How do you operate on MANUAL using a lens without the A, on the MF Pentax 645?

**Pepe Guitarra** · 03-23-2017, 08:15 PM

I recently got a Pentax 645 camera (originally designed for Medium Format Pentax-A lenses). I have an adaptar to use the 6x7 to 645 lenses, but the 6x7 lenses do not have an A, they are 6x7 Bayonet Takumars. The 645 manual explains how to use the 645 in manual mode when an A lens is on the camera. Does anyone know how to use the camera on manual mode with a lens without the A? I know that the DSLRs have a green button to stop down, but how is it done with the 645? I appreciate your response. Thanks, Pepe.

Adam · 03-23-2017, 08:35 PM

You don't need to stop down meter. The adapter has the aperture coupler, so just select the desired aperture on the aperture ring and fire away with the camera in Av mode. Or, in M mode, follow the meter reading that you see in the viewfinder.

**Pepe Guitarra** · 03-23-2017, 09:05 PM

Thanks Adam, I will try it.

**Pepe Guitarra** · 03-24-2017, 02:13 PM

I shot one roll of 120 film with the 645 and got good results. The camera sets the shutter speed, but I cannot know it, so I have to use some of my Sunny 16 rule to determine the proper aperture that would set a correct exposure. I guess, if I were using a Pentax-A lens, I could see the shutter speed on the viewfinder. Am I correct here? Here are some of the shots ( I developed on Ilfotec DDX (1:9) for 16min at 68F.

---------- Post added 03-24-17 at 02:34 PM ----------

**boriscleto** · 03-24-2017, 02:53 PM

You should be able to use M mode as well as Av if the lens doesn't have an A setting...

**Pepe Guitarra** · 03-24-2017, 03:22 PM

Originally posted by boriscleto

You should be able to use M mode as well as Av if the lens doesn't have an A setting...

Can you see the aperture and the shutter speed ON THE SCREEN of the viewfinder when focussing? I did not see it.

----------------

EDIT: Never mind the above, I was able to find the manual on line and found out how to set speed/aperture/exposure. THanks, Pepe

03-23-2017, 08:15 PM	#1
Pepe Guitarra Site Supporter Join Date: Nov 2010 Location: California Photos: Gallery \| Albums Posts: 2,223	How do you operate on MANUAL using a lens without the A, on the MF Pentax 645? I recently got a Pentax 645 camera (originally designed for Medium Format Pentax-A lenses). I have an adaptar to use the 6x7 to 645 lenses, but the 6x7 lenses do not have an A, they are 6x7 Bayonet Takumars. The 645 manual explains how to use the 645 in manual mode when an A lens is on the camera. Does anyone know how to use the camera on manual mode with a lens without the A? I know that the DSLRs have a green button to stop down, but how is it done with the 645? I appreciate your response. Thanks, Pepe.

03-23-2017, 08:35 PM	#2
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,595	You don't need to stop down meter. The adapter has the aperture coupler, so just select the desired aperture on the aperture ring and fire away with the camera in Av mode. Or, in M mode, follow the meter reading that you see in the viewfinder. Adam PentaxForums.com Webmaster (Site Usage Guide \| Site Help \| My Photography) PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

03-24-2017, 02:13 PM	#4
Pepe Guitarra Site Supporter Join Date: Nov 2010 Location: California Photos: Gallery \| Albums Posts: 2,223 Original Poster	I tried it on a Neopan 100 Acros 120 film and got good results I shot one roll of 120 film with the 645 and got good results. The camera sets the shutter speed, but I cannot know it, so I have to use some of my Sunny 16 rule to determine the proper aperture that would set a correct exposure. I guess, if I were using a Pentax-A lens, I could see the shutter speed on the viewfinder. Am I correct here? Here are some of the shots ( I developed on Ilfotec DDX (1:9) for 16min at 68F. ---------- Post added 03-24-17 at 02:34 PM ----------

03-24-2017, 03:22 PM	#6
Pepe Guitarra Site Supporter Join Date: Nov 2010 Location: California Photos: Gallery \| Albums Posts: 2,223 Original Poster	Originally posted by boriscleto You should be able to use M mode as well as Av if the lens doesn't have an A setting... Can you see the aperture and the shutter speed ON THE SCREEN of the viewfinder when focussing? I did not see it. ---------------- EDIT: Never mind the above, I was able to find the manual on line and found out how to set speed/aperture/exposure. THanks, Pepe Last edited by Pepe Guitarra; 03-24-2017 at 05:20 PM.

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03-23-2017, 09:05 PM	#3
Pepe Guitarra Site Supporter Join Date: Nov 2010 Location: California Photos: Gallery \| Albums Posts: 2,223 Original Poster	Thanks Adam, I will try it.

03-24-2017, 02:53 PM	#5
boriscleto Loyal Site Supporter Join Date: Dec 2009 Location: North Syracuse, NY Photos: Gallery Posts: 16,475	You should be able to use M mode as well as Av if the lens doesn't have an A setting...