K10D poor AF

Hi,

I could use some advice. I've had an MX and ME Super for a while, and built up a small collection of M and A primes. My DSLR has always been a Canon, with 50mm f/1.4 and 35mm f/1.4 lenses (shortly to be sold). A friend recently switched from Canon to Pentax, and I've been very impressed by the colours from the Pentax K10D, so I decided to follow suit and make the switch.

On Saturday, I took delivery of a K10D and 43mm limited from SRS. My thinking was that I'd pick a single AF lens (the 43mm), and then use my existing primes in MF mode.

I've found that the Pentax system is not really reliable with AF, even with apertures as small as f/2.8 (I do a lot of stuff at close distance). MF seems to be fine, although until I get a split screen focusing screen I won't know for sure. Is this typical?

I'm thinking about asking SRS to take the 43mm back, and just staying MF only. Is there any reason to assume that the newer lenses coming will be more accurate in their AF (as well as quicker)?

I've also been thinking hard about whether to keep the 43mm for MF only. It seems like a lovely lens, but it's also a shame to spend that money and not get reliable AF when I already have a 50mm M 1.4 which is wonderful.

In my position, what would you do?

I'd take the K10D back to the shop, along with the 43mm, and ask what is wrong. You shouldn't have AF issues with either, but it is not unknown for the body to need adjustment.

Obviously, the wider the aperture you use, the worse any mis-focussing will be.

G

I'd do what George recommends, take them back to be looked at....

With the 43 Ltd on a K10D there should be no problems whatsoever....

I would start by switching the AF to centre only (there's a custom menu option on the K100D) and checking whether the focus is better. Maybe the camera was taking focus on something that had higher contrast.

Additionally, do not use the Red overlay indicators as a guide to accurate focus! The red only shows which focus point is being used. You must use the Green hexagon at the bottom of the viewfinder for manual focus - that is the only reliable indicator.

Failing that - as has been mentioned, get it looked at
Matt

Thanks all for your input. I'm using centre focus point only. I have focus turned off on the shutter button, and use the AF button to focus. I think perhaps I've been tripping the shutter when the red light shows up, and not waiting for the focus confirmation beep.

I took a few shots tonight and it did seem that if I'm just patient and wait for the focus confirmation beep, it's focusing "ok". Still not sure it's brilliant, but it's much better. I need to change my habits! Focus is still slow in low light though

I'm surprised...

I've just had a go at using a Canon 30D with 24-70 f2.8 L series lens and it was unbelievably slow at focussing even in moderate light. I find the K10D much, much faster, and the *ist-D was perhaps slightly quicker (EDIT: slightly quicker than the 30D. The K10D is very fast indeed!)

From what I understand, though, the 31, 43 and 77 Limiteds were designed with some serious focus damping to allow for silky smooth manual focus. A consequence of that is that the AF is (AFAIK) slower than the other Pentax AF lenses.

All the lenses I have are SMC-F, SMC-FA and SMC-DA and they are very very quick at focus - but I find a right pain at MF because they are completely undamped.

Maybe that's the "problem" you're experiencing... maybe someone who has the Limiteds can confirm the difference in AF speed...

Matt

Interesting! Thanks for the feedback, that's really useful. Perhaps I should try to persuade my friend to let me borrow one of his DA lenses.

I would agree with Matt that the focus on the Limiteds is slightly slow compared to some other lenses, but it's not SLOW, just not quite as quick.

I think there is a problem somewhere.

G

I need to be really careful about this. You know how it is... it's new gear.... you're frustrated.... you jump to the conclusion that it's not working right.

I'm going to take my time and test this carefully tonight. I've been out with it in broad daylight this lunchbreak, and don't have any complaints about the speed of focus in those circumstances. Most of my targets at lunch were distant (>3 metres) of course, whereas the ones I've struggled with have been quite close (e.g. 1 metre) and lit only by low energy indoor lightbulbs.

I presume SRS aren't going to have a problem with me reporting an issue with the camera/lens on Tuesday after having received it on Saturday, so I'll give it tonight, and report back.

OK so it's obvious, tripping the shutter before focus has been achieved will result in out of focus images So thanks for bearing with me whilst I embarrassed myself with that.

It's still significantly slower and less accurate than the 20D, but I think I can live with it. The SR lets me close down the lens a bit, so I can get in the ballpark of what I could achieve with the 20D, sharpness wise.

AF will be much better with the SDM lenses due soon (same as Canon USM).