auto focus not all its cracked up to be?

reknelb · 06-17-2007, 05:21 PM

I've been messing around alot lately with my m42 lenses on my Samsung gx-1l, and my k10d. Seems like I get about 10-20 percent fewer total shots taken but, my manual shots are focused better. I've experimented with action and still shots. The only draw back to the m42 lenses is that the metering needs to be messed with everytime you change appertures. Long story short, dont give up on your old glass just yet, my 100 dollar m42 is whoopin up on my 900 dollar AF.

*Mike Cash* · 06-17-2007, 05:23 PM

The metering doesn't need to be messed with every time you change apertures. Try shooting in Av mode.

(Can't remember the last time I had an AF lens on my K100D....Takumar rules.)

reknelb · 06-17-2007, 05:43 PM

I actually do use av mode most of the time. I should have said the exposure compensation needs to be messed with when changing apperture. Seems like I have to over-expose except for when I'm wide open, then I have to dial it back. I'm not knocking AF, it worked great on my pheasant hunt. I captured some great action shots. I'm just really starting to like the shots I'm getting out of the old glass. I also should mention it seems like the m42 meters a little better on the Samsung. Which is fine with me, the Sigma 70-200mm has pretty much taken up a permanent residency on the k10d.

**Buddha Jones** · 06-17-2007, 09:11 PM

Originally Posted by reknelb

I've been messing around alot lately with my m42 lenses on my Samsung gx-1l, and my k10d. Seems like I get about 10-20 percent fewer total shots taken but, my manual shots are focused better. I've experimented with action and still shots. The only draw back to the m42 lenses is that the metering needs to be messed with everytime you change appertures. Long story short, dont give up on your old glass just yet, my 100 dollar m42 is whoopin up on my 900 dollar AF.

Well sell me your $900 AF for $200 and somehow you come out ahead, trust me!

keithlester · 06-18-2007, 01:03 AM

Auto-focus has never been as good as a critically sharp eyeball when speed is not important, but it can sure save your a$$ when snapping fast-moving sports action. Horses for courses, I guess. I never had AF until the digital age, and still regularly switch to manual, but I mostly do macro and landscape work, where speed is rarely required.

Jonas B · 06-18-2007, 01:08 AM

Originally Posted by Mike Cash

The metering doesn't need to be messed with every time you change apertures. Try shooting in Av mode.

The OP talks about a K10D. That's a different thing.

*Mike Cash* · 06-18-2007, 02:31 AM

Originally Posted by Jonas B

The OP talks about a K10D. That's a different thing.

You mean the K10D won't set shutter speed in Av mode for M42 lenses, adjusting automatically as the aperture is closed down? Or does the K10D not have an Av mode?

Jonas B · 06-18-2007, 05:58 AM

Originally Posted by Mike Cash

You mean the K10D won't set shutter speed in Av mode for M42 lenses, adjusting automatically as the aperture is closed down? Or does the K10D not have an Av mode?

Oh, yes it will. But you have missed many threads about the exposure errors that was introduced with the k10D. I have posted this diagram a few times, there also are several threads on the matter:

The above is an example. Different lenses make the camera behave different.

regards,

Donald · 06-18-2007, 06:48 PM

I don't understand your graph, is it missing data values on y axis?

jeffkrol · 06-18-2007, 06:55 PM

Originally Posted by Donald

I don't understand your graph, is it missing data values on y axis?

Y axis is deviation from "perfect exposure" (sort of

) ie 0 EV to -/+ ev "off " of zero.
aka exposure "error".......

carpents · 06-18-2007, 06:59 PM

Originally Posted by reknelb

Long story short, dont give up on your old glass just yet, my 100 dollar m42 is whoopin up on my 900 dollar AF.

Me too - I'm sticking with manual focus. Even on my auto-focus lenses.

If it helps, I swapped out the focus screen from my DS (incredibly easy to do) and now my K10 meters more consistently. I had an inverted graph from JonasB - my K10 would gradually overexpose as the aperture got smaller.

*Mike Cash* · 06-19-2007, 02:50 AM

Thanks, Jonas. I understand very well now what you meant. I have largely skipped threads specific to the K10 because I don't have one.

Having seen that graph, I'm glad I don't.

Jonas B · 06-19-2007, 03:05 AM

Originally Posted by Donald

I don't understand your graph, is it missing data values on y axis?

The Y axis is marked (progressive and unorthodoxic) in EV values, at the right side of the diagram strangely enough.

Check the values and you'll get it.

As I'm a bit conservative I have set 0EV (=correct exposure meaning a grey card gives me an RGB value of 97 when developing a raw picture in ACR with all values set to default except of sharpening (0) and curves (straight line).

Some prefer 110 or 125. You can interpret it any way you wish by moving the white lines a bit up or down.

regards,

*borno* · 06-19-2007, 06:29 AM

I mostly have mf lenses and prefer to focus myself seems like part of the picture taking process to me (guess I'm an old dude). It's a little tricky with the plain ground-glass (plastic). My old TLR had a nice pop up magnifier , I might get one for my k10d. As for exposure, I ordered a LL60 *ist screen to try, I wanted a grid anyway and I'm tired of missing bird shots trying to compensate for the exposure (1-1.5 stops over at f8 or f11) those birds won't wait for you

I'm hopeful.

ChrisA · 06-19-2007, 07:45 AM

Originally Posted by Mike Cash

Thanks, Jonas. I understand very well now what you meant. I have largely skipped threads specific to the K10 because I don't have one.

Having seen that graph, I'm glad I don't.

Just to be clear, the exposure errors with old (ie, pre-A) lenses and the K10D have nothing to do with manual-, as opposed to auto-focus.

They arise because it is not possible to set the aperture of pre-A lenses using the body. So the aperture ring on the lens must be used to set the aperture, and then the green button or optical preview lever to get the camera to stop the lens down and meter with the lens stopped down.

It is the metering errors with the K10D (and not, AIUI, with the K100D) in stop-down mode that give rise to the exposure problems.

Use A-series lenses (set to A) or later, MF or AF, and no such errors arise.

It's been suggested in various quarters that with a focusing screen from a DS, the errors go away; if anyone has a K10D with such a screen, and either M/K series lenses, or A lenses that they can switch to non-A mode, it would be interesting to see the line included on Jonas B's graph.