Takumar Question // Exposure & Aperture

BBear · 12-03-2008, 09:52 PM

Just received a Super Takumar 135 f/2.5

Two questions after some playing time:

1) does it matter how I set the aperture ring? I mean, it only seems to change the aperture if I leave it in AUTO (MAN. appearing).

2) Interestingly, exposure seems to be good for any aperture BUT f/2.5! It is absolutely underexposing...

I dont have pictures to show, but I can provide shutter values for comparison:

SPOT Metering:
f/2.5 > it gives me 1/180 (totally dark)
f/4.0 > it gives me 1/6

(right exposure)

MATRIX Metering
f/2.5 > 1/60
f/4.0 > 1/10

Weird weird weird..... Any ideas?

hahifuheho · 12-03-2008, 11:39 PM

From my short experience with a 50 1.4 Super Tak, "MAN" appearing means the lens will work in manual mode (for aperture).

As for exposure I cannot say anything yet since I still do not have that M42 to K-mount adapter from ebay.

stevebrot · 12-03-2008, 11:40 PM

Originally posted by BBear

Just received a Super Takumar 135 f/2.5

Two questions after some playing time:

1) does it matter how I set the aperture ring? I mean, it only seems to change the aperture if I leave it in AUTO (MAN. appearing).

2) Interestingly, exposure seems to be good for any aperture BUT f/2.5! It is absolutely underexposing...

I dont have pictures to show, but I can provide shutter values for comparison:

SPOT Metering:
f/2.5 > it gives me 1/180 (totally dark)
f/4.0 > it gives me 1/6

(right exposure)

MATRIX Metering
f/2.5 > 1/60
f/4.0 > 1/10

Weird weird weird..... Any ideas?

If "Man" is visible, than the switch is in the manual position. That is where it should be unless you are using a m-42 body.

As for the metering issues...Welcome to the wonderful world of manual metering on the K10D. The owner's manual indicates that metering is unreliable using non-A mount lenses and it is not kidding. For the most part there is significant underexposure at wider apertures (wider than f/4). Some lenses also have over/underexposure at the narrow end as well. My Jupiter-9, for example will underexpose a full 2-3 stops at f/2, but is fine at f/4-f/16. The cause is poorly understood and has been the topic of a ton of discussion. It seems to be related to how the meter voltages are processed and/or certain dynamics of the focus screen.

Here is the drill for your Tak:

Shoot in AV mode with the lens set to manual aperture
Forget about matrix metering. The camera will default to center-weighted with non-A lenses. (Spot still works though)
Focus wide open and stop down to the desired aperture.
Take a shot and chimp the histogram
If needed, adjust the exposure compensation to shift the curve and try again

Enjoy!

Steve

(Has far too much experience with this matter...see sig...)

sharko · 12-03-2008, 11:43 PM

I just got a Super Takumar 55mm f/1.8 and it seems underexposes a bit wide open but setting a +.05 on the exposure takes care of it since they work best in AV mode. My other takumar, the SMC 135mm f/3.5 seems to expose right at all apertures so I'm not sure what it could be...I do have a katz eye in my k10d but that shouldn't affect anything but spot metering.

stevebrot · 12-03-2008, 11:58 PM

Originally posted by sharko

I just got a Super Takumar 55mm f/1.8 and it seems underexposes a bit wide open but setting a +.05 on the exposure takes care of it since they work best in AV mode. My other takumar, the SMC 135mm f/3.5 seems to expose right at all apertures so I'm not sure what it could be...I do have a katz eye in my k10d but that shouldn't affect anything but spot metering.

There are some reports that the Katzeye screen provides a partial cure. Since you are only seeing a half stop bias wide open, I am tempted to believe that the claims are true. My Rikenon 50/1.7 requires +1.5 exposure compensation wide open. Ditto for my Pentax-M 50/1.7.

Steve

BTW...Lowell Goudge swears that the older *istD screens also provide a cure.

Jewelltrail · 12-04-2008, 12:23 AM

What stevebrot says is all good and better said than I can do. All I'll add is stick with it and you will get better. I have empathy for you because I remember my early attempts at metering lenses before the As and I sure did get frustrated.

You can also use the "Sunny f/16 Anchor Point." There is a great explanation of it and how to use only your brain to expose correctly here Ultimate Exposure Computer

Best of luck to you!

dlacouture · 12-04-2008, 02:17 AM

Well, this problem is linked to the focus screen...

The standard focus screen is not made to be used with m42 lenses, but with PK-A lenses where the metering is always done wide open and the aperture is controlled from the body.

Switching to a LL60 screen does solve the problem (altough it imposes a constant 1/3Ev comp).

At least, I don't have metering problems anymore with my three m42 lenses and my PK-M f/1.2 lens...

The whole story : k10 split-screen, lf80 & ll60 exposure accuracy

christinelandon · 12-04-2008, 04:18 AM

Another fine thread. Thanks to BBear, Stevebrot, and all who contributed. This is the sort of considerate, mutual support that gives this site its useful and welcome character...

BBear · 12-04-2008, 07:46 AM

Originally posted by stevebrot

If "Man" is visible, than the switch is in the manual position.

Thanks for the clarification!

Originally posted by stevebrot

As for the metering issues...Welcome to the wonderful world of manual metering on the K10D. The owner's manual indicates that metering is unreliable using non-A mount lenses and it is not kidding.

Yeah... right on! They do know their products!

(Un)fortunately, it seems like I only have the underexposure when wide-open, stopped down it seems to be fine!

BBear · 12-04-2008, 07:47 AM

Originally posted by dlacouture

Well, this problem is linked to the focus screen...

hmm... in my particular case, I do have the ebay focus screen... just for the record!

**Lowell Goudge** · 12-04-2008, 08:05 AM

Originally posted by stevebrot

There are some reports that the Katzeye screen provides a partial cure. Since you are only seeing a half stop bias wide open, I am tempted to believe that the claims are true. My Rikenon 50/1.7 requires +1.5 exposure compensation wide open. Ditto for my Pentax-M 50/1.7.

Steve

BTW...Lowell Goudge swears that the older *istD screens also provide a cure.

Steve

Thanks for the reference, but I will swear to nothing, I will however repeat my observation with data.

Just to clarify, I have attached a link to the graph I posted showing the K10D and *istD (each with their factory screen) metering using a K 50mm F1.4,

There is an additional line showing the K10D metering using the *istD screen.

What this shows is that I can replicate the *istD metering on a K10D by using the *istD screen.

https://www.pentaxforums.com/forums/241716-post69.html

Note, I believe my copy (perhaps all) of the K50mm F1.4 have a slight error in apature setting as you stop down. This is shown by the slightly increasing grey scale value on the chart.

For the OP, welcome to the wonderful wacky world of K10D metering

dlacouture · 12-04-2008, 08:54 AM

BBear, I've tried the chinese split-screen, and it behaves exactly like the original screen, meaning that you'll have underexposure between f/1.2 and f/4, then f/4-5.6 seems ok, then F/5.6 and above suffer from overexposure.

12-03-2008, 09:52 PM	#1
BBear Veteran Member Join Date: Mar 2008 Location: CT / NY Photos: Gallery Posts: 822	Takumar Question // Exposure & Aperture Just received a Super Takumar 135 f/2.5 Two questions after some playing time: 1) does it matter how I set the aperture ring? I mean, it only seems to change the aperture if I leave it in AUTO (MAN. appearing). 2) Interestingly, exposure seems to be good for any aperture BUT f/2.5! It is absolutely underexposing... I dont have pictures to show, but I can provide shutter values for comparison: SPOT Metering: f/2.5 > it gives me 1/180 (totally dark) f/4.0 > it gives me 1/6 (right exposure) MATRIX Metering f/2.5 > 1/60 f/4.0 > 1/10 Weird weird weird..... Any ideas?

12-03-2008, 11:40 PM	#3
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by BBear Just received a Super Takumar 135 f/2.5 Two questions after some playing time: 1) does it matter how I set the aperture ring? I mean, it only seems to change the aperture if I leave it in AUTO (MAN. appearing). 2) Interestingly, exposure seems to be good for any aperture BUT f/2.5! It is absolutely underexposing... I dont have pictures to show, but I can provide shutter values for comparison: SPOT Metering: f/2.5 > it gives me 1/180 (totally dark) f/4.0 > it gives me 1/6 (right exposure) MATRIX Metering f/2.5 > 1/60 f/4.0 > 1/10 Weird weird weird..... Any ideas? If "Man" is visible, than the switch is in the manual position. That is where it should be unless you are using a m-42 body. As for the metering issues...Welcome to the wonderful world of manual metering on the K10D. The owner's manual indicates that metering is unreliable using non-A mount lenses and it is not kidding. For the most part there is significant underexposure at wider apertures (wider than f/4). Some lenses also have over/underexposure at the narrow end as well. My Jupiter-9, for example will underexpose a full 2-3 stops at f/2, but is fine at f/4-f/16. The cause is poorly understood and has been the topic of a ton of discussion. It seems to be related to how the meter voltages are processed and/or certain dynamics of the focus screen. Here is the drill for your Tak: Shoot in AV mode with the lens set to manual aperture Forget about matrix metering. The camera will default to center-weighted with non-A lenses. (Spot still works though) Focus wide open and stop down to the desired aperture. Take a shot and chimp the histogram If needed, adjust the exposure compensation to shift the curve and try again Enjoy! Steve (Has far too much experience with this matter...see sig...) Last edited by stevebrot; 12-04-2008 at 12:04 AM.

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12-03-2008, 11:39 PM	#2
hahifuheho Forum Member Join Date: Sep 2008 Location: Monterrey, Mexico Posts: 71	From my short experience with a 50 1.4 Super Tak, "MAN" appearing means the lens will work in manual mode (for aperture). As for exposure I cannot say anything yet since I still do not have that M42 to K-mount adapter from ebay.

12-03-2008, 11:43 PM	#4
sharko Senior Member Join Date: May 2008 Location: City of Angels Photos: Gallery Posts: 278	I just got a Super Takumar 55mm f/1.8 and it seems underexposes a bit wide open but setting a +.05 on the exposure takes care of it since they work best in AV mode. My other takumar, the SMC 135mm f/3.5 seems to expose right at all apertures so I'm not sure what it could be...I do have a katz eye in my k10d but that shouldn't affect anything but spot metering.

12-03-2008, 11:58 PM	#5
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by sharko I just got a Super Takumar 55mm f/1.8 and it seems underexposes a bit wide open but setting a +.05 on the exposure takes care of it since they work best in AV mode. My other takumar, the SMC 135mm f/3.5 seems to expose right at all apertures so I'm not sure what it could be...I do have a katz eye in my k10d but that shouldn't affect anything but spot metering. There are some reports that the Katzeye screen provides a partial cure. Since you are only seeing a half stop bias wide open, I am tempted to believe that the claims are true. My Rikenon 50/1.7 requires +1.5 exposure compensation wide open. Ditto for my Pentax-M 50/1.7. Steve BTW...Lowell Goudge swears that the older *istD screens also provide a cure.

12-04-2008, 12:23 AM	#6
Jewelltrail Veteran Member Join Date: May 2008 Location: Rhode Island Photos: Albums Posts: 4,180	What stevebrot says is all good and better said than I can do. All I'll add is stick with it and you will get better. I have empathy for you because I remember my early attempts at metering lenses before the As and I sure did get frustrated. You can also use the "Sunny f/16 Anchor Point." There is a great explanation of it and how to use only your brain to expose correctly here Ultimate Exposure Computer Best of luck to you!

12-04-2008, 02:17 AM	#7
dlacouture Veteran Member Join Date: Jul 2008 Location: Var, South of France Photos: Albums Posts: 1,074	Well, this problem is linked to the focus screen... The standard focus screen is not made to be used with m42 lenses, but with PK-A lenses where the metering is always done wide open and the aperture is controlled from the body. Switching to a LL60 screen does solve the problem (altough it imposes a constant 1/3Ev comp). At least, I don't have metering problems anymore with my three m42 lenses and my PK-M f/1.2 lens... The whole story : k10 split-screen, lf80 & ll60 exposure accuracy

12-04-2008, 04:18 AM	#8
christinelandon Veteran Member Join Date: Jan 2008 Location: Seattle, Washington, USA Photos: Gallery Posts: 812	Another fine thread. Thanks to BBear, Stevebrot, and all who contributed. This is the sort of considerate, mutual support that gives this site its useful and welcome character...

12-04-2008, 07:46 AM	#9
BBear Veteran Member Join Date: Mar 2008 Location: CT / NY Photos: Gallery Posts: 822 Original Poster	Originally posted by stevebrot If "Man" is visible, than the switch is in the manual position. Thanks for the clarification! Originally posted by stevebrot As for the metering issues...Welcome to the wonderful world of manual metering on the K10D. The owner's manual indicates that metering is unreliable using non-A mount lenses and it is not kidding. Yeah... right on! They do know their products! (Un)fortunately, it seems like I only have the underexposure when wide-open, stopped down it seems to be fine!

12-04-2008, 07:47 AM	#10
BBear Veteran Member Join Date: Mar 2008 Location: CT / NY Photos: Gallery Posts: 822 Original Poster	Originally posted by dlacouture Well, this problem is linked to the focus screen... hmm... in my particular case, I do have the ebay focus screen... just for the record!

12-04-2008, 08:05 AM	#11
Lowell Goudge Site Supporter Join Date: Jan 2007 Location: Toronto Photos: Gallery \| Albums Posts: 17,887	Originally posted by stevebrot There are some reports that the Katzeye screen provides a partial cure. Since you are only seeing a half stop bias wide open, I am tempted to believe that the claims are true. My Rikenon 50/1.7 requires +1.5 exposure compensation wide open. Ditto for my Pentax-M 50/1.7. Steve BTW...Lowell Goudge swears that the older istD screens also provide a cure. Steve Thanks for the reference, but I will swear to nothing, I will however repeat my observation with data. Just to clarify, I have attached a link to the graph I posted showing the K10D and istD (each with their factory screen) metering using a K 50mm F1.4, There is an additional line showing the K10D metering using the istD screen. What this shows is that I can replicate the istD metering on a K10D by using the *istD screen. https://www.pentaxforums.com/forums/241716-post69.html Note, I believe my copy (perhaps all) of the K50mm F1.4 have a slight error in apature setting as you stop down. This is shown by the slightly increasing grey scale value on the chart. For the OP, welcome to the wonderful wacky world of K10D metering

12-04-2008, 08:54 AM	#12
dlacouture Veteran Member Join Date: Jul 2008 Location: Var, South of France Photos: Albums Posts: 1,074	BBear, I've tried the chinese split-screen, and it behaves exactly like the original screen, meaning that you'll have underexposure between f/1.2 and f/4, then f/4-5.6 seems ok, then F/5.6 and above suffer from overexposure.