View Full Version : E-420 Contrast AF on older lenses works... + 25mm full res shots

7th March 2008, 04:10 PM
To quote another forum

"For those of you that don't read Spanish:

In the press release Olympus states that only Zuiko 14-42 mm f3.5-5.6, 40-150 mm f4-5.6 and the new 25 mm f2.8 can make use of the new contrast autofocus. Quesabesde made a test with the older 14-42 lens and the 14-54 lens. The contrast autofocus did work also with those lenses, although it is only possible to use three focus points and Facial Detection does not work. But focussing is performed correctly, without mirror slapping back and forth."

This is in reference to this link (http://www.quesabesde.com/noticias/olympus-e-420-analisis-muestras-zuiko-25mm-f2.8,1_4146). It also includes what seem to be full res jpegs taken with the 25mm f2.8 (very impressive looking btw)

So this brings me to my question. Does anyone know a technical reason why contrast detect AF shouldn't work with any lens? Is it simply a case that the camera relies on a 'contrast profile' for each lens to fully function? I could imagine that they use this to make it faster, and with other lenses it is slower so they don't want to officially support for fear of disappointing. This perhaps makes it likely that Firmware updates to lenses will add these profiles and so expand the use. Or am I way off base? Any ideas?

All the best,

ps - have a look at the 25mm samples. It looks like CA is VERY well controlled. I don't own any of the kit lenses (except the 14-54) but this looks a cut above. Perhaps Tatsuno does have some meaning...

7th March 2008, 04:17 PM
The samples are impressive. It looks like this lens could be a goody especially with the smaller 400 series bodies.

Ian C.

7th March 2008, 04:49 PM
I'm just finishing off a technical article for Four Thirds User on this subject.

The 25mm, 14-42 and the 40-150 f/4-5.6 are all contrast AF mode compatible but the latter two already out in the wild require a firmware update.

The interesting news is that Olympus Japan confirmed to me that the contrast detect AF system should be compatible with Panasonic's system as demonstrated in the DMC-L10 DSLR. So contrast AF in live view should be possible with the Leica 14-50 f/3.5-5.6 and the 14-150.