Should K20D overexpose with M lenses?

**Lowell Goudge** · 05-12-2009, 07:53 AM

Originally Posted by Squier
Can you add just +EV compensation when shooting manually ? I have EV bracketing, but by default, i end up with -/0/+ , so always end up with 2/3rds more shots than is necessary

there are issues here,
- first the bracketing using manual apature lenses will be shutter speed only, and you may not wish this.
- second, I am not sure the exposure range of bracketing is wide enough to cover the drift of exposure from -1 to +2 stops
- third, the K10D, unlike the *istD or K20D does not allow EV compensation in manual mode, which would be good enough for old slow lenses, i.e. F5.6 and above, which could be a reasonable work around for long lenses which typically are "slow"

the biggest issue is the under exposure wide open and over exposure stopped down with fast lenses from portrait to wide angle.

fwcetus · 05-12-2009, 08:04 AM

Originally posted by fwcetus

I only wish it ~were~ consistent - it is not. The overexposure is not "linear", in the sense that I'd have to more or less make an exposure compensation curve for each aperture of each K and M lens I have. This could be done, of course, but my original point is that I should not have to. :-(

Originally posted by Canada_Rockies

You are absolutely correct. The exposure error is not the same at each f/stop. My original procedure was to meter at the accurate stop, and then shift the aperture and shutter speed to the equivalent exposure at the aperture I wanted to use. What I have found with the LL-60 is that the exposure is very close to perfect at every f/stop, and I no longer need that tedious step, thank Heaven.

I am glad that the LL-60 is working out for you (and for others). However, I like using my KatzEye split screen so much (and it works reasonably well for exposure on my K20D with any lens with an "A" setting) (and I do have several manual focus A lenses, as well as several later autofocus lenses) that I don't want to lose the manual focus ease I now have. But, it is still annoying to have to "go through hoops" for exposure with some of my older K and M lenses.

Squier · 05-12-2009, 08:07 AM

Thansk Lowell

Well i think the max EV bracket is plus or minus 1 EV ( need to check this ) so i guess anything needing plus 2 will have to be done on shutter, like you say. I may not wish it, but there doesnt seem to be any other way.

Most of my lenses are ' slow ' so no doubt will carry on getting OE. I have a couple of faster lenses - the SMC-A 50mm f1.7 and Panagor f2.8 macro

Thank the heavens for CS4/ Camera Raw

GeneV · 05-12-2009, 01:41 PM

Originally posted by Squier

Time will tell if the korean Focusing.com screen is any better than the chinese versions. I wasnt going to buy a Katz screen at their prices, to find out they're not what i wanted.

Green button metering does not bother me at all, so i wouldnt be messing around drilling holes, but what i want to know is how to add only plus or only minus EV comp. I only seem to be able to bracket rather than set under or over EV comp.

I'm not finding a focusing.com or focusscreens.com. Where are these sold?

I've just had a disappointing experience scratching the Chinese one.

Squier · 05-12-2009, 01:59 PM

Its Focusing Screen

GeneV · 05-12-2009, 03:34 PM

Originally posted by Squier

Its Focusing Screen

Thanks. They have quite a selection.

**Canada_Rockies** · 05-12-2009, 03:39 PM

Originally posted by OregonJim

Have you thought about cleaning the aperture blades? One of my old lenses was slow to stop down due to oil seepage on the blades. An hour or so of fumbling around to get the thing apart, then swabbing the blades with lighter fluid, and it was snappy as new again...

They are not yet slow enough to affect exposure. I will be having the lens repaired this fall, when birding season is over. The tripod shoe no longer holds - the cork or whatever is probably worn out - so it was on the repair list anyway. I do not feel confident about disassembling the lens to repair it myself, but thanks for the hint.

Squier · 05-12-2009, 03:42 PM

Originally posted by GeneV

Thanks. They have quite a selection.

yeah , good place eh

**Canada_Rockies** · 05-12-2009, 03:46 PM

Originally posted by Squier

Time will tell if the korean Focusing.com screen is any better than the chinese versions. I wasnt going to buy a Katz screen at their prices, to find out they're not what i wanted.

Green button metering does not bother me at all, so i wouldnt be messing around drilling holes, but what i want to know is how to add only plus or only minus EV comp. I only seem to be able to bracket rather than set under or over EV comp.

Hi, Squier. To apply only comp one way or the other with the bracketing system, set the EV compensation, then bracket that. For example, if you want to apply only over exposure, and you want it to be applied as 0, +1 and +2, set EV Comp to +1, then bracket 3 at +/- 1 stop. This would give you the results you are looking for. In essence, you are telling the camera with the EV Compensation setting that normal is +1. The bracket will bracket around that value. If you want to set it to +1, +1.5, +2, set +1.5 and 0.5 stop bracket.

Squier · 05-12-2009, 04:05 PM

I can see where you're coming from CR , but i was trying to get away from bracketing, as i really didnt want 2 exta pics every time i snapped a shot off. Mind you, it would be useful for those + 2 over exposures posted here i suppose.

But as said , if i dont want 2 extra pics from bracketing everytime i take a shot, i'll have to compensate with shutter speed instead

OregonJim · 05-12-2009, 04:11 PM

Originally posted by Canada_Rockies

They are not yet slow enough to affect exposure. I will be having the lens repaired this fall, when birding season is over. The tripod shoe no longer holds - the cork or whatever is probably worn out - so it was on the repair list anyway. I do not feel confident about disassembling the lens to repair it myself, but thanks for the hint.

Yes, I totally understand waiting for birding season to end.

chhayanat · 05-25-2009, 05:47 AM

Canada Rockies successfully replaced the focussing screen on a K10D with an LL-60 screen. In post 23 I had assumed with unwarranted overconfidence that fitting an LL-60 on a Samsung GX20 should be possiblle in view of the great similarity with the K20D which has interchangeable focussing screens. Now I am having cold feet: the GX20 manual says nothing about interchangeable focussing screens. Has anyone fitted an alternative focussing screen on a GX20? Would be useful to know.

**Canada_Rockies** · 05-25-2009, 08:36 AM

Originally posted by chhayanat

Canada Rockies successfully replaced the focussing screen on a K10D with an LL-60 screen. In post 23 I had assumed with unwarranted overconfidence that fitting an LL-60 on a Samsung GX20 should be possiblle in view of the great similarity with the K20D which has interchangeable focussing screens. Now I am having cold feet: the GX20 manual says nothing about interchangeable focussing screens. Has anyone fitted an alternative focussing screen on a GX20? Would be useful to know.

Look in your manual for the "Optional Accessories" list. There is nothing in my K10 manual about interchangeable focusing screens, but they are listed on those pages. If I had to bet money on it, I would bet that you do have interchangeable screens.

chhayanat · 05-25-2009, 12:03 PM

Originally posted by Canada_Rockies

Look in your manual for the "Optional Accessories" list. There is nothing in my K10 manual about interchangeable focusing screens, but they are listed on those pages. If I had to bet money on it, I would bet that you do have interchangeable screens.

I looked at the manual again. Under Optional Accessories it has nothing listed apart from the flash, the camera case and some parts which are packed with the camera.

There is, however, the encouraging phrase: "Dedicated accessories are available for this camera. Please contact a service centre for details regarding accessories."
Now to find this rare beastie, a dedicated service centre. Korea is strong in Romania. So all hope is not yet lost.
Thanks Canada Rockies.

johnmflores · 05-29-2009, 09:23 AM

Originally posted by Canada_Rockies

They are not yet slow enough to affect exposure. I will be having the lens repaired this fall, when birding season is over. The tripod shoe no longer holds - the cork or whatever is probably worn out - so it was on the repair list anyway. I do not feel confident about disassembling the lens to repair it myself, but thanks for the hint.

I've just diagnosed this as the problem with my M 50/1.7 - slow aperture blades. As you noted earlier, the green button doesn't stop down the lens long enough for the aperture blades to close down to their set position, thus throwing off the metering.

DOF preview gives you the ability to stop down the lens and keep it stopped down to get an accurate reading, but what's happening with mine is that when the actual shot is taken the lens isn't stopped down to it's set level, Thus the overexposure.

In other words....

In a perfect world, when you press the shutter release, the following happens in rapid sequence:

1 - lens is stopped down to desired aperture (say F8.0 for this example)
2 - mirror flips up
3 - exposure
4 - mirror flips down
5 - lens is opened

What's happening in my case is that Step 1 is taking too long (if at all) and overlapping with the other steps. If my aperture blades are so slow that the lens is only stopped down to F4.0 by the time the camera gets to Step 3, then the resulting image will be overexposed by approximately 2 stops.

It's also easy to see how this can affect setting the proper exposure, and why the results become even less satisfactory/predictable as the aperture is set smaller. At wide open the problem doesn't exist, but at F22 the "lazy aperture" problem is most pronounced because the delay is most pronounced.

There's a sure fire way to determine if you've got "lazy aperture":

A - Create a repeatable situation where the camera is consistently overexposing with the Green Button exposure method.

B - Set your exposure by the DOF Preview/Needle Matching method. This is the most reliable way since it gives your lazy blades enough time to stop down. Note if this gives you a different shutter speed.

C - Set the timer to a 2 second delay and take the same shot. This delay gives the camera an extra 2 seconds to complete steps 1 and 2 above. If the resulting shot is properly exposed, than you probably have "lazy aperture".

A quick way to diagnose the problem is to set a small aperture (F22) and then look directly into the lens as you take a shot. You might be surprised, as I was to see the blades not come stop down at all at faster shutter speeds.

Time to take out the small screwdrivers and dissect the 50mm/1.7 tonight...

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05-12-2009, 07:53 AM	#46
Lowell Goudge Site Supporter Join Date: Jan 2007 Location: Toronto Photos: Gallery \| Albums Posts: 17,886	Originally Posted by Squier Can you add just +EV compensation when shooting manually ? I have EV bracketing, but by default, i end up with -/0/+ , so always end up with 2/3rds more shots than is necessary there are issues here, - first the bracketing using manual apature lenses will be shutter speed only, and you may not wish this. - second, I am not sure the exposure range of bracketing is wide enough to cover the drift of exposure from -1 to +2 stops - third, the K10D, unlike the *istD or K20D does not allow EV compensation in manual mode, which would be good enough for old slow lenses, i.e. F5.6 and above, which could be a reasonable work around for long lenses which typically are "slow" the biggest issue is the under exposure wide open and over exposure stopped down with fast lenses from portrait to wide angle.

05-12-2009, 08:04 AM	#47
fwcetus Site Supporter Join Date: Sep 2006 Location: New England Photos: Gallery \| Albums Posts: 1,286	Originally posted by fwcetus I only wish it ~were~ consistent - it is not. The overexposure is not "linear", in the sense that I'd have to more or less make an exposure compensation curve for each aperture of each K and M lens I have. This could be done, of course, but my original point is that I should not have to. :-( Originally posted by Canada_Rockies You are absolutely correct. The exposure error is not the same at each f/stop. My original procedure was to meter at the accurate stop, and then shift the aperture and shutter speed to the equivalent exposure at the aperture I wanted to use. What I have found with the LL-60 is that the exposure is very close to perfect at every f/stop, and I no longer need that tedious step, thank Heaven. I am glad that the LL-60 is working out for you (and for others). However, I like using my KatzEye split screen so much (and it works reasonably well for exposure on my K20D with any lens with an "A" setting) (and I do have several manual focus A lenses, as well as several later autofocus lenses) that I don't want to lose the manual focus ease I now have. But, it is still annoying to have to "go through hoops" for exposure with some of my older K and M lenses.

05-12-2009, 08:07 AM	#48
Squier Veteran Member Join Date: Apr 2009 Location: Oxfordshire UK Photos: Albums Posts: 706	Thansk Lowell Well i think the max EV bracket is plus or minus 1 EV ( need to check this ) so i guess anything needing plus 2 will have to be done on shutter, like you say. I may not wish it, but there doesnt seem to be any other way. Most of my lenses are ' slow ' so no doubt will carry on getting OE. I have a couple of faster lenses - the SMC-A 50mm f1.7 and Panagor f2.8 macro Thank the heavens for CS4/ Camera Raw

05-12-2009, 01:41 PM	#49
GeneV Veteran Member Join Date: Oct 2008 Location: Albuquerque NM Photos: Albums Posts: 9,830	Originally posted by Squier Time will tell if the korean Focusing.com screen is any better than the chinese versions. I wasnt going to buy a Katz screen at their prices, to find out they're not what i wanted. Green button metering does not bother me at all, so i wouldnt be messing around drilling holes, but what i want to know is how to add only plus or only minus EV comp. I only seem to be able to bracket rather than set under or over EV comp. I'm not finding a focusing.com or focusscreens.com. Where are these sold? I've just had a disappointing experience scratching the Chinese one.

05-12-2009, 01:59 PM	#50
Squier Veteran Member Join Date: Apr 2009 Location: Oxfordshire UK Photos: Albums Posts: 706	Its Focusing Screen

05-12-2009, 03:34 PM	#51
GeneV Veteran Member Join Date: Oct 2008 Location: Albuquerque NM Photos: Albums Posts: 9,830	Originally posted by Squier Its Focusing Screen Thanks. They have quite a selection.

05-12-2009, 03:39 PM	#52
Canada_Rockies Loyal Site Supporter Join Date: Nov 2007 Location: Sparwood, BC, Canada Photos: Gallery \| Albums Posts: 12,385	Originally posted by OregonJim Have you thought about cleaning the aperture blades? One of my old lenses was slow to stop down due to oil seepage on the blades. An hour or so of fumbling around to get the thing apart, then swabbing the blades with lighter fluid, and it was snappy as new again... They are not yet slow enough to affect exposure. I will be having the lens repaired this fall, when birding season is over. The tripod shoe no longer holds - the cork or whatever is probably worn out - so it was on the repair list anyway. I do not feel confident about disassembling the lens to repair it myself, but thanks for the hint.

05-12-2009, 03:42 PM	#53
Squier Veteran Member Join Date: Apr 2009 Location: Oxfordshire UK Photos: Albums Posts: 706	Originally posted by GeneV Thanks. They have quite a selection. yeah , good place eh

05-12-2009, 03:46 PM	#54
Canada_Rockies Loyal Site Supporter Join Date: Nov 2007 Location: Sparwood, BC, Canada Photos: Gallery \| Albums Posts: 12,385	Originally posted by Squier Time will tell if the korean Focusing.com screen is any better than the chinese versions. I wasnt going to buy a Katz screen at their prices, to find out they're not what i wanted. Green button metering does not bother me at all, so i wouldnt be messing around drilling holes, but what i want to know is how to add only plus or only minus EV comp. I only seem to be able to bracket rather than set under or over EV comp. Hi, Squier. To apply only comp one way or the other with the bracketing system, set the EV compensation, then bracket that. For example, if you want to apply only over exposure, and you want it to be applied as 0, +1 and +2, set EV Comp to +1, then bracket 3 at +/- 1 stop. This would give you the results you are looking for. In essence, you are telling the camera with the EV Compensation setting that normal is +1. The bracket will bracket around that value. If you want to set it to +1, +1.5, +2, set +1.5 and 0.5 stop bracket.

05-12-2009, 04:05 PM	#55
Squier Veteran Member Join Date: Apr 2009 Location: Oxfordshire UK Photos: Albums Posts: 706	I can see where you're coming from CR , but i was trying to get away from bracketing, as i really didnt want 2 exta pics every time i snapped a shot off. Mind you, it would be useful for those + 2 over exposures posted here i suppose. But as said , if i dont want 2 extra pics from bracketing everytime i take a shot, i'll have to compensate with shutter speed instead

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05-12-2009, 04:11 PM	#56
OregonJim Veteran Member Join Date: Mar 2009 Location: Willamette Valley, Oregon Posts: 1,327	Originally posted by Canada_Rockies They are not yet slow enough to affect exposure. I will be having the lens repaired this fall, when birding season is over. The tripod shoe no longer holds - the cork or whatever is probably worn out - so it was on the repair list anyway. I do not feel confident about disassembling the lens to repair it myself, but thanks for the hint. Yes, I totally understand waiting for birding season to end.

05-25-2009, 05:47 AM	#57
chhayanat Senior Member Join Date: Nov 2008 Location: The Cow Belt Photos: Gallery Posts: 173	Canada Rockies successfully replaced the focussing screen on a K10D with an LL-60 screen. In post 23 I had assumed with unwarranted overconfidence that fitting an LL-60 on a Samsung GX20 should be possiblle in view of the great similarity with the K20D which has interchangeable focussing screens. Now I am having cold feet: the GX20 manual says nothing about interchangeable focussing screens. Has anyone fitted an alternative focussing screen on a GX20? Would be useful to know.

05-25-2009, 08:36 AM	#58
Canada_Rockies Loyal Site Supporter Join Date: Nov 2007 Location: Sparwood, BC, Canada Photos: Gallery \| Albums Posts: 12,385	Originally posted by chhayanat Canada Rockies successfully replaced the focussing screen on a K10D with an LL-60 screen. In post 23 I had assumed with unwarranted overconfidence that fitting an LL-60 on a Samsung GX20 should be possiblle in view of the great similarity with the K20D which has interchangeable focussing screens. Now I am having cold feet: the GX20 manual says nothing about interchangeable focussing screens. Has anyone fitted an alternative focussing screen on a GX20? Would be useful to know. Look in your manual for the "Optional Accessories" list. There is nothing in my K10 manual about interchangeable focusing screens, but they are listed on those pages. If I had to bet money on it, I would bet that you do have interchangeable screens.

05-25-2009, 12:03 PM	#59
chhayanat Senior Member Join Date: Nov 2008 Location: The Cow Belt Photos: Gallery Posts: 173	Originally posted by Canada_Rockies Look in your manual for the "Optional Accessories" list. There is nothing in my K10 manual about interchangeable focusing screens, but they are listed on those pages. If I had to bet money on it, I would bet that you do have interchangeable screens. I looked at the manual again. Under Optional Accessories it has nothing listed apart from the flash, the camera case and some parts which are packed with the camera. There is, however, the encouraging phrase: "Dedicated accessories are available for this camera. Please contact a service centre for details regarding accessories." Now to find this rare beastie, a dedicated service centre. Korea is strong in Romania. So all hope is not yet lost. Thanks Canada Rockies.

05-29-2009, 09:23 AM	#60
johnmflores Veteran Member Join Date: Apr 2009 Location: Somerville, NJ Photos: Gallery \| Albums Posts: 5,361	Originally posted by Canada_Rockies They are not yet slow enough to affect exposure. I will be having the lens repaired this fall, when birding season is over. The tripod shoe no longer holds - the cork or whatever is probably worn out - so it was on the repair list anyway. I do not feel confident about disassembling the lens to repair it myself, but thanks for the hint. I've just diagnosed this as the problem with my M 50/1.7 - slow aperture blades. As you noted earlier, the green button doesn't stop down the lens long enough for the aperture blades to close down to their set position, thus throwing off the metering. DOF preview gives you the ability to stop down the lens and keep it stopped down to get an accurate reading, but what's happening with mine is that when the actual shot is taken the lens isn't stopped down to it's set level, Thus the overexposure. In other words.... In a perfect world, when you press the shutter release, the following happens in rapid sequence: 1 - lens is stopped down to desired aperture (say F8.0 for this example) 2 - mirror flips up 3 - exposure 4 - mirror flips down 5 - lens is opened What's happening in my case is that Step 1 is taking too long (if at all) and overlapping with the other steps. If my aperture blades are so slow that the lens is only stopped down to F4.0 by the time the camera gets to Step 3, then the resulting image will be overexposed by approximately 2 stops. It's also easy to see how this can affect setting the proper exposure, and why the results become even less satisfactory/predictable as the aperture is set smaller. At wide open the problem doesn't exist, but at F22 the "lazy aperture" problem is most pronounced because the delay is most pronounced. There's a sure fire way to determine if you've got "lazy aperture": A - Create a repeatable situation where the camera is consistently overexposing with the Green Button exposure method. B - Set your exposure by the DOF Preview/Needle Matching method. This is the most reliable way since it gives your lazy blades enough time to stop down. Note if this gives you a different shutter speed. C - Set the timer to a 2 second delay and take the same shot. This delay gives the camera an extra 2 seconds to complete steps 1 and 2 above. If the resulting shot is properly exposed, than you probably have "lazy aperture". A quick way to diagnose the problem is to set a small aperture (F22) and then look directly into the lens as you take a shot. You might be surprised, as I was to see the blades not come stop down at all at faster shutter speeds. Time to take out the small screwdrivers and dissect the 50mm/1.7 tonight...