[RioRico]

Just a point of clarification -- I can use Av mode with K-mount M lenses -- it's just that it'll always be stuck at the widest aperture, right?

Right. With a K-A lens, you can set the aperture ring to A and proceed merrily in any mode except M. With a K-M lens, you must be in M mode for your aperture setting to work. (Hit the Green button to stop down to see your shutter speed.) Outside of M-mode, you're wide open.

And it looks like I need to get an adapter ring to use M42 lenses. Are there any "A" M42 lenses, or are they all manual? And when you say you can use M42 lenses in Av mode, that means the settings on the aperture ring will be recognized by the K-x in Av mode, right?

Ah, M42 (and the few M39) lenses are another story. Some are A(uto), but only on M42 bodies. Some are A(uto) ONLY and must be tweaked to set f-stops on Pentax K-mount (PK) bodies. Some have an A/M switch; set the switch to M, and you can set the f-stop and shoot happily in Av mode. Some are M(anual) only, and may or may not have preset aperture rings. All M39 lenses are like that. These also work fine in Av.

M42's that are A(uto) on M42 bodies have a little pin in their lens mount. When the pin is out, the iris is open. When the pin is pressed in, the iris shuts to the f-stop you set. The M/A switch set to M(anual) pulls that pin in and closes the iris. Without a M/A switch, you need to glue or tape the pin in -- but if it's glued in, it won't work on M42 bodies any more (as I have learned the hard way). But on your dSLR you can shoot in Av mode.

That's the overview. I'm sure some gruesome details will emerge. Stay tuned.

[sjwoo]

Right. With a K-A lens, you can set the aperture ring to A and proceed merrily in any mode except M. With a K-M lens, you must be in M mode for your aperture setting to work. (Hit the Green button to stop down to see your shutter speed.) Outside of M-mode, you're wide open.



Ah, M42 (and the few M39) lenses are another story. Some are A(uto), but only on M42 bodies. Some are A(uto) ONLY and must be tweaked to set f-stops on Pentax K-mount (PK) bodies. Some have an A/M switch; set the switch to M, and you can set the f-stop and shoot happily in Av mode. Some are M(anual) only, and may or may not have preset aperture rings. All M39 lenses are like that. These also work fine in Av.

M42's that are A(uto) on M42 bodies have a little pin in their lens mount. When the pin is out, the iris is open. When the pin is pressed in, the iris shuts to the f-stop you set. The M/A switch set to M(anual) pulls that pin in and closes the iris. Without a M/A switch, you need to glue or tape the pin in -- but if it's glued in, it won't work on M42 bodies any more (as I have learned the hard way). But on your dSLR you can shoot in Av mode.

That's the overview. I'm sure some gruesome details will emerge. Stay tuned.

I think I may stay away from those M42 lenses until I get a better handle on just these manual Pentaxes...!

The sun's back out, and when I point the Sears lens in M mode at the sky, shutter speed reports 0.3" after spot down metering. This isn't a bum lens, is it?

- Sung

[Ira]

Just a point of clarification -- I can use Av mode with K-mount M lenses -- it's just that it'll always be stuck at the widest aperture, right?

And it looks like I need to get an adapter ring to use M42 lenses. Are there any "A" M42 lenses, or are they all manual? And when you say you can use M42 lenses in Av mode, that means the settings on the aperture ring will be recognized by the K-x in Av mode, right?

Thanks for all your help...

- Sung

Get the official Pentax adapter so you're ready when you get the cojones or find a great M42 bargain.

[Hemi345]

I think I may stay away from those M42 lenses until I get a better handle on just these manual Pentaxes...!

The sun's back out, and when I point the Sears lens in M mode at the sky, shutter speed reports 0.3" after spot down metering. This isn't a bum lens, is it?

- Sung

No, not a bum lens. My Auto Rikenon 55mm f/1.4 (M42) does the same thing occasionally when wide open and out in bright sunlight and metering on a light colored object. The only thing I can think of why it does this is because 1/6000 isn't fast enough so the camera reverts to 0.3". If I pick something a little darker, it'll set the shutter to 1/5000 or 1/6000. Maybe someone will reply why it does that.

And when you say you can use M42 lenses in Av mode, that means the settings on the aperture ring will be recognized by the K-x in Av mode, right?

If you mean the camera will know what aperture the lens is set at, I don't think it does. The aperture ring setting on mine isn't recognized by the camera, atleast according to EXIF data... it always says "f/0" even when the mode is set to Av.

[RioRico]

I think I may stay away from those M42 lenses until I get a better handle on just these manual Pentaxes...!

Hey, most M42's are no problem. Those with an A/M switch, or no pin, work like a charm. They're actually easier to operate than manual K-M lenses. We have ongoing debates over which adapters to use -- I use them all.

The sun's back out, and when I point the Sears lens in M mode at the sky, shutter speed reports 0.3" after spot down metering. This isn't a bum lens, is it?

Hmm, that doesn't sound so good. Try this: remove lens from camera. Twist aperture ring while looking into lens. Does the iris open and close? It should. Set aperture to f/16. Push on the f-stop flag (actuator) on the lens base. Does the iris open? It should. If not, you've got a wide-open lens.

[RioRico]

And when you say you can use M42 lenses in Av mode, that means the settings on the aperture ring will be recognized by the K-x in Av mode, right?

If you mean the camera will know what aperture the lens is set at, I don't think it does. The aperture ring setting on mine isn't recognized by the camera, atleast according to EXIF data... it always says "f/0" even when the mode is set to Av.

The camera doesn't know or care what the aperture is. It just sees the amount of light coming in at that f-stop, then calculates the exposure. You can even set ISO to AUTO and let the cam try to optimize everything. The EXIF data will contain the ISO and shutter speed, but not the f-stop.

[Hemi345]

The camera doesn't know or care what the aperture is. It just sees the amount of light coming in at that f-stop, then calculates the exposure. You can even set ISO to AUTO and let the cam try to optimize everything. The EXIF data will contain the ISO and shutter speed, but not the f-stop.

So that's probably why folks are saying they have to use exposure compensation when using Av mode. The times I've tried using my lens in Av mode, the pictures are usually severely underexposed or occasionally overexposed. I found it easier to use (M)anual mode and hit the green button before taking the shot.

[sjwoo]

No, not a bum lens. My Auto Rikenon 55mm f/1.4 (M42) does the same thing occasionally when wide open and out in bright sunlight and metering on a light colored object. The only thing I can think of why it does this is because 1/6000 isn't fast enough so the camera reverts to 0.3". If I pick something a little darker, it'll set the shutter to 1/5000 or 1/6000. Maybe someone will reply why it does that.



If you mean the camera will know what aperture the lens is set at, I don't think it does. The aperture ring setting on mine isn't recognized by the camera, atleast according to EXIF data... it always says "f/0" even when the mode is set to Av.

Thanks, Hemi345. That's exactly what happens to my Sears lens -- I guess the sensor is unable to handle it when it's that bright. My plan was to shoot this lens at its widest aperture just about all the time, but it looks like I won't be able to do that. I shot some shots in daylight at 1/6000, and some of them were severely overexposed.

- Sung

[sjwoo]

Hmm, that doesn't sound so good. Try this: remove lens from camera. Twist aperture ring while looking into lens. Does the iris open and close? It should. Set aperture to f/16. Push on the f-stop flag (actuator) on the lens base. Does the iris open? It should. If not, you've got a wide-open lens.

Yes to both, so I think the lens is AOK. I took some shots at f8, and they came out quite nicely. I guess the metering is just trying to tell me that I shouldn't attempt to take a shot it's not able to read!

I'm so glad I got this manual lens -- now I'm gonna get me a 135mm!

- Sung

[Ira]

So that's probably why folks are saying they have to use exposure compensation when using Av mode. The times I've tried using my lens in Av mode, the pictures are usually severely underexposed or occasionally overexposed. I found it easier to use (M)anual mode and hit the green button before taking the shot.

Exactly what happens to me, so Av mode seems to be worthless if I can use M and just hit that button.

And another thing:

None of my Taks supply focus confirmation on my kx at minimum aperture. Anyone with similar experiences?

[RioRico]

None of my Taks supply focus confirmation on my kx at minimum aperture. Anyone with similar experiences?

It probably means you're being bad and shouldn't try to shoot at f/22.

Hmm, I just put a Super-Tak 55/2 on my K20D and went to the edge, f/16. Nope. At f/11. Nope. At f/8. Yep. At f/9.6. Nope. There's a wall there. Could it be that the DOF is so great that the poor little CPU can't tell when we've passed the threshold between dull and sharp?

[Hemi345]

That's interesting. I've never tried shooting mine at anything smaller than f/8. I'll have to see what the limit on mine is

[Ira]

I'll check this again, but I'm like 99% sure:

All Super-Taks--50 1.4, 55 1.8, 105 2.8--and they're all fine with confirmation at all apertures except their smallest.

Somewhere in my house is my 135, and I really have to find that thing!

[aleonx3]

I'll check this again, but I'm like 99% sure:

All Super-Taks--50 1.4, 55 1.8, 105 2.8--and they're all fine with confirmation at all apertures except their smallest.

Somewhere in my house is my 135, and I really have to find that thing!

Ira, I like to know too. Two things that come to mind for this issue - could it be focusing when the aperture is smallest is difficult because of available light? How do you do it? The method I use is to focus first with the aperture wide open, and then change the aperture - start counting as I turn the aperture ring, and then I hit the green button to get the proper shutter speed - then press the shutter release.

I have had some MF lens that I am not able to focus to infinity; but after adjusting and re-aligning the focus ring so that it can focus beyond infinity, then it works fine. Could this be the case with yours?

[sjwoo]

The reason why my Sears lens was unable to stop down meter properly was because of ISO, too. I had it on 1600! Once I brought it down to 200, I was able to stop down meter just fine in plenty of sunlight at f1.7 (shutter speed was still very fast, though, either 2000 or 4000). I forgot that in M mode, the ISO doesn't float...