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05-21-2014, 02:10 PM   #1
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Manual lens and TVA setting

I'm trying to make sense so maybe someone can confirm for me.

I recently bought my first DSLR, the K-50. I love the fact it has two roller wheels and being an old manual film SLR guy I like using the Tva setting where I can control both the aperture and shutter speed.

My question is regarding a fully manual lens. I'm looking at the Rokinon 14mm lens which is totally manual.

If I set my camera on Tva and, use the roller wheel make sure the camera and lens aperture are the same, Can I then adjust the shutter speed and count on the ISO setting to adjust and give me proper exposure?

Also, is this the way it works with the older M lenses that have no A (auto) aperture electronics?

Sorry if this is widely discusses. I tried searching but didn't find anything focused on this specific question.

05-21-2014, 02:18 PM   #2
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QuoteOriginally posted by TedW Quote
I'm looking at the Rokinon 14mm lens which is totally manual.
It's not fully manual, it supports all the exposure modes (like A lenses), but you do have to focus manually. So TAv and other modes will work just like with DA lenses.

QuoteOriginally posted by TedW Quote
If I set my camera on Tva and, use the roller wheel make sure the camera and lens aperture are the same, Can I then adjust the shutter speed and count on the ISO setting to adjust and give me proper exposure?
With M lenses, the answer to your question is "No". You will not be able to select the aperture setting using the scroll wheel. This article has the full instructions for metering with M and K lenses:
https://www.pentaxforums.com/forums/54-pentax-lens-articles/110657-how-use-me...k-x-k-7-a.html

Adam
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05-21-2014, 02:39 PM   #3
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That was helpful and I've saved the instructions. Thanks so much.


QuoteOriginally posted by Adam Quote
It's not fully manual, it supports all the exposure modes (like A lenses), but you do have to focus manually. So TAv and other modes will work just like with DA lenses.



With M lenses, the answer to your question is "No". You will not be able to select the aperture setting using the scroll wheel. This article has the full instructions for metering with M and K lenses:
https://www.pentaxforums.com/forums/54-pentax-lens-articles/110657-how-use-me...k-x-k-7-a.html
05-21-2014, 04:54 PM   #4
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QuoteOriginally posted by TedW Quote
That was helpful and I've saved the instructions. Thanks so much.
The confusion is quite alright. The term "manual lens" is not too well-defined. It can mean (variously):
  • A lens with a manual aperture diaphragm (this is the traditional sense of the term)
  • A lens limited to manual focus
  • A lens without the Pentax "A" contacts (lacking support for automated aperture control by the body)
  • Any or all of the above
Conversely, an "auto lens" may mean:
  • A lens supporting automatic aperture actuation (this is the traditional sense of the term)
  • A lens supporting focus automation
  • A lens with the Pentax "A" contacts (supports aperture control by the body)
  • Any or all of the above
Are we confused yet?


Steve

05-21-2014, 08:19 PM   #5
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QuoteOriginally posted by stevebrot Quote
The confusion is quite alright. The term "manual lens" is not too well-defined. It can mean (variously):
  • A lens with a manual aperture diaphragm (this is the traditional sense of the term)
  • A lens limited to manual focus
  • A lens without the Pentax "A" contacts (lacking support for automated aperture control by the body)
  • Any or all of the above
Conversely, an "auto lens" may mean:
  • A lens supporting automatic aperture actuation (this is the traditional sense of the term)
  • A lens supporting focus automation
  • A lens with the Pentax "A" contacts (supports aperture control by the body)
  • Any or all of the above
Are we confused yet?


Steve
Or Auto as Auto Sears may seem to mean nothing at all!
05-21-2014, 10:25 PM - 1 Like   #6
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Steve has pretty well nailed it.

Auto sears is likely M42 lenses with auto aperture, which was an early M42 type of lens that permitted wide open focusing but which stopped down to shoot. These lenses lack the manual auto switch of later M42 lenses and require either a special adaptor that pushies the pin to make the aperture follow the aperture ring setting, or a "fix" which involves blocking the pin, usually with a small (3mm) tube between the lens mount and the internal aperture mechanism, over the activation pin.

What you will find, is that with non A lenses, you can't generally shoot Tav mode. Pentax DSLRs have only one mode for non A lenses and that is Av. And Av mode shoots wide open for non A lenses, although for M42 since you stop down the lens manually you do get a form of Av mode with them.

What I didi discover with the Q which is unique, is you can get Tav mode with lenses because in manual mode, they allow auto ISO, which is not possible on a DSLR, manual means fully manual, but on the Q with manual mode and setting shutter on the Q adaptor and stopping the lens manually, letting the ISO move to correct for exposure gives a Tav mode
05-22-2014, 08:13 AM   #7
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QuoteOriginally posted by ivanvernon Quote
Or Auto as Auto Sears may seem to mean nothing at all!
Auto Sears means "auto" as in the first (traditional) use of the term and it means a great deal to those of us who shoot with M42 bodies.* At one time the word "Auto" on the face of the lens was a huge marketing factor and indicated a lens that would "automatically" stop down at exposure time and reopen "automatically" after the exposure. Lenses lacking the "auto" feature would either stop down for exposure with a manual reset of the diaphragm to open required as a second step (semi-auto) or had preset or fully manual diaphragms. The manual/auto switch found on most M42 lenses with auto apertures allows for the use of these lenses on bodies lacking support for the feature (e.g. K-mount SLRs, Soviet Zenits, and others). Lack of aperture automation is a major pain-in-neck when using adapted M42 lenses and is one of the main reasons to opt for Pentax-K or Pentax-M as a reasonably-priced alternative to the Super Taks.


Steve

* The labeling of Pentax mount lenses as "auto" in not limited to M42. The convention continued into the K-mount era for many third-party lenses and yes, there are even a few "non-auto" Asahi/Pentax lenses in both M42 and K-mount. I must mention that several of the original Takumars were labeled as "Auto", but actually had semi-automated diaphragms.

Last edited by stevebrot; 05-22-2014 at 08:25 AM.
05-22-2014, 01:35 PM   #8
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QuoteOriginally posted by stevebrot Quote
Auto Sears means "auto" as in the first (traditional) use of the term and it means a great deal to those of us who shoot with M42 bodies.* At one time the word "Auto" on the face of the lens was a huge marketing factor and indicated a lens that would "automatically" stop down at exposure time and reopen "automatically" after the exposure. Lenses lacking the "auto" feature would either stop down for exposure with a manual reset of the diaphragm to open required as a second step (semi-auto) or had preset or fully manual diaphragms. The manual/auto switch found on most M42 lenses with auto apertures allows for the use of these lenses on bodies lacking support for the feature (e.g. K-mount SLRs, Soviet Zenits, and others). Lack of aperture automation is a major pain-in-neck when using adapted M42 lenses and is one of the main reasons to opt for Pentax-K or Pentax-M as a reasonably-priced alternative to the Super Taks.


Steve

* The labeling of Pentax mount lenses as "auto" in not limited to M42. The convention continued into the K-mount era for many third-party lenses and yes, there are even a few "non-auto" Asahi/Pentax lenses in both M42 and K-mount. I must mention that several of the original Takumars were labeled as "Auto", but actually had semi-automated diaphragms.
Thanks for this clear definition off Auto as used in the Sears lens lineup. I certainly prefer a lens which is Auto in this sense. It is a bit of a pain to have to meter wide open and then manually stop down the lens before firing a shot--the procedure I must use in my Canon FL 55 mm f 1.2 converted to K mount.

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