Strange bokeh?

codrus · March 11, 2011

Is it just me, or do the bokeh in this shot look strange? It almost looks like motion blur, but the rest of the image is sharp. I shot it with my 50D and 70-200 2.8 IS (original), at 200mm and f/2.8. Just a moire pattern from the grid on the towel, perhaps?

--Ian

r3t1awr3yd · March 11, 2011

That's the craziest bokeh I've ever seen. Nifty.

ian408 · March 11, 2011

Looks like the fabric is either a ripstop material (larger threads look like squares)--maybe surgical towel or something similar?

ziggy53 · March 11, 2011

On an old CRT monitor I see some patterning moiré but not color moiré. I suspect that those on LCD displays are seeing some color moiré. (This is a good thing and I will explain later.)

Yes, I believe that is caused by the particular fabric weave pattern and because it is such a pure blue. Remember that blue occupies around 25% of the photosites in a Bayer imager. (There are twice the number of green photosites as either red or blue and the arrangement is generally R-G-B-G.) This is part of the reason why pure blue skies can sometimes show grain especially when you apply sharpening.

(For more information about Bayer sensor design:)

Partly too I suspect it is the image sharpening option that you set within your SmugMug account gallery setting for reduced sized images, i.e. this XL sized image probably has some simple USM sharpening applied from your SmugMug settings.

Did you apply any sharpening to the original image in post-processing?

If you think this patterning is too much competition and/or distraction from your intended subject I suggest using Photoshop (or similar), selecting the blue region and using some blur against the region. It would be best to do this against another, higher layer since blurring the blue will probably affect some of the fur detail, which you may wish to reveal manually.

BTW the reason I said that I see patterning but not color moiré is because with color moiré you will get unsightly color patterns which I don't see in this image. Color moiré is more difficult to correct.

codrus · March 11, 2011

ziggy53 wrote: »

On an old CRT monitor I see some patterning moiré but not color moiré. I suspect that those on LCD displays are seeing some color moiré. (This is a good thing and I will explain later.)

...

Partly too I suspect it is the image sharpening option that you set within your SmugMug account gallery setting for reduced sized images, i.e. this XL sized image probably has some simple USM sharpening applied from your SmugMug settings.

Did you apply any sharpening to the original image in post-processing?

Yes, I'm looking at it on LCD. I do have an old CRT sitting in the corner that I might hook up to see the difference.

I'm using the default smugmug sharpening settings -- reading up on them now. Looking at the original photo (either on SM or in Aperture) doesn't show the same effect, so I think you're right about it being brought out by the sharpening algorithm.

Aperture applied some sharpening to the original during RAW conversion by default as well, but turning it off doesn't seem to affect effect significantly.

thanks!
--Ian

borrowlenses.com · March 11, 2011

Yep, it's strange. Almost looks like you captured the Steve Jobs reality distortion field.

Overfocused · March 11, 2011

If you look at it in the original size picture and compare it, I think it's from downsizing and not the actual picture. There are patterns but not that apparent or even close to looking like moire.

codrus · March 11, 2011

borrowlenses.com wrote: »

Yep, it's strange. Almost looks like you captured the Steve Jobs reality distortion field.

Heh. I *was* using Aperture on my iMac, but last I checked Steve Jobs wasn't as cute as a baby cheetah!

--Ian

WinsomeWorks · March 12, 2011

I see lots of weird artifacting all over the photo, not just in the blue fabric. If I look at the image in original size, it's got odd stuff everywhere. Lots of the fur has all kinds of weird stuff. If it was shot at 800 ISO (that's what the info. says), and had exposure brightened up, then had sharpening like you've described, I think that would explain it. However, if it wasn't brightened at all, then it seems unusual. Looking at the shot of the cheetah in that same gallery at original size though, some of the same is present (not nearly to that extent). But the cheetah shot was only 400 ISO.

codrus · March 12, 2011

WinsomeWorks wrote: »

I see lots of weird artifacting all over the photo, not just in the blue fabric. If I look at the image in original size, it's got odd stuff everywhere. Lots of the fur has all kinds of weird stuff. If it was shot at 800 ISO (that's what the info. says), and had exposure brightened up, then had sharpening like you've described, I think that would explain it. However, if it wasn't brightened at all, then it seems unusual. Looking at the shot of the cheetah in that same gallery at original size though, some of the same is present (not nearly to that extent). But the cheetah shot was only 400 ISO.

The cheetah cub shot was done through glass, into a very dimly lit "nursery" exhibit, which is why it's at f/2.8 and ISO 800. It has a bunch of level adjustment (B&W) (shooting through glass the original was very washed out), white balance, about a third of a stop exposure, and a tiny bit of extra contrast and saturation, plus the default Aperture RAW file settings for the 50D. A lot of the tufty fur is out of the f/2.8 DoF.

The adult cheetah in the same gallery was shot in an outdoor exhibit, in bright sunshine, with the 1.4x teleconverter on the lens. It has minimal post-processing, just the Aperture RAW settings, plus the same third of a stop and tiny bit of contrast/saturation.

Here's another shot of the baby cheetah, SOOC, nothing but the default Aperture RAW conversion settings:

--Ian

Overfocused · March 13, 2011

That's why its sorta blotchy... a tad underexposed compounded with all the other stuff

Strange bokeh?

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