Focusing

With regard to the sluggish focus evident on many smc lenses that i have witnessed over the years, does anyone out there have any suggestions on improving focus speed and technique. I have recently purchased a DA 16-50mm which seems to be moderately faster compared to my kit lens and my fixed 35mm FA, but I am still having problems to capture that split second moment in all its glory. Do you think the centre focus is faster than multi point? Any feedback at all would be greatly appreciated, as this issue for me is a constant problem when dealing with pentax, compared to the speed over other marks like nikon etc.

I always use centre focus and normally prime lenses, so no major focusing issues. Depending on the situation, I also pre-focus on something near my expected moving target, like the old film days, hold focus and fire when the subject is at or near the prefocused position. Again, depending on the situation, depth of field wil take care of any errors.

Incidentally, this bit of software looks amazing;

http://www.focusmagic.com/

I use centre focus which I lock with a half press on the shutter release before reframing (if necessary) and firing the shutter. It takes less time than focusing manually ever did and just snaps into focus 95% of the time.

I wonder what sort of subjects you are shooting and in what sort of light? Perhaps it would help us make some suggestions if we knew that?

I think quick-shift focus deserves a mention here.

Most DA lenses have a clutched focus ring so you can manually change the focus point even when the camera is set to AF. I have found this really useful when shooting fast moving distant objects, like aircraft and birds.

It allows you to get the lens roughly in the right place and then let the AF finish it off. Doing this usually avoids the problem where the camera chooses to to perform an end-to-end focus hunt while the subject vanishes over the horizon

Glyn

To clarify, in most recent times, for example, while traveling on a motor bike through the vietnam countryside i found myself having to whip out the camera quickly while moving quite fast on the bike (a difficult situation, i know). Having my FA 35mm lens on board, i tried taking hundreds of candid shots of village people and children in a descrete manner. When looking at the pictures at home, all excited to see how they turned out, i found 80 percent of them where out of focus, mainly back focusing was the major issue evident. Since then i haven't been able to test out my new Da 16-50mm with regards to focus speed under extreme situations, but i feel that the major issue may have been that i was using multi point not centre point focusing.

What are your thoughts? and thanks everyone so much for the feedback. I can't tell you enough how this helps me in improving my technique.

To be fair, that is asking rather a lot of any AF system! I hope you were riding pilion

Under those circumstances, putting aside that I'd probably be more concerned with holding on than taking pictures, I think I'd shoot high ISO and small aperture in continuous shooting mode, and hope for the best! I'd probably use manual focus but that's probably just me. Your pictures from Vietnam are excellent if I may say so, I really enjoyed looking at them on your website.

The technique for candids as you describe is to get in close, set the lens manually to the hyperfocal distance and leave it there. Don't even try to focus under the conditions you describe.

I would suggest starting with a fairly wide angle lens (the 21mm or even better the 15mm) set the aperture to f8 or f11 and just make sure the shutter speed will be reasonable. Then just focus on about 10 feet away and leave it there.

This sort of thing on film used be done with a 28mm or even a 24mm lens.

You do need to get in close for these sort of candids though, so a bit of confidence helps that. Looking nervous makes the photographer look as though he or she is up to no good, and that's not a good idea these days.

That's how we used to do it in my press photography days when covering riots. 28mm lens set to f8 and focus distance set to just over 2 metres. Bright line Leitz finder fitted over the rewind lever on the Nikon F Then just wade in.

No focussing beats AF for speed by a wide margin!

Lemmy that's very interesting I wouldn't have thought of using a viewfinder on an SLR. Just as an aside was it an issue having only 36 shots per roll?

Mike

You can change a film in not much more than 10 seconds, so it isn't a problem, even in fast-moving situations. You also picked the timing for each shot more carefully, so 36 shots actually went quite a long way. My God, how time flies.

Al

I'm not sure I could have changed a film in a riot too well. Certainly not on the M3 which was decently fiddly. We have moved on haven't we? When I started with digital I was still being reserved about taking shots as I was with film - a friend roundly told me off. Now I'm far more willing to take a punt on a shot.

Mike

Kevin MacDonnell once wrote that he could change the film in a Leica "standing on his head" - this rather foolish statement was taken to task, although not as quickly as it would have been in this forum.

Needless to say, a few issues of "Photography" later, the pictures were published of him accomplishing this deed.

I don't think it's the normal method. It does make changing films in riots seem more plausible though.

John. Would you use centre focus for macro shots. I find that this can affect the overall depth of focus, or am I doing something wrong?

Generally I use manual focus for macro shots as I don't want the camera to try and refocus every time I'm ready to make the exposure. If I do use AF, then I still use centre spot and use the Quick Shift to readjust as I require.

May I mention that you mean Depth of Field, not depth of focus, which is something else entirely. Depth of focus relates to the leeway available in the accurate placement of the sensor or film to make sure the focused image falls on the correct spot.

Depth of Field refers to how much of our picture is sharp from front to back.

Hope that helps!

Cheers mate. Really appreciate that you dropped into my website and had a look. The feedback really keeps me punching on. And thank you once again for the help with regard to this technical issue and everyone else.