Sharpness issues with Canon 100-300mm

Hello,

I have a Canon 100-300mm lens. When I take pictures with the lens fully extended the photographs often

look ok at full frame but the focus and/or sharpness looks bad at 100% crop. I often use the lens fully

open at F5.6 so maybe this is to be expected at this F-stop and with this relatively cheap lens? However

even at F-8 the pictures are not great.

The problem is I'm not sure how to judge wether I have a bad lens or a lens that perhaps needs calibrating

to my 20D body or if the results that I get are to be expected for this quality lens/ F-stop etc?

Does anyone have (or can direct me to) any photographs that demonstrate the quality of image one

should expect to get at 100% crop for both higher and lower quality lenses, just so I can better judge if

my lens is working correctly or not?

Attached is an image taken at 300mm, F5.6,1/1600sec,100ASA, handheld, 100% Crop

Thanks for any advice you can give

Kirsty<div></div>

Looks OK to me. Which 100-300 is it? There have been 3 different versions. The 100-300/5.6L is the best. The 100-300 USM is the most common and an OK lens but gets soft at 300mm.

At 300mm, inexpensive zooms simply aren't critically sharp. Very few lenses will give images that look critically sharp at 100% crop. With a typical monitor it's like looking at a 24" x 36" print.

The practical way to judge useful sharpness is to make a print of the size you want to make and see how it looks.

I have some comments on sharpness testing here - http://www.bobatkins.com/photography/technical/lens_sharpness.html

"<I>Does anyone have (or can direct me to) any photographs that demonstrate the quality of image one should expect to get at 100% crop for both higher and lower quality lenses"</I>

<P>

I don't have a 100% crop from a lower-quality lens handy, but here is a photo from a high-quality lens. First is the full picture, second is a 100% crop:

<P>

<CENTER>

<IMG SRC="http://wildlightphoto.com/birds/falconidae/L1002368.jpg">

<P>

<IMG SRC="http://wildlightphoto.com/birds/falconidae/L1002368crop.jpg">

</CENTER>

Here's a 100% crop from a Sony 70-300 I've been testing. Shot wide open at 300mm (f5.6) with a Sony A700 12MP DSLR. The Sony 70-300 is probably similar in quality to the Canon 100-300. It's a fairly low cost consumer lens.

The image is somewhat soft, but it's what you'd expect from such a lens. The crop is from the center of the image. Standard camera settings, no shapening applied.<div></div>

Bob - that crop looks similar quality to the crops from the Tamron 200-500. How would you compare the 2 lenses? My brother-in-law has a Sony system and is considering that lens.

TIA

I've been shooting wildlife with this lens for the past 2 years. I'm not sure why but sharpness seems to be hit and miss. Sometimes I get shots that I don't have to sharpen at all and sometimes I get images so blurred they are unusable.

The image you've provided I would stack under a miss.

A most telling moment was when I using it to shoot portraits and about 1 in 5 photos were perfect and others slightly blurred. It wasn't me (tripod similar exposure times) and it's not my 30D (other lenses do not have this issue on my camera).

You could have an AF issue. Maybe the lens you were using has more AF "slop" than your others do. There's always some degree of uncertainly in AF and the spec is simply "within the DOF" for most consumer lenses and bodies.

Apparent sharpness can also depend a lot on the subject being shot. High contrast subjects look sharper for example and there's a subjective effect that subjects which fill the frame look sharper than if they are a small part of the frame, even though both images may technically have the same resolution.

I wouldn't attempt to compare the Sony lens to the Tamron because I've not shot the same subject with both of them on the same camera. Neither one is very expensive and so neither one is going to give you razor sharp images at full zoom. I do have some comments on the Tamron 200-500 here - http://www.bobatkins.com/photography/reviews/tamron_200_500.html - where I compare it with a few Canon lenses.

<p>Hello,<br>

So sorry for my late response (I checked this site a few times after I left the message but did not see any comments to my post and as I have not checked the site since, I missed these messages until now !). I know its a long time since but thanks anyway to all of you for your comments and photo examples. This has been extremely helpful!</p>

<p>Kirsty</p>