Image Stabilization question

[keith_lubow]

I have heard that there are times when your IS can kick in unnecessarily and

cause an unsharp image. When is this? I shot a football game this weekend and

borrowed a 70-200 IS lens and Mk. IIN from a friend. Didn't even realize until I

was packing up that the IS had been on. I have never made any use of that

feature before since the only time I've had it was on rentals that I used

supported by a monopod. I think it may have led to some unsharp images. Almost

nothing is really tack sharp, regardless of how it was shot. Not totally out of

focus, and they will be usable when downsized and sharpened a bit, but the

results just look kind of like a cheap lens. Kind of like very slight camera

shake. I shot some action on a monopod in the second half, but I mostly took

hand held shots of the sidelines and stands, since there were several other

shooters not shooting these things, and a 200 is a frustrating lens to use for

football action anyhow. Shutter speeds were very fast; usually about '2000 to

'4000, and I was shooting wide open, usually at 200mm. I am used to using a

200mm fixed 2.8 lens (manual focus), so I know how accurate you have to be

focusing such tight shots, and that is not the problem in these cases. Is this

lens simply not as sharp as I am used to, or is the IS creating camera shake? I

have always heard that this is a very sharp lens, but I have shot a lot with the

non-IS f/4 version and what I got Saturday was piss poor compared to that. This

is not an issue of focus or depth of field. I suspect the IS, but I want to know

for sure. What do you think?

 

Keith

[peza]

I think you need to post a sample :)<br>

What I suppose is, you might have panned shots with IS in mode 1 and this can create some nasty effects.

[stillbound]

could be panning in IS 1 but it could just be that the 200 prime is far sharper...especially wide open than the zoom.

JC

www.pbase.com/josephwcarey

[keith_lubow]

<IMG SRC="http://d6d2h4gfvy8t8.cloudfront.net/6630958-lg.jpg"><BR>I can make them look OK. At least "good enough for most purposes".<BR><BR><IMG SRC="http://d6d2h4gfvy8t8.cloudfront.net/6630961-lg.jpg"><BR>But on close inspection, the areas that ARE focused onto the film plane are not sharp.<BR><BR>This one is actually pretty sharp compared to a lot of others. But you can see that the area of the image that is actually focused is not sharp. For instance, some strip of grass in every action shot has to be in focus. If you are anywhere close to focusing on the intended subject, SOMETHING in the frame will be sharp, regardless of whether or not you missed focus on the players. I can see the area of grass that is "focused", but it is still not "sharp".

<BR><BR>

The lens can't be that bad. It must be something I am doing, because I have used the f/4 and it is a stellar performer. The 2.8 must be even better, I would think. At least the same.

<BR><BR>

Keith

[keith_lubow]

BTW, pic #1 is downsized to 25%; my standard size for the 'net. Pic #2 is a 100% crop. Shot large jpegs.

[bob_osullivan]

For sports I would have IS off, unless it's race cars then IS mode 2.

This lens, like most Canon L lenses, is notorious for having significant copy quality varrience. Do a search here on "soft copy" and you'll see what I mean. This is probably just a case of your friend having a soft copy and not realizing it. This can easily be corrected by having the lens sent in for calibration or to correct a front/back focus issue. The lens should be tested first in a controlled way though. All the Canon 70-200s wether IS or not or F2.8 or F4 are superb when properly calibrated.

[peterlyons]

Dang, Keith... how sharp do you want it?!

 

For my purposes I'd call that perfectly good for any use. But maybe that's 'cause I don't

have any of the long primes to compare my images too.

 

It's true IS can cause you to get some slight motion blur if you don't give it a second or

two to get up and running before you shoot. In that brief moment, the floating elements

need to come up out of their resting position, and find their equilibrium. If you shoot

before they do, you may see some motion blur.

 

I don't see motion blur in the photo you posted.

[peza]

Well - it's gonna be the lens, not you. There is some subject movement involved and regardless of the shutter speed, I would not hope for pics sharp as a tack. <br><br>

 

I went back to my lens tests with 70-200/2.8L and I see <b>distinct</b> improvement in sharpness going from f/2.8 to f/4. <br><br>

 

Not to mention - by exposure I'm getting at f/2.8 on identical subject as in other f-stops is about f-1/3 too low. The same story with 300/4L IS.<br>

 

I noticed, with my 600/4L IS, stopping down, now hold yourselves, by 1/3 of an f-stop improves things noticeably. Since than, I never shoot it at f/4 but close down by f1/3. <br><br>

 

The only lenses I don't hesitate shoot at it's max. aperture are

<li>24-70/2.8L

<li>135/2L

<li>35/2<br>

But than - I didn't test the 24-70/2.8L as telephotos. 35/2.0 looks to my eye very good as well. 135 is supercool tool, PITA to focus dead accurate.

[peza]

BTW - under test conditions (heavy tripod etc) my tests went better with IS off. I can imagine in shutter speeds of 1/X000 second it's bettet to shoot w/o IS.

[lester_wareham]

IS takes at least 0.5 second from activation, by AF or meter activation say, until it has "locked on to" your arm vibration. If you fire the shutter within that training period it may reduce sharpness perhaps by quite a lot.

 

So if doing sports, portrait or wildlife work where you are waiting for the moment, you need to either keep the IS running and fresh for immediate use or turn it off so this issue does not arise.

 

Your example shot does not look too bad to me.

[keith_lubow]

I just pulled that example because it's the only one I have "printed" so far. Others are worse.

 

Thanks for the thoughts. I think it is a mixture of me being used to primes, and of not letting the IS settle, because I didn't even know it was on! In the shots where I took a little time to shoot, and was not trying to shoot something in motion (almost none, since that's generally not what you are aced with when shooting journalism), the lens was fairly sharp. Not great, but good for zoom. I know from experience that these shutter speeds will freeze football action extremely sharply. I usually use the f/4 with a TC, and get better results hand held. Also, no point in having a 2.8 lens if you aren't going to use it wide open. For sports using a long lens, I want the fastest possible shutter speed and the least possible depth of field.

 

Keith