old m lens on dslr

Barry_S · 12-25-2008, 03:57 PM

I've using Pentax for 30 years and have a lot of M lens. I received a K20D. Changed setting to permitted aperture lens. Set to AV mode. But the shutter speed read the same, 1/90 at f1.7 or f22. I'm missing something and not sure what. The manual don't tell you much.
After messing with it abit, it seems to me that it locks the aperture open and you loss all control. If so how do you adjust the aperture and shutter speed.
Thanks

Marc Sabatella · 12-25-2008, 04:00 PM

Av mode doesn't work with manual lenses (unless they have an "A" position on the aperture ring and you use that). Use "M" mode and hit the Green button to get the camera to temporarily stop down, take a meter reading, and set a shutter speed for you. Use DOF preview to view the meter reading live.

Barry_S · 12-25-2008, 05:37 PM

Have any tips on using flash in m mode also

Marc Sabatella · 12-25-2008, 10:02 PM

Flash fires full power with manual lenses, you you need to use the old guide number formula: divide the flash guide number by the distance to subject to get the proper aperture, and then set the aperture to that value. It's how they did it in the old days...

denisv · 12-26-2008, 01:08 AM

Do any of the auto modes work with preset lenses?

elkarrde · 12-26-2008, 02:54 AM

Originally posted by Barry_S

I've using Pentax for 30 years and have a lot of M lens. I received a K20D. Changed setting to permitted aperture lens. Set to AV mode. But the shutter speed read the same, 1/90 at f1.7 or f22. I'm missing something and not sure what. The manual don't tell you much.
After messing with it abit, it seems to me that it locks the aperture open and you loss all control. If so how do you adjust the aperture and shutter speed.
Thanks

yes, when your camera is not in M mode, the lens stays constantly wide-open.
switch to M mode, close the aperture, hit the green button - voila! stop-down metering.

Big Dave · 12-26-2008, 08:35 AM

denisy,
Older lenses with auto diapharm work in manual mode, those without auto diapharm will work fine in AV or manual. With smaller M type lenses, you can mount them and then rotate them counter clockwise about ten degrees to allow AV operation. All of the M42 lenses work in AV, because the auto diapharm isn't connected to the camera. They must have a manual/auto switch on the lens set to manual for this, or be locked in manual. By locked in manual, I meanthat the actuator pin must be permenantly depressed.

Dave

Originally posted by denisv

Do any of the auto modes work with preset lenses?

newarts · 12-26-2008, 08:47 AM

Originally posted by Big Dave

denisy,
Older lenses with auto diapharm work in manual mode, those without auto diapharm will work fine in AV or manual. With smaller M type lenses, you can mount them and then rotate them counter clockwise about ten degrees to allow AV operation. All of the M42 lenses work in AV, because the auto diaphram isn't connected to the camera. They must have a manual/auto switch on the lens set to manual for this, or be locked in manual. By locked in manual, I mean that the actuator pin must be permenantly depressed.

Dave

At least with a K100D, the electrical contacts on the camera's flange need to be shorted electrically to insure proper exposure metering and "focus trapping" mode.

Some use a piece of aluminum foil to do this; after doing so to prove to myself its necessity, I sanded some paint off the lens' base to make the electrical contact.

Dave

George Lama · 12-27-2008, 12:43 AM

With the K10 and my M lenses, since you can't redirect/diffuse the on-body flash as readily, I've had much better results with off-camera flashes, both with an old Focal manual and a new Promaster Digital in Manual mode.

12-25-2008, 03:57 PM	#1
Barry_S Forum Member Join Date: Dec 2008 Location: ohio Posts: 64	old m lens on dslr I've using Pentax for 30 years and have a lot of M lens. I received a K20D. Changed setting to permitted aperture lens. Set to AV mode. But the shutter speed read the same, 1/90 at f1.7 or f22. I'm missing something and not sure what. The manual don't tell you much. After messing with it abit, it seems to me that it locks the aperture open and you loss all control. If so how do you adjust the aperture and shutter speed. Thanks

12-25-2008, 05:37 PM	#3
Barry_S Forum Member Join Date: Dec 2008 Location: ohio Posts: 64 Original Poster	Thanks Have any flash tips Have any tips on using flash in m mode also

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12-25-2008, 04:00 PM	#2
Marc Sabatella Veteran Member Join Date: Sep 2006 Location: Denver, CO Photos: Gallery Posts: 10,685	Av mode doesn't work with manual lenses (unless they have an "A" position on the aperture ring and you use that). Use "M" mode and hit the Green button to get the camera to temporarily stop down, take a meter reading, and set a shutter speed for you. Use DOF preview to view the meter reading live.

12-25-2008, 10:02 PM	#4
Marc Sabatella Veteran Member Join Date: Sep 2006 Location: Denver, CO Photos: Gallery Posts: 10,685	Flash fires full power with manual lenses, you you need to use the old guide number formula: divide the flash guide number by the distance to subject to get the proper aperture, and then set the aperture to that value. It's how they did it in the old days...

12-26-2008, 01:08 AM	#5
denisv Forum Member Join Date: Dec 2008 Location: Slovenia Photos: Gallery Posts: 66	Do any of the auto modes work with preset lenses?

12-26-2008, 02:54 AM	#6
elkarrde Veteran Member Join Date: Oct 2008 Location: Zagreb, Croatia Posts: 387	Originally posted by Barry_S I've using Pentax for 30 years and have a lot of M lens. I received a K20D. Changed setting to permitted aperture lens. Set to AV mode. But the shutter speed read the same, 1/90 at f1.7 or f22. I'm missing something and not sure what. The manual don't tell you much. After messing with it abit, it seems to me that it locks the aperture open and you loss all control. If so how do you adjust the aperture and shutter speed. Thanks yes, when your camera is not in M mode, the lens stays constantly wide-open. switch to M mode, close the aperture, hit the green button - voila! stop-down metering.

12-26-2008, 08:35 AM	#7
Big Dave Veteran Member Join Date: Jan 2008 Location: San Antonio, Texas Photos: Gallery Posts: 547	denisy, Older lenses with auto diapharm work in manual mode, those without auto diapharm will work fine in AV or manual. With smaller M type lenses, you can mount them and then rotate them counter clockwise about ten degrees to allow AV operation. All of the M42 lenses work in AV, because the auto diapharm isn't connected to the camera. They must have a manual/auto switch on the lens set to manual for this, or be locked in manual. By locked in manual, I meanthat the actuator pin must be permenantly depressed. Dave Originally posted by denisv Do any of the auto modes work with preset lenses?

12-26-2008, 08:47 AM	#8
newarts Inactive Account Join Date: Dec 2008 Location: Ames, Iowa, USA Photos: Albums Posts: 2,965	Originally posted by Big Dave denisy, Older lenses with auto diapharm work in manual mode, those without auto diapharm will work fine in AV or manual. With smaller M type lenses, you can mount them and then rotate them counter clockwise about ten degrees to allow AV operation. All of the M42 lenses work in AV, because the auto diaphram isn't connected to the camera. They must have a manual/auto switch on the lens set to manual for this, or be locked in manual. By locked in manual, I mean that the actuator pin must be permenantly depressed. Dave At least with a K100D, the electrical contacts on the camera's flange need to be shorted electrically to insure proper exposure metering and "focus trapping" mode. Some use a piece of aluminum foil to do this; after doing so to prove to myself its necessity, I sanded some paint off the lens' base to make the electrical contact. Dave

12-27-2008, 12:43 AM	#9
George Lama Veteran Member Join Date: Jun 2007 Location: Buffalo/Rochester, NY Photos: Albums Posts: 1,133	With the K10 and my M lenses, since you can't redirect/diffuse the on-body flash as readily, I've had much better results with off-camera flashes, both with an old Focal manual and a new Promaster Digital in Manual mode.