[robert]

After reading all the problems with under exposure and over exposure using the k10d and old m lenses I thought I'd check my fairly new k10 d with the only 2 old lens a 135 2.5 takumar and a m135 3.5 smc lens.I took several different shots at each aperture using the green button and I can honestly say the exposure is more accurate with them than it is with my kit lens and my f 50 1.7. Both the newer lens constantly under expose and I have to use exposure compensation.We are told that is to keep from blowing highlights which I think is a bunch of baloney. My 2 older lens meter pretty accurately according to the way they look and the histogram....Bob

[Lowell Goudge]

take a series of shots from F2.5 to F32 with the 135 F2.5 lens, using green button to expose each one.

sample subject should be block wall or paved road.

give the histogram value from a photo editor for each shot, vs f stop and tell me then what you think.

note the histogram should be between 110 and 120 for perfectly exposed shot.

[Stratman]

Hmm, my experience has been the exact opposite with "M" lenses, at large apertures < Under F 4 > I get underexposure, Above F 5.6, I get Overexposure. Maybe the newer revision K10s meter better wit the green button, I sure wish mine did !!

[robert]

Most people seem to have more trouble with apertures over 5.6 overexposing here is an example of a shot from my m135 3.5 taken at f5.6 f8 f11 and f16. I have more if you'd like to see..Bob

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Last edited by robert; 04-30-2008 at 08:36 AM.

[robert]

My manual focusing isn't so hot but I was in a hurry and wanted more to show the exposure...Bob

[stevebrot]

Hmm, my experience has been the exact opposite with "M" lenses, at large apertures < Under F 4 > I get underexposure, Above F 5.6, I get Overexposure. Maybe the newer revision K10s meter better wit the green button, I sure wish mine did !!

My experience is similar for all non-A lenses. For large apertures (under f/5.6), I get underexposure (about 2 stops at f/2). For smaller apertures, (over f/11), I get overexposure (about 1 stop at f/22). The easiest way to visibly assess the shift is to make an exposure series against a well-lit painted white wall.

To do:

1. Set your lens at its smallest aperture
2. Use the green button to determine the shutter speed and do an exposure
3. Turn the aperture ring one click and repeat step 2 until the lens is wide open
4. Push the preview button to display the last picture on the camera's lcd
5. Turn the back scroll wheel (thumb) to the left to show the whole series at a glance

A proper exposures in the series should be about the same value as the 18% gray card.

Cheers!

Steve

[Stratman]

My manual focusing isn't so hot but I was in a hurry and wanted more to show the exposure...Bob

I would say that the F5.6 shot is the best exposed of the bunch, the rest look to me like they are a bit overexposed, BUT, not as bad as they would be on MY K10D, lol

[stevebrot]

Strangely enough, I just did the green button exposure series on my brand-new Pentax-FA 35mm f/2 and it showed the same over/under exposure pattern as my m-series and m-42 lenses.

When I also did the series with my A 50mm f/1.7 and almost new Sigma 50mm f/2.8 Macro, both extremes were underexposed.

With my Tamron 70-150 (adaptall-2, PK-A) wide is underexposed, but all others are just fine.

Ummmmm...I guess that means that green button is essentially a guessing game at extremes for aperture, regardless of the generation of lenses.

I think that there may be more to the the stop-down meter story then the generation of lens.

[Lowell Goudge]

Robert

I hate to disappoint you but if I take the greyscale value off the shed i get the following

f5.6- 161
f8 - 184
f11 - 201
f16 - 199

Note a change of 40 is one stop.

if you did the same shot with the same metering point at f3.5 I would bet it would be at about 120.

your metering is just as far off as everyone elses.

I have tested the metering of my K10D with all 8 manual lenses, and have begun with my new AE lenses (but in both AE and Manual mode.

It is not just old lenses, but any lens in manual mode

[Canada_Rockies]

Robert

I hate to disappoint you but if I take the greyscale value off the shed i get the following

f5.6- 161
f8 - 184
f11 - 201
f16 - 199

Note a change of 40 is one stop.

if you did the same shot with the same metering point at f3.5 I would bet it would be at about 120.

your metering is just as far off as everyone elses.

I have tested the metering of my K10D with all 8 manual lenses, and have begun with my new AE lenses (but in both AE and Manual mode.

It is not just old lenses, but any lens in manual mode

to add to Lowell's comment, I have the same problem of exposure with my M lenses as the rest of the crowd. My solution to the system is to find the apertures at which my lenses meter correctly, and use those apertures for metering. If I am in a hurry for the shots, I will use those apertures, if I have time to do it, I can interpolate.

What I found is that once I have found an accurate metering aperture, I can interpolate from there and get perfect exposures. It is definitely a metering problem rather than a mechanical problem with the stop down lever. (At least with my two lenses)

[robert]

I admit the pictures lighten at the smaller aperatures but nothing I can't adjust in lightroom...Bob

[Lowell Goudge]

I admit the pictures lighten at the smaller aperatures but nothing I can't adjust in lightroom...Bob

Maybe I'm just being completely thick, or stuborn, but my approach is to not usepost processing as a standard part of my workflow.

maybe it is naive on my part, to believe the camera should be capable of taking a shot correctly, and that except for unusual crops, the image should come out of the camera correctly.

I don't consider a 1 stop correction, or in many cases a 2 stop correction as acceptable, in terms of what today's technology can do.

While I understand the approach of Canadian Rockies, if I wanted to have to basically meter the light and then set shutter and apature completely manually, I would have bought a light meter.

Is it just me and some dumb expectation that a modern camera should do things at least as well as the pentax spotmatic did in the early 1970's? Or worse still, that the K10D with all its other advantages and sophistication, can't do this one basic function as well as pentax's first DSLR, the *istD.

[robert]

Lowell...I know what you mean. It took me the longest time to realize if I shhot a landscape with just a small part of the sky in the frame I have to adjust exposure compensation or my photo will be under exposed. They say this is done on purpose to keep from blowing highlights. I don't really buy it....Bob

[kittykat46]

The strength and also weakness of Pentax is it can work will all the legacy lenses going back a long way. The body may be able to communicate and function with the older lenses, but that doesn't mean its perfectly compatible.

If it won't meter very accurately with some of the old lenses, I guess that's a compromise we have to accept.

Anyway there's no comparison with the competition. Nikon, Canon etc. simply won't work with most of Their old legacy lenses.

[stevebrot]

...Is it just me and some dumb expectation that a modern camera should do things at least as well as the pentax spotmatic did in the early 1970's?...

I am with Lowell. Stop-down metering used to be the gold standard. In the late 60's and early 70's, if a through-the-lens meter displayed these characteristics, the body would be deemed unacceptable.

Steve