Canon EF 75-300

[rickm]

Canon 40D @ 260mm, 1/1250, f10, ISO 400

[digitaldude400d]

Rick, great shot. I have this lens and am using it on a XTi. Is the reason my images arent this sharp because of the difference in cameras? Seems no matter if its tripod mounted or not I dont get sharp images.

Thanks,
Jere

[rickm]

I doubt the sharpness difference is due to the camera differences. The first thing I would test is to make sure the camera/lens combo is focusing precisely where you intend. Here is a page with a downloadable PDF to print that give good instructions and test charts to use. You could also set up a test with a series of object at various depths and see if any are very sharp. You could use medicine bottle or food packaging - anything with small print on it that can be put at different distances from the lens but close together to check focus precision.

Also, while the above shot looks sharp it is a full image with no cropping that has been reduced in resolution which helps make it look sharper. I do not find this lens to be particularly sharp especially for enlargements or looking at individual pixels. I was borrowing this lens from a friend and decided to buy a different lens because of its softness, especially at 300 mm, and slow focusing speed. Here are two images from the exact same spot of the UT football stadium taken with a Canon 40D. Both of these are 100% crops. The first is the Canon 75-300 at 300mm f/6.3. The second one is the Canon 70-200L + a Tamron 1.4x SP Pro teleconverter at 280mm f/8. It is clear how much softer the 75-300 is even when considering degradation added to the 70-200 f/4 by the 1.4x teleconverter.

[rickm]

One more thing that is basic but I thought I would mention is that I would ensure when you are taking photos is that you keep your shutter speed at least 1/focal length or greater. Thus if you are at 300mm, keep it at 1/300 or faster if possible.

Also note that I would expect this lens to be sharper stopped down between f/8 - f/11 than wide open.

[digitaldude400d]

Rick, thanks so much for the information. I thought that the lower the f stop the better the image would be. Ill have to test shooting between f8-f11. So it would seem that this lens needs a LOT of light to produce decent pictures then? This would explain why I have only gotten a few good pics with it....or at least explain a good part of why.

Jere

[kenw]

The lens is perfectly capable of very sharp work, here's one scanned from film, on tripod racked out to 300mm.

http://www.texasphotoforum.com/galle...28&ppuser=4447

Yes, at f8-11 you'll need a fair amount of light, but it's not thermonuclear-dependent. As that F stop drops (bigger #), the shutter starts to impact the results and depending on how much you want to freeze the action, that may give you some problems.

[digitaldude400d]

WOW Ken thats an incredible picture! Ill be at the Fort Worth zoo next Friday and can only hope to get something a quarter as good as that.

How much of a difference is it because of being on film?

Thanks,
Jere

[kenw]

Thanx, I actually think the difference is minor, since this was scanned from a negative at only a moderate resolution. I think my ancient 10d could do as well or better with the same lens.

I do know I would have known if I had a keeper without burning an entire roll of film, and waiting to return to the US to see if I had any keepers at all!

[Texas_Flower]

Here are some photos taken with my new T2i and the 75-300 lens it came with.