06 December 2009

Southern Fulmar

Pentax K-7, DA*60-250/4
1/1500s, f/5.6, ISO 400
Click image for larger version

The DA*60-250/4 zoom was by good margin the most used lens on my trip. Combined with the K-7 it's adequate for many wildlife action situations. Consider this one, for example. The autofocus was set to multi-segment, and as all AF systems it tend to prioritise the brightest elements in the frame. Yet it had the wits to stick to the bird.

That said, I think Pentax still has a way to go with their AF system. I notice the K-7 is a big leap forward compared to any previous AF camera from Pentax when it comes to track-focusing, but there's still a good gap up to Canon and Nikon in this respect. And Sony too. To get a sharp shot in a situation like the above, one has to expect a considerable number of mis-focused shots. There's a lot of variables, though. White birds against dark background gives a good hit rate. Lower the contrast, and Pentax bails out sooner than the others. Try to photograph brown birds against blue sea and you're lost with Pentax. I threw away 90% of my pictures of giant petrels in flight obtained under similar conditions.
But then again... The main key to successful photography is to know the strengths and weaknesses of your gear. The K-7 has a lot of strengths to show for itself. And I think I'm getting better at catching these critters as they fly by, too.

3 comments:

Sune said...

Beautiful shot !

Some rumors indicate a new AF system with the next high-end DSLR from Pentax.

Else when one Pentaxian shooting motor bikes, finally went with Nikon D300; to start off with he didn’t see any improvement in keepers, though he had thought he would. But I suspect when he got better acquainted with the cam, his ratio went up.

One Pentaxian birder I followed quite a bit, was Dominic Cantin :
http://forums.dpreview.com/forums/readflat.asp?forum=1036&message=22312032&changemode=1

Alunfoto said...

One of the guides on board was a pro photographer; Ole Jørgen Liodden. In his talks, he recommended the Canon crowd to use centre-point AF sensor only, for track-focus. His argument was that "it's the best sensor site, and single-point AF makes the camera work faster". My room-mate had a new Canon 7D, and he demonstrated how Canon has coupled the centre sensor with a few surrounding points to make a high-performance crosshair-style AF mode for track-focus.

For Pentax, I think that's the weakest link in the AF system. When using multi-point AF, the sensor roundtrip before acting on misfocus is too slow.

I have some more thoughts about AF development too. It's already partly written in an unpublished post; I'll try to finalise it soon.

Thanks for commenting, Sune. It's much appreciated.

Sune said...

I completely agree. Tracking is the worst part of the Pentax AF system. Generally it is often recommended using the center AF point. On some Nikon and Canon cams, they are loaded with AF areas, so a subject moving from one to the next can be detected.

Sounds cool that the Eos 7D has working crosshair-style AF mode.
Will be looking forward to your article on AF development.
It is much appreciated to see these shots, and thanks for not taking my comments as critique to your writing.

I’m fighting with some exams at my study that I’ve tried before. Looking at these pictures have been a nice dream away. Thinking that maybe someday, I can get to see some of these or other magical places.