Image Anomaly; Opinions

[john-pa]

I sometimes (but not always) see what I think is an anomaly in my images. I can’t decide if it is; a) Just Normal; b) Me; c) The Lens; d) Something else. I would like some opinions on this.

The link is a larger 1200x800 example on Flickr. The basic data for this example is;
Canon 1DmkIII; EF 24-105 f4L IS; 105mm; f5.6; ISO-400; 1/1250-sec; -1/3ev; IS-on

What I am concerned about here are the ghost-edges on the flower petals. You can see this most clearly at 9-to 10-o’clock. This doesn’t look like normal DoF blurring to me, because the edges of the ghost image are so sharp, and it is that sharp ghosting that makes this distracting.

One thing that I was wondering; I usually leave IS on all the time. In this case, because I was chasing bees around I was snapping the shutter rather quickly too, almost concurrent with the AF/AE acquisition beep. Is it possible that I could have caught the IS shifting the elements? On the other hand, the shutter is so fast that I would not have expected that to be an issue. Thoughts?

Thanks

J

[Old Ben]

A few questions:


(1) Could you be getting a reflection off of a filter mounted on the front that is causing the double image?


(2) Is the double-image always in the same place in the frame, which may suggest a problem with the glass in the lens?


(3) An observation....it looks like the flower petals each come to two points. Is it possible that what appears to be a double image is an out of focus image of those two points? I am assuming the answer is "no" because it seems like this phenomenon is not specific to this one picture. Had to ask though...


Only my thoughts....I'm certainly no expert. Good luck though.

[john-pa]

Well, an artifact from a filter is another theory. I do use UV/Haze filters on all my lenses for protection. Based largely on Bryan’s article on the subject here though, I use good quality B+W MRC filters and I also always use a hood. Perhaps, however, that is not enough especially when (as here) I am working at close to the shortest focus distance of the lens. I don’t notice this often enough to say what else may be common factors.

Thanks

[wickerprints]

What is truly puzzling about this image is that you see the doubling in the petals but *nowhere else*. That is absolutely bizarre. If your stated shutter speed is correct, there is NO way this could be caused by IS. 1/1250 is certainly fast enough to stop camera shake as well as most any kind of subject motion, and I doubt the petals on an inanimate flower could be vibrating that fast.


The center sharpness is another clue that this is not due to motion. If anything were moving--camera, lens/IS, subject--then you probably wouldn't have a pin sharp center. So I am tempted to conclude that this is an issue with the optics somehow. By eliminating what the problem could *not* be caused by, what remains, however improbable, must be the cause. (To paraphrase Sherlock Holmes.)


As to what particular optical issue could cause this phenomenon, it is quite possible it is due to a filter or some kind of internal reflection in the lens. You will have to conduct more extensive testing to confirm or refute this possibility. Best of luck.

[piiooo]

I think this is a type of out-of-focus blur, because the double edge on affected petals gets more prominent as it ismore distalfrom the focus area. This is much more obvious on full frame bodies because they provide more shallow DOF. I had a similar experience when I put a 100 2.8 macro on a 5D Mk2 for the first time, butnever thoughtmuch about it.


IS would haveblurred the whole thing. A UV filter would have caused flare more likely.


If you want to find out for yourself, try to reproduce the effect and then see if it goes away when you use smaler apertures.


Take care.