and proceed with the rest of my processing. If the image still looks as if it needs some sharpening, I use one of the "Creative sharpeners", but gingerly, because they are quite powerful and there is still Output Sharpening at the end of everything. We need to take care that the print comes out not looking over-sharpened. There is a bit of trial and error required here because monitor resolution just doesn't quite allow WYSIWYG treatment of sharpening.

[kdoc]

Hi again Bruce: Can you please tell me your settings when you run auto-levels on the layer masks in Expert Hi Res Capture Sharpen? Where do you set your clipping points? And in general, for using these autos, as an adjustment layer, with options, where do you set your clipping points, or do you vary them?

kdoc

[Bruce Fraser]

For automated use with the 20D /75-85 IS, I simply select the layer masks and run Autolevels at the default setting, which is 0.50% clip for both black and white. I built a simple action that cals PK Sharpener, applies the sharpening, then tweaks the layer masks automatically (This also seems to work quite well on the 1DsMkII, at least when using ACR as the raw converter.) If you're willing to do handwork, you can of course make much more nuanced adjustments.

Basically, increasing the black clip protects more pixels, increasing the white clip sharpens more pixels, and tweaking the gray slider adjusts the contrast of the mask and hence the transition between sharpened and unsharpened areas.

I can't really tell you what to look for because monitors vary so wildly in the way they show sharpening (and even the same monitor can look very different when you change the resolution)?it's something you simply have to develop a feel for based on your own display(s).

I've just about got the relationship between what the Artisan shows and what the EIZO ColorEdge shows nailed down, but it took me quite a while to do so.

[kdoc]

Thanks very much.

kdoc

[zizzy]

After having soft focus problems with a brand new 20D with 17-85mm IS lens, I did a bunch of online research and performed my own focus calibration tests that the camera. I concluded that the camera had a front-focus problem. I sent the camera to Canon. They replaced focus screen, adjusted the film plane calibration, and checked the calibration of the lens. The camera is much better now.