The f-stop sweet spot...

The f-stop sweet spot..., originally uploaded by Venn Diagram.

A tip I picked up from this month's PhotoPlus magazine. Thought it worth passing on as I think it works quite well.

Most lenses suffer at each extreme of apeture, and each also has a sweet spot at which the clarity of the image will be greatest. You can buy charts and stuff (for a price) to help you figure out where the ideal f-stop lies. However, if you get something with enough detail on it (these are the share pages from today's Guardian, the text is pretty small), you can take a series of shots and make your own judgement.

From left to right we have:

f22 - lens stopped right down - the image here is pretty good, If you looked at it alone, you'd probably think it was alright, the difference is RELATIVE...

f8.0 - the sweet spot, as established from a whole set of photos and a lot of pretenting I'm in the optician's (is it clearer and brighter now, .... or now). You can see all the extra bits of ink, the roughness of the paper and the text is sharp enough to cut yourself.

f2.6 - wide as it gets - you'd expect a bit of blur at such a wide apeture, I guess, but not only is it blurred, it's green! It's still "not bad", and I guess I've been shooting a lot of photos like this and thinking "they're just not as sharp as x's shots" or something similar.

So, one lens down, three to go, but I've made a promise to myself to try shooting at f8.0 with this lens for a while and see how it works out....

EDIT : These shots were taken with a Sigma 70mm Macro lens - the most expensive lens I've purchased - if this is the case for a super piece of glass, I'm keen to see the effect in my 18-55mm kit lens...