Is it normal to get halos around highlights with the 70-200 IS?

[steve_dunn2]

<p>I just bought a new 70-200/2.8L IS USM for my 20D, to

replace a 300/4L IS USM which is longer than I want now that

I have the 1.6x cropping factor to take into account. In doing some

quick testing, I've noticed that some shots taken towards the long end

of the range, with or without the 1.4x II teleconverter, have

unpleasant halos around highlights.</p>

 

<p>For extreme highlights, like sunlight reflecting off a pool of

water, I can understand that, but I'm also getting it in situations

where the contrast isn't extreme, situations in which none of my other

lenses (300/4, 50/1.4, 17-40/4, 28-135/3.5-5.6) do not show this

effect. Here's an example. 20D, 70-200@200, ISO 100, focus on the

left eye (and at 100% the eye is tack sharp), 1/100s @ f/3.2 in Av

mode, handheld, IS on, diffuse natural light. First, the full frame,

downsized and saved at low quality:</p>

[steve_dunn2]

<p>Hmm, don't know why that isn't shown inline; it's smaller than the 511 pixel width. Anyway, now here's a 100% crop from near the bottom left. The whiskers are out of focus, but the halo looks unnatural to me.</p>

[steve_dunn2]

<p>Am I worrying about nothing? Or is this a fact of life for a zoom with so many elements (although the 28-135 isn't far behind in this regard and doesn't seem to have this issue)? Or should the lens go back to the store?</p>

[phule]

<< Hmm, don't know why that isn't shown inline >>

 

You likely need to include a caption.

[ben_kriete]

Your shutter speed is slow enough I wonder if maybe the whiskers moved a tiny bit, enough to show some ghosting. Maybe in general you are shooting slower shutter speeds than you would without IS? Just a thought...

[steve_dunn2]

<p>Rob, thanks. I'll keep that in mind.</p>

 

<p>Ben, I thought of that, but that's not it, at least not in general. I get the same effect in handheld shots of stationary subjects (e.g. a neighbouring building) at 1/500 or faster, and it seems to happen only around highlights; everything else is sharp and free of ghosts/halos. I first noticed this effect in a picture of my cat which I took at night, using flash bounced off the ceiling as essentially the only source of light. He's quick, but I don't think he's <em>that</em> quick :-)</p>

 

<p>I'll try to see if I can duplicate this in a fashion which rules out subject or camera motion.</p>

[ralph_jensen]

"Is this a fact of life for a zoom with so many elements?"

 

I'm guessing that's it: if I recall correctly, the 70-200 has far

more elements than any other Canon lens of any kind (22? 23?) and

there have to be some side-effects of all those layers. Mine's a

great performer but I've never studied the highlights that way.

[jon jacobson]

Tough to say based on just this portion of just this image, but perhaps Toby is not the best subject for bench-marking? Kind of looks like bokeh. Maybe.

<p>

Perhaps<br>

a.) Toby flinched at the preflash, and/or<br>

b.) the DOF is so narrow (200mm x 1.6 at f3.2) the wiskers could be naturally out of focus.

<p>

I'm sure you've thought of this, but hey, it's worth saying out loud; tripod, cable release, turn off IS, and set something up that won't move. A fresh (white, not yellowed) newspaper laid out at an angle is a popular choice.

[rog21]

No, I don't think that is normal. I have never seen that with my 70-200 2.8L IS. I have allways used it on a film body though and wondered about that effect when I saw something like it in a thread about using the 2X with it.<br><br>

 

Well, this last weekend I was visiting my cousin and she happens to have a Rebel XT. Of course I couldn't resist trying my good glass on her DSLR.... and it just happens that I shot a photo of her cat.<br><br>

 

Full shot:

<a href=http://www.photo.net/photo/3988264>Cat</a>

<br><br>

Crop of whiskers:

<a href=http://www.photo.net/photo/3988287>Crop</a>

<br><br>

I do not see the effect in my shots. Since the XT is 8mp and a 1.6 crop like your 20D, I would think all else would be the same.

[ted_marcus1]

At first glance it looks like the whiskers were just slightly out of the depth of field (which should be rather narrow with such a long lens). But at second glance the halo looks distinctly greenish. Could chromatic aberration be involved, possibly combined with out-of-depth?

[mark u]

This could be influenced by the quality of foreground bokeh:

 

http://www.vanwalree.com/optics/bokeh.html

 

Look at the later parts of the article.

[les]

I don't know, maybe I am seeing ghosts, but it appears (to me) that the width of the "halo" increases toward the end of each whisker - which would indicate movement (of the cat's head). Can you check if there is evidence of movement in other parts of the picture ?

[steve_dunn2]

<p>The parts of Toby's head which are in focus are very sharp, so it's not that his head moved. But it's certainly possible that he moved his whiskers while keeping his head still; these little critters' whiskers have a pretty big range of motion. Yes, there is some chromatic aberration there.</p>

 

<p>I originally saw this in shots of Toby taken the previous night, in a dimly lit room, using flash. My gut feel is that the ambient light wasn't anywhere near bright enough to produce motion blur; the halos on those pictures were almost as prominent as on the picture I posted. And I'm pretty sure flash is fast enough to freeze whisker motion. But I can't categorically rule it out; I didn't meter ambient light separately before taking the shot so I don't know for a fact how many stops down it was.</p>

 

<p>I've tried to reproduce this since (both with Toby and with inanimate objects), but Murphy's Law being what it is, I haven't been successful. I've tried to reproduce it using similar technique to what I used on the shots with these odd effects, and I've tried to reproduce it using technique which should rule out subject motion, camera motion, and bokeh; no dice. I find it a bit odd that I've taken <a href="http://www.stevedunn.ca/photos/toby/" target="_blank">pictures of him</a> with pretty much every lens I've owned in the 7+ years I've had him (300/4, with and without 1.4x; 50/1.4; 17-40/4; 28-135; 28-105), always handheld, using IS on the lenses which have it, with various mixtures of ambient and flash, and haven't seen this before.</p>

 

<p>WRT the number of elements, this lens has more than any other lens I own, but only slightly more than the 300/4 IS with the 1.4x TC. And the 28-135, while several elements behind the 70-200, is not exactly lacking in air-to-glass surfaces, either.</p>

 

<p>Otherwise, I'm thrilled with the lens; it's sharp wide open across its entire range, seems sharp even with the 1.4x on it (I'll be doing some testing to see how much benefit there is to stopping down a bit with this combination; there's a definite difference between wide open and one stop down on my 300/4 IS with the 1.4x), and of course blurs backgrounds very well. If I can't make the halos come back, I'll have to conclude it was poor technique on my part and accept that the lens is truly excellent :-)</p>

 

<p>Thanks to all for your suggestions.</p>