Lens tests ...

jackdaw

Hey
I remember reading a post here about some problem with a 70-200 IS f4 (or maybe 2.8?) L lens .. its focusing was off on narrow apertures on some photos,

It could focus ok with shallow DOF but with deeper DOF it was a bit dodgy on some areas ...

What should i do to test my lenses fully, ? just take a few test images on f2.8 on 70mm
and 200mm (focusing on certain object) .. and then test at f22 (or more) at 70 and 200 .. with deeper DOF ..


Is this problem common with L lenses ?

The reason i say this is because i was at dublin zoo at the weekend with my 70-200L f2.8 IS and i wasn't delighted with my pics .. i was expecting this to
be a C&C post .. but some of the animals looked a little off focus .. now im
sure it's not the lens as i have gotten other very sharp shots before ..
I think it's just the animals were moving a little..
and i shot at too slow a shutter speed .. but id like to do some tests to be sure ..


my other L lens is a 24-70 f2.8 ..

Tactical

I feel this is more a body than a lens issue.

I've heard of two people who have reported similar issues.

One chap shoots horse racing events and isn't wet behind the ears by any means. His comments (& shots) have flying mud and other stuff sharply in focus but not the horses.

Another guy who was shooting product was getting fine sharp shots close up and with varying DOF from shallow to deep but when trying to obtain a group shot from about 2.5 mtrs a sharp shot just couldn't be obtained with any lens or DOF, manually of on a semi mode.

Interestingly both were Canon bodies (different ones) and both were using Canon lens. The product guy also had a Tamron lens with him and stated the same results. He initially put the lack of sharpness to the lighting for some reason, I don't know why though.

ttcomet

Do you mean this thread?.

This page has downloadable focus charts and instructions on how to use them.

Maybe you can post one or two pics with the exif data and we may be able to help work out the issue.

Tactical

No, not that thread. It wasn't in any way related to boards.ie

Fajitas!

It sounds like it could be shake more than a problem with the lens really. Starting off with a 70-200 means you're going to have to deal with shake a lot more, especially coming from the 24-70, where shake won't do as much damage. Trying using TV mode more and more, I find it useful in situations like that.

jackdaw

Thanks guys ..

ok look at this ..

he's not so sharp .. (Exposure: 0.008 sec (1/125)
Aperture: f/2.8
Focal Length: 200 mm
ISO Speed: 100)

http://farm4.static.flickr.com/3141/2851786210_57029ed3cc_b.jpg


neither is he : (Exposure: 0.004 sec (1/250)
Aperture: f/2.8
Focal Length: 200 mm
ISO Speed: 100)

http://farm4.static.flickr.com/3069/2850912529_6a62c68b7a_b.jpg




This one
http://farm4.static.flickr.com/3220/2851467346_09e8fdc4aa_o.jpg

is at Exposure: 0.003 sec (1/400)
Aperture: f/2.8
Focal Length: 200 mm
ISO Speed: 100


but looks ok to me ..

Tactical

Oh yeah,

It might be worth mentioning that in the product example a sturdy tripod was used, along with timer release and mirror lock up.

DaireQuinlan

I'd say it's down to your ability to hold the camera steady more than anything else. I don't think I'd try and get away with 1/125 at 200mm unless I absolutely had to, and I'd probably expect a soft image. Its no surprise that the one shot you took at 1/400 is ok. I'd practice your handholding technique a bit, or use a tripod.

jackdaw

DaireQuinlan wrote: »

I'd say it's down to your ability to hold the camera steady more than anything else. I don't think I'd try and get away with 1/125 at 200mm unless I absolutely had to, and I'd probably expect a soft image. Its no surprise that the one shot you took at 1/400 is ok. I'd practice your handholding technique a bit, or use a tripod.

of course ... stupid .. i forgot the golden rule .. shutter speed should be at least that of the focal length when handholding ..


edit -- what an anti-climatic 1,000th post !!

nilhg

jackdaw wrote: »

of course ... stupid .. i forgot the golden rule .. shutter speed should be at least that of the focal length when handholding ..


edit -- what an anti-climatic 1,000th post !!

And don't forget the crop factor, 200mm on a Canon crop body is 320mm effective.

ttcomet

jackdaw wrote: »

of course ... stupid .. i forgot the golden rule .. shutter speed should be at least that of the focal length when handholding ..

At least it is good news that your lens is fine.

jackdaw

yes .. it would be such a pain in the ass to ship it back off to HK ..