[Larne]

Hello again.

Thanks for the prompt and informative responses.

The D70 focus chart is an excellent idea. Using that the line where I get sharpest focus on my 50mm is the one marked 10mm in front of the focus point. I tried it on f/1.8 and f/2.8 and I get the same result in both cases. So it looks to me rather like the lens is past it - it is old (it was second hand when I bought it a decade ago) and today I actually had it lock up at f/2.0 and cause the camera to shut down with an Er99 so I am guessing I need look no further.

Results on the EF-S 17-55mm are much more encouraging. At 17mm f/3.5 the target is perfectly sharp with the depth of field extending approx 1/3 in front of the point and 2/3 behind (as I understand it should be). At 55mm f/5.6 it is perfectly in focus, to the extent that I can actually see the texture on the paper. Sure it is soft but a quick run through the Unsharp Mask filter on Photoshop elements turns it nice and crisp.

Thanks again for the help. At least now I know the problem is the 50mm lens and I will be disposing it once I work out the best way of recycling it. I will run the same tests on the EF 28-135 when it arrives and hopefully they will be positive.

Cheers,

Niall