The ultimate focus test?

[David Kilpatrick]

I tried focusing on a distant swarm of midges in the last rays of the sun in the churchyard with the 70-200mm HSM on the A900. Guess what? It locked on no problem.



May not look like much but here's a 100% clip:



That is at ISO 320 - I have no worries about using ISO 320 routinely. Midge in the middle clearly focused, sharp, body resolved at f/4 and 200mm - only 1/160th shutter speed, really these bugs need 1/1000th or shorter to freeze their movement.

David

[01af]

That is at ISO 320 - I have no worries about using ISO 320 routinely.

What is this "ISO 320" thing about? I keep reading about it a lot lately but I'm afraid I don't fully understand.

I do understand that in the Alpha 900 at ISO 320/26°, noise is significantly lower than at ISO 400/27°. So I have now developed the habit of using ISO 640/29°, ISO 320/26°, and ISO 160/23° rather than ISO 800/30°, ISO 400/27°, or ISO 200/24°. I do not understand, however, why people are so keen on using ISO 320/26° specifically. While noise is lower than at ISO 400/27°, it still is higher than at ISO 160/23° or ISO 100/21°.

So when shooting hand-held telephoto lenses, ISO 320/26° sure is a sensible setting to use. But when I don't need that speed I always try to select lower speeds, as conditions permit. Am I missing something?

-- Olaf

[David Kilpatrick]

I use ISO 320 or 160 mainly. ISO 320 is the highest setting in which very little noise appears in blue skies, so it's ideal for good quality scenes where an action-stopping shutter speed is needed. I use it because it is the highest ISO which produces the quality I want.

David

[caporip]

I tried focusing on a distant swarm of midges in the last rays of the sun in the churchyard with the 70-200mm HSM on the A900. Guess what? It locked on no problem.
David

I sense a photo challenge!

On a slightly related subject i have just been rereading (due to an imminent house move) some of my old photography books. One in particular always knocks me out and that is Stephen Dalton's caught in motion. He used a "light tunnel" to to photograph flying insects. Theres a shot in there that was a complete accident - when the the infra red trigger was set off by flying aphid. The book shows a crop of, i think, Kodachrome 25 shot and the detail is astonishing. So maybe that should be your next assignment, David

[artington]

The ultimate focus test?

Nope...try focusing on just a single midge. Your subjects are sorta working like a window screen, and we all know cameras do like to focus on window screens. I'm just sayin'.

-Sonota

Absolutely, although personally I usually do this (ie single midge) manually

[Greg Beetham]

Well I think it's pretty amazing that the focus stopped in the midges instead of focussing on the more solid background...yeah with 1/1000sec and maybe f5.6 (there is depth to the midge cloud, I can see some oof ones) that shot would have been really cool.
Greg