A Step-by step guide to using M and A Lenses

Stratman · 03-08-2008, 01:02 PM

My K110D seems to meter pretty well with M lenses too. I wonder if a firmware upgrade could fix this, or if it is a pure hardware issue?

**krs** · 03-08-2008, 01:43 PM

If it does pretty well with the K110D, then I presume the same would be true for the K100D and the K100D Super...

AndrewShirley · 03-08-2008, 02:45 PM

You'll notice a lever on the mount of the lens. Set your lens to F22 and look at the aperture blades... pretty small right? Now press the lever and you'll notice the aperture opens right up. The camera always keeps the lens wide open until the exposure. Otherwise, trying to focus at F22 would be very difficult.

Anyway, in M mode, when you press the green-button or optical preview, the camera releases the lever, which allows the lens to stop down to the selected aperture at which point it can measure the exposure. Once done, the camera pushes the lever and the aperture opens fully again.

I just verified, that it does NOT do this in Av mode.

- Andrew

Lensvision · 03-08-2008, 03:35 PM

Originally posted by Lowell Goudge

I have written the following so many times I don't need to even look at the curves any more.

at F1.4 it under exposes by about 1 stop, by F8 it over exposes by 1 to 1 1/2 stops and seems to max at +2 stops at F11, then drop back to 1 1/2 stops at f22-f32.

I have checked this with lthe following lenses
50mm F1.4
100mm F4 Macro
105 mm f2.8,
135mm f2.5
300mm F4
400mm F5.6
70-210 F3.5 (series 1)
and a new tamron 28-75 F2.8 when using the apature ring.

It seems to be a K10D thing, my *istD meters very consistently on all lenses

Interesting.
I'm currently following an available light photography course and using my prime M lenses a lot, mostly at 2.8 sometimes at 3.5 (and using a tripod).
With using the green button the pictures become much lighter then when I expose a bit faster.
You are right about this being a K10D thing, I've read about it on several forums.
I think I'm gonna play a bit with the apature setting next week at the course, see what happens

**Lowell Goudge** · 03-08-2008, 05:29 PM

Originally posted by Lensvision

Interesting.
I'm currently following an available light photography course and using my prime M lenses a lot, mostly at 2.8 sometimes at 3.5 (and using a tripod).
With using the green button the pictures become much lighter then when I expose a bit faster.
You are right about this being a K10D thing, I've read about it on several forums.
I think I'm gonna play a bit with the apature setting next week at the course, see what happens

If you are going to play, find a nice uniform grey surface, sidewalk, paved or gravel road, block wall, etc. (when I began photography, I would meter off such a surface, and then just leave the exposure set that way as opposed to carrying a grey card)

using the green button to set shutter speed, take a photo (not just look at metering) of the surface at each apature click.
In a photo editor, look at the histogram, and note the grey scale mean value. (using PSP X2 I can actually select the central portion of the image and get the grey scale value for only the selection, not so sure about other programs.)
Plot this vs F stop (remember F stop is on a log scale)

If you have all settings on neutral (for JPEG) or shoot raw, each F stop is 45 in greyscale, from the range 25-230, and the camera should meter normally in the 110-120 range (I think the actual point is 110)

I have checked each of my lenses this way, using both the *istD and K10D, ISD is perfect, K10D is as I described.

This has led me to believe pentax knows there is a problem probably with light reflecting off the focusing screen, and has compensated for it in software. Someone else reported that they put an *istD screen in, and it metered perfectly with K mounts but then screwed up the AE lenses. Although without data it is only anticdotal, it kind of supports my theory about a software fudge.

jeffkrol · 03-08-2008, 07:30 PM

You may be interested in this thread:
Has a lot of good info on the "new" type screens...
The "interesting twist" on metering...: News Discussion Forum: Digital Photography Review

JMS · 03-10-2008, 06:21 AM

Originally posted by krs

Thanks for the reminder - I remember reading that, but forgot about it!

For a prime lens - set it once when you put on the lens, and you are in business. I assume with a zoom lens (is there such thing as a manual zoom lens?) it is a bit more challenging!

I usually just set it to the middle focal length- or leave it off altogether.

**krs** · 03-10-2008, 07:38 PM

Originally posted by KjetilH

4. You have to use the green/AE-L button, but you can use the DOF preview in M-mode and then adjust the shutter speed by looking at the light meter in the viewfinder

Can someone provide a bit more insight as to how you do the above?

I have no problem using the green button to set the shutter speed for the given aperture in M mode, but I am not familiar with the rest of the above...

Stratman · 03-10-2008, 07:41 PM

On the K10D, pull the "on off" switch in the opposite direction of "off" you will see the meter in the viewfinder on the right side if i remember correctly, adjust aperture/shutter until it is dead center, and should be properly exposed. If you are using a lens with the "A" setting on the aperture, and set the camera to "M" mode, the meter shows without having to pull the on off switch.

OniFactor · 03-10-2008, 08:07 PM

Originally posted by Stratman

On the K10D, pull the "on off" switch in the opposite direction of "off" you will see the meter in the viewfinder on the right side if i remember correctly, adjust aperture/shutter until it is dead center, and should be properly exposed. If you are using a lens with the "A" setting on the aperture, and set the camera to "M" mode, the meter shows without having to pull the on off switch.

110d's don't have a meter in DOF preview, huh?

Stratman · 03-10-2008, 09:09 PM

Unfortunately, no, i have tried it with my 110D, and no go. BUT, if you can find a decent handheld light meter, they are very handy. Also, i have found the stop down metering on my K110D much much better than it is on the K10D

**krs** · 03-11-2008, 06:25 AM

Originally posted by Stratman

On the K10D, pull the "on off" switch in the opposite direction of "off" you will see the meter in the viewfinder on the right side if i remember correctly, adjust aperture/shutter until it is dead center, and should be properly exposed. If you are using a lens with the "A" setting on the aperture, and set the camera to "M" mode, the meter shows without having to pull the on off switch.

Yep - that did it - thanks! You have to keep the on/off switch in that position, which is a little awkward. The other option appears to be to take a peak, adjust the aperture or shutter speed, and check again (if you have that sort of time)....

Thanks for the insight!

Stratman · 03-11-2008, 03:45 PM

I learned that on a post somewhere in this forum, so I am just relaying what Mo said, haha, glad to help !!

Geekybiker · 03-11-2008, 04:02 PM

Originally posted by Stratman

Unfortunately, no, i have tried it with my 110D, and no go. BUT, if you can find a decent handheld light meter, they are very handy. Also, i have found the stop down metering on my K110D much much better than it is on the K10D

You could always learn BDE.

It'll get you in the right neighborhood at least.

deudeu · 03-17-2008, 01:45 PM

Okay, i should receive a 50mm M f1.7 shortly so I hope I got this right.

Stick the lens in.
Set the focal length (little questions here, should i set it at 50mm or the 75mm equivalent? and that is not possible with the DA lenses, right? I have been looking for this in the menus with the kit lens on but i can't find it)
Set your camera to Av if you want to shoot wide open or M in which case you use the apeture ring.
You tell you K10D to overexpose a bit if you are under f4 and you tell it to underexpose above f4.
Then, use the green button to have the supposebly appropriate exposure.
Probably bracket the first few shots because they it doesn't seam likely the exposure will be right the first time.
Try to learn by heart how the K10d measures the exposure for each fstop in order to be able to shot properly right away in most situation.

Did I forget anything? It sounds chalenging and fun to me, like switching to a classic car and learning how to work the clutch... Looking forward for this lens to get here!

03-08-2008, 07:30 PM	#21
jeffkrol Veteran Member Join Date: Sep 2006 Location: Wisconsin USA Photos: Gallery Posts: 8,434	Hi Lowell. You may be interested in this thread: Has a lot of good info on the "new" type screens... The "interesting twist" on metering...: News Discussion Forum: Digital Photography Review

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03-08-2008, 01:02 PM	#16
Stratman Veteran Member Join Date: Mar 2007 Location: St Louis, Missouri U S A Photos: Gallery \| Albums Posts: 2,464	My K110D seems to meter pretty well with M lenses too. I wonder if a firmware upgrade could fix this, or if it is a pure hardware issue?

03-08-2008, 01:43 PM	#17
krs Site Supporter Join Date: Aug 2007 Location: St. Louis, MO Photos: Gallery Posts: 395 Original Poster	If it does pretty well with the K110D, then I presume the same would be true for the K100D and the K100D Super...

03-08-2008, 02:45 PM	#18
AndrewShirley Inactive Account Join Date: Mar 2007 Location: Barrie, Ontario, Canada Posts: 421	You'll notice a lever on the mount of the lens. Set your lens to F22 and look at the aperture blades... pretty small right? Now press the lever and you'll notice the aperture opens right up. The camera always keeps the lens wide open until the exposure. Otherwise, trying to focus at F22 would be very difficult. Anyway, in M mode, when you press the green-button or optical preview, the camera releases the lever, which allows the lens to stop down to the selected aperture at which point it can measure the exposure. Once done, the camera pushes the lever and the aperture opens fully again. I just verified, that it does NOT do this in Av mode. - Andrew

03-08-2008, 03:35 PM	#19
Lensvision Junior Member Join Date: Feb 2008 Location: The Netherlands Photos: Gallery Posts: 47	Originally posted by Lowell Goudge I have written the following so many times I don't need to even look at the curves any more. at F1.4 it under exposes by about 1 stop, by F8 it over exposes by 1 to 1 1/2 stops and seems to max at +2 stops at F11, then drop back to 1 1/2 stops at f22-f32. I have checked this with lthe following lenses 50mm F1.4 100mm F4 Macro 105 mm f2.8, 135mm f2.5 300mm F4 400mm F5.6 70-210 F3.5 (series 1) and a new tamron 28-75 F2.8 when using the apature ring. It seems to be a K10D thing, my *istD meters very consistently on all lenses Interesting. I'm currently following an available light photography course and using my prime M lenses a lot, mostly at 2.8 sometimes at 3.5 (and using a tripod). With using the green button the pictures become much lighter then when I expose a bit faster. You are right about this being a K10D thing, I've read about it on several forums. I think I'm gonna play a bit with the apature setting next week at the course, see what happens

03-08-2008, 05:29 PM	#20
Lowell Goudge Site Supporter Join Date: Jan 2007 Location: Toronto Photos: Gallery \| Albums Posts: 17,886	Originally posted by Lensvision Interesting. I'm currently following an available light photography course and using my prime M lenses a lot, mostly at 2.8 sometimes at 3.5 (and using a tripod). With using the green button the pictures become much lighter then when I expose a bit faster. You are right about this being a K10D thing, I've read about it on several forums. I think I'm gonna play a bit with the apature setting next week at the course, see what happens If you are going to play, find a nice uniform grey surface, sidewalk, paved or gravel road, block wall, etc. (when I began photography, I would meter off such a surface, and then just leave the exposure set that way as opposed to carrying a grey card) using the green button to set shutter speed, take a photo (not just look at metering) of the surface at each apature click. In a photo editor, look at the histogram, and note the grey scale mean value. (using PSP X2 I can actually select the central portion of the image and get the grey scale value for only the selection, not so sure about other programs.) Plot this vs F stop (remember F stop is on a log scale) If you have all settings on neutral (for JPEG) or shoot raw, each F stop is 45 in greyscale, from the range 25-230, and the camera should meter normally in the 110-120 range (I think the actual point is 110) I have checked each of my lenses this way, using both the istD and K10D, ISD is perfect, K10D is as I described. This has led me to believe pentax knows there is a problem probably with light reflecting off the focusing screen, and has compensated for it in software. Someone else reported that they put an istD screen in, and it metered perfectly with K mounts but then screwed up the AE lenses. Although without data it is only anticdotal, it kind of supports my theory about a software fudge.

03-10-2008, 06:21 AM	#22
JMS Senior Member Join Date: Oct 2007 Location: Wisconsin Posts: 273	Originally posted by krs Thanks for the reminder - I remember reading that, but forgot about it! For a prime lens - set it once when you put on the lens, and you are in business. I assume with a zoom lens (is there such thing as a manual zoom lens?) it is a bit more challenging! I usually just set it to the middle focal length- or leave it off altogether.

03-10-2008, 07:38 PM	#23
krs Site Supporter Join Date: Aug 2007 Location: St. Louis, MO Photos: Gallery Posts: 395 Original Poster	Originally posted by KjetilH 4. You have to use the green/AE-L button, but you can use the DOF preview in M-mode and then adjust the shutter speed by looking at the light meter in the viewfinder Can someone provide a bit more insight as to how you do the above? I have no problem using the green button to set the shutter speed for the given aperture in M mode, but I am not familiar with the rest of the above...

03-10-2008, 07:41 PM	#24
Stratman Veteran Member Join Date: Mar 2007 Location: St Louis, Missouri U S A Photos: Gallery \| Albums Posts: 2,464	On the K10D, pull the "on off" switch in the opposite direction of "off" you will see the meter in the viewfinder on the right side if i remember correctly, adjust aperture/shutter until it is dead center, and should be properly exposed. If you are using a lens with the "A" setting on the aperture, and set the camera to "M" mode, the meter shows without having to pull the on off switch.

03-10-2008, 08:07 PM	#25
OniFactor Veteran Member Join Date: Nov 2007 Location: Binghamton, NY, USA Posts: 643	Originally posted by Stratman On the K10D, pull the "on off" switch in the opposite direction of "off" you will see the meter in the viewfinder on the right side if i remember correctly, adjust aperture/shutter until it is dead center, and should be properly exposed. If you are using a lens with the "A" setting on the aperture, and set the camera to "M" mode, the meter shows without having to pull the on off switch. 110d's don't have a meter in DOF preview, huh?

03-10-2008, 09:09 PM	#26
Stratman Veteran Member Join Date: Mar 2007 Location: St Louis, Missouri U S A Photos: Gallery \| Albums Posts: 2,464	Unfortunately, no, i have tried it with my 110D, and no go. BUT, if you can find a decent handheld light meter, they are very handy. Also, i have found the stop down metering on my K110D much much better than it is on the K10D

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03-11-2008, 06:25 AM	#27
krs Site Supporter Join Date: Aug 2007 Location: St. Louis, MO Photos: Gallery Posts: 395 Original Poster	Originally posted by Stratman On the K10D, pull the "on off" switch in the opposite direction of "off" you will see the meter in the viewfinder on the right side if i remember correctly, adjust aperture/shutter until it is dead center, and should be properly exposed. If you are using a lens with the "A" setting on the aperture, and set the camera to "M" mode, the meter shows without having to pull the on off switch. Yep - that did it - thanks! You have to keep the on/off switch in that position, which is a little awkward. The other option appears to be to take a peak, adjust the aperture or shutter speed, and check again (if you have that sort of time).... Thanks for the insight!

03-11-2008, 03:45 PM	#28
Stratman Veteran Member Join Date: Mar 2007 Location: St Louis, Missouri U S A Photos: Gallery \| Albums Posts: 2,464	I learned that on a post somewhere in this forum, so I am just relaying what Mo said, haha, glad to help !!

03-11-2008, 04:02 PM	#29
Geekybiker Veteran Member Join Date: Feb 2008 Location: Chicagoland Posts: 337	Originally posted by Stratman Unfortunately, no, i have tried it with my 110D, and no go. BUT, if you can find a decent handheld light meter, they are very handy. Also, i have found the stop down metering on my K110D much much better than it is on the K10D You could always learn BDE. It'll get you in the right neighborhood at least.

03-17-2008, 01:45 PM	#30
deudeu Senior Member Join Date: Feb 2008 Location: Paris Posts: 222	Okay, i should receive a 50mm M f1.7 shortly so I hope I got this right. Stick the lens in. Set the focal length (little questions here, should i set it at 50mm or the 75mm equivalent? and that is not possible with the DA lenses, right? I have been looking for this in the menus with the kit lens on but i can't find it) Set your camera to Av if you want to shoot wide open or M in which case you use the apeture ring. You tell you K10D to overexpose a bit if you are under f4 and you tell it to underexpose above f4. Then, use the green button to have the supposebly appropriate exposure. Probably bracket the first few shots because they it doesn't seam likely the exposure will be right the first time. Try to learn by heart how the K10d measures the exposure for each fstop in order to be able to shot properly right away in most situation. Did I forget anything? It sounds chalenging and fun to me, like switching to a classic car and learning how to work the clutch... Looking forward for this lens to get here!