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02-11-2007, 01:24 PM   #1
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K/M Lenses, Manual Mode and the Green Button

I've got one of the K10D bodies afflicted with overexposure when using K/M lenses in Manual Mode. Since I virtually never use my K/M lenses, this is not a big deal for me, but - for some reason - it dawned on me today that I haven't seen much about the problem lately so I'm curious: anyone know if this issue has been resolved?

Thanks,

Jer

02-11-2007, 01:36 PM   #2
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Make sure that you set "Using Aperture ring" in "Custom setting" to "permitted" and try again.

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02-11-2007, 02:50 PM   #3
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overexposure for M lenses

QuoteOriginally posted by Sailor Quote
I've got one of the K10D bodies afflicted with overexposure when using K/M lenses in Manual Mode ... anyone know if this issue has been resolved? Jer
Jer:
Not really. Some people have claimed success by swapping the view screen with an istDS, and of course you can apply the math and adjust for the over exposure.
Hopefully a solid solution is in the works ...
02-11-2007, 04:53 PM   #4
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QuoteOriginally posted by alesk Quote
Jer:
Not really. Some people have claimed success by swapping the view screen with an istDS, and of course you can apply the math and adjust for the over exposure.
Hopefully a solid solution is in the works ...
Thanks, Alan. As I said, it's not a big deal. The work around I experimented with works, but is tedious: since my camera overexposes about 1.5 EV after f/4, I use the stop down button and back off 1.5 EV with the front edial.

Jer

02-11-2007, 04:58 PM   #5
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i havnt shot much with my manual lenses (only time was when i was playing around with the reverse mount)

just adjusted settings accordingly to what i want the shot to come out.

great test in general shutter/f-stop relationship..
02-12-2007, 06:26 AM   #6
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QuoteOriginally posted by Sailor Quote
I've got one of the K10D bodies afflicted with overexposure when using K/M lenses in Manual Mode. Since I virtually never use my K/M lenses, this is not a big deal for me, but - for some reason - it dawned on me today that I haven't seen much about the problem lately so I'm curious: anyone know if this issue has been resolved?

Thanks,

Jer
I have not had any problem with exposure on either my K10D or *istD when using the green button in manual mode, both bodies meter perfectly.

The only thing I wish, was that Pentax would use the green button to calculate the number of stops the lens is stopped down, for flash exposure this would permit TTL or P-TTL to work and expand the range of possibilities for older K mount lenses. I have a 300 mmF4 and 400mmF5.6 which I would like to use for wildlife photos, along with a flash, Presently I can't really do this, except that the AF540FGZ does at least have an auto exposure sensor for old style (pre TTL) flash control
02-12-2007, 07:21 AM   #7
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It was heard that someone put a DS screen into the K10D and the problem was resolved. But with original K10D focusing screen, it seems that the issue is yet to be got solved.

It seems that the K10D has not been calibrated properly for the light meter and focusing screen combo when it is stopped down (when doing stopped down metering).

QuoteOriginally posted by Sailor Quote
I've got one of the K10D bodies afflicted with overexposure when using K/M lenses in Manual Mode. Since I virtually never use my K/M lenses, this is not a big deal for me, but - for some reason - it dawned on me today that I haven't seen much about the problem lately so I'm curious: anyone know if this issue has been resolved?

Thanks,

Jer
02-12-2007, 07:47 AM   #8
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QuoteOriginally posted by Lowell Goudge Quote
I have not had any problem with exposure on either my K10D or *istD when using the green button in manual mode, both bodies meter perfectly.

The only thing I wish, was that Pentax would use the green button to calculate the number of stops the lens is stopped down, for flash exposure this would permit TTL or P-TTL to work and expand the range of possibilities for older K mount lenses. I have a 300 mmF4 and 400mmF5.6 which I would like to use for wildlife photos, along with a flash, Presently I can't really do this, except that the AF540FGZ does at least have an auto exposure sensor for old style (pre TTL) flash control
Well Lowell, you kind of open a can of worms here..... So your K10 gives you correct exposures w/ K or M lenses with aperatures set greater than f4??
That sort of complicates the "screen swap thing". WHY would some K10's be good while others are up to 2 stops overexposed?? Can you please verify this does work??? I'm not doubting you per-se but have heard all too often that what was "perfect" was not so. f8 to f10 would be worth a peek.
As to flash TTL is really no problem because flash is calculated at time of exposure as OTF (actually off the sensor). This will compensate for the aperature. p-TTL, on the other hand is useless. another thought is p-TTL also uses distance info (pretty sure on this) from the newer lenses so you need aperature and target distance to make it correct....... Maybe pick up a DS of D for TTL?

02-12-2007, 06:14 PM   #9
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QuoteOriginally posted by jeffkrol Quote
Well Lowell, you kind of open a can of worms here..... So your K10 gives you correct exposures w/ K or M lenses with aperatures set greater than f4??
That sort of complicates the "screen swap thing". WHY would some K10's be good while others are up to 2 stops overexposed?? Can you please verify this does work??? I'm not doubting you per-se but have heard all too often that what was "perfect" was not so. f8 to f10 would be worth a peek.
As to flash TTL is really no problem because flash is calculated at time of exposure as OTF (actually off the sensor). This will compensate for the aperature. p-TTL, on the other hand is useless. another thought is p-TTL also uses distance info (pretty sure on this) from the newer lenses so you need aperature and target distance to make it correct....... Maybe pick up a DS of D for TTL?
Was playing last evening with my 100mm F4 Macro, at several different F Stops and got correct exposure, will check again in a day or two.

Re TTL flash, I did't get correct exposure with the AF500FTZ on the *istD when I tried this previously. I will try again, and let you know.

One further point I have added upon reflection is the way that I use the little green button. I use this when pointing at a neutral object, usually a tree trunk, or asphalt surface as a pseudo grey card to set the exposure, I generally then leave it set as long as the lighting does not radically change. The camera is alwqays in manual mode.

I note some comments here about trying to focus at the same time, Are people trying to use this to do stopped down metering in Av mode??? I have never tried this, and note that if you use K or M lenses in Av mode, the camera always takes the frame at open apature, if you meter stopped down, hold the metering and fire the frame, you will overexpose. Just a thought

Last edited by Lowell Goudge; 02-12-2007 at 06:25 PM. Reason: new comment added
02-12-2007, 06:25 PM   #10
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QuoteOriginally posted by Lowell Goudge Quote
Was playing last evening with my 100mm F4 Macro, at several different F Stops and got correct exposure, will check again in a day or two.

Re TTL flash, I did't get correct exposure with the AF500FTZ on the *istD when I tried this previously. I will try again, and let you know.

One further point I have added upon reflection is the way that I use the little green button. I use this when pointing at a neutral object, usually a tree trunk, or asphalt surface as a pseudo grey card to set the exposure, I generally then leave it set as long as the lighting does not radically change. The camera is alwqays in manual mode.

I note some comments here about trying to focus at the same time, Are people trying to use this to do stopped down metering in Av mode??? I have never tried this, and note that if you use K or M lenses in Av mode, the camera always takes the frame at open apature, if you meter stopped down, hold the metering and fire the frame, you will overexpose. Just a thought
Thanks for the effort...........
02-15-2007, 07:30 AM   #11
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QuoteOriginally posted by jeffkrol Quote
Well Lowell, you kind of open a can of worms here..... So your K10 gives you correct exposures w/ K or M lenses with aperatures set greater than f4??
That sort of complicates the "screen swap thing". WHY would some K10's be good while others are up to 2 stops overexposed?? Can you please verify this does work??? I'm not doubting you per-se but have heard all too often that what was "perfect" was not so. f8 to f10 would be worth a peek.
As to flash TTL is really no problem because flash is calculated at time of exposure as OTF (actually off the sensor). This will compensate for the aperature. p-TTL, on the other hand is useless. another thought is p-TTL also uses distance info (pretty sure on this) from the newer lenses so you need aperature and target distance to make it correct....... Maybe pick up a DS of D for TTL?
As a follow up, now that I am back and reunited with my camera, I took my 100mm SMC-M F 4 macro and ran a series of test shots from F4 all the way to F32 at every detent in the apature ring. The K10 metered correctly and gave good esposure on all shots, until about f22. This is not a problem with the camera exactly, only that I ran out of light, and the camera limits exposure apparently to 1/5 second using the green button. I re-ran the test using my *istD and it performed the same, except that it limited the shutter speed to 1/10 second. Once the shutter speed is limited, obviously the frams under expose. The only potential issue I see here is that it would be nice for the camera to give shutter speeds for ALL exposure settings, up to the minimum shutter speed available, when metering. Perhaps this should go to Pentax as a request.

I will look at flash performance separately
02-15-2007, 08:17 AM   #12
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So that seems to put the K10D manual meter issue into the some have it, some don't catagory. So no GLOBAL disaster. Now back to figuring out why some have issues, and why a
DS focusing screen would solve it. Thanks for keeping up on this.
02-15-2007, 10:14 AM   #13
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QuoteOriginally posted by jeffkrol Quote
So that seems to put the K10D manual meter issue into the some have it, some don't catagory. So no GLOBAL disaster. Now back to figuring out why some have issues, and why a
DS focusing screen would solve it. Thanks for keeping up on this.
Good Questions. The only thing I have not tried yet is to go back to V1.0 of firmware, My tests were with V1.1. One thing I did notice later, is that I was incorrect about the shuttrer speed limitations, what I actually hit was the minimum light limit for the camera, when I go back and look at ISO settings, my K10D was set to 1600, and my *istD was 3200 (I do a lot of low light shots) considering the difference in ISO and minimum shutter speeds, I really did run out of light when I did this test.

In a higher ambient light environment, and lower ISO settings the cameras do give slower shutter speeds.
02-15-2007, 10:43 AM   #14
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QuoteOriginally posted by Lowell Goudge Quote
This is not a problem with the camera exactly, only that I ran out of light, and the camera limits exposure apparently to 1/5 second using the green button. I re-ran the test using my *istD and it performed the same, except that it limited the shutter speed to 1/10 second.
1/5s?
Hmm ..., my K10 goes down to 3s (ISO 1600).
Strange.

Can you see a step up in lightness from f2.8 to f4? With me and several others the exposure is ok up to about f2.8. From f4 on one gets overexposure, at least you can see a break somewhere around f4. No?
02-15-2007, 10:48 AM   #15
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QuoteOriginally posted by jeffkrol Quote
Well Lowell, you kind of open a can of worms here..... So your K10 gives you correct exposures w/ K or M lenses with aperatures set greater than f4??
That sort of complicates the "screen swap thing". WHY would some K10's be good while others are up to 2 stops overexposed?? Can you please verify this does work??? I'm not doubting you per-se but have heard all too often that what was "perfect" was not so. f8 to f10 would be worth a peek.
As to flash TTL is really no problem because flash is calculated at time of exposure as OTF (actually off the sensor). This will compensate for the aperature. p-TTL, on the other hand is useless. another thought is p-TTL also uses distance info (pretty sure on this) from the newer lenses so you need aperature and target distance to make it correct....... Maybe pick up a DS of D for TTL?
I have now had a chance to look at flash exposure.
Using the same 100 mm F 4 Macro lens as I used to confirm correct green button function on my K10, I tried flash exposure.
Using manual mode on my *istD and a 1/150 shutter speed, I again ran a set of pictures from F4 to F32, this time using both the AF540FGZ and AF500FTZ for comparison. The results are surprizing to say the least. While I remember when I first tried flash with manual lenses many years ago, I did not get good results, I must have done something wrong, as I got good results with both flashes on the *istD. Unfortunately the K10 can't meter in TTL and it would be useful if it could somehow use the green button to figure out flash exposure for K&M lenses.
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