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01-31-2014, 03:58 PM   #1
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hmmm... not clear how to "manually" set the focal length??

I've searched all over this site and not found an unambiguous answer to what I hope is a simple question:
  • How do I set the focal length for a "converted" (e.g. Leitax) lens without any electronics?

For example, when I attach such a lens, I see the focal length shown greyed out on the LDC as "F --" -- yet there seems to be no way to edit this field (only the ISO is highlighted in blue).

Suggestions gladly welcome.

Michael

01-31-2014, 03:59 PM   #2
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It will only prompt you for a focal length if you have SR turned on.
01-31-2014, 04:05 PM   #3
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Aperture is selected via the external aperture ring. It won't show up, but it'll shoot fine.
01-31-2014, 04:12 PM   #4
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My bad, I didn't read very close...you mean aperture not focal length.
https://www.pentaxforums.com/forums/58-pentax-beginners-corner-q/110658-using...x-dslrs-f.html

01-31-2014, 04:40 PM   #5
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QuoteOriginally posted by MJSfoto1956 Quote
For example, when I attach such a lens, I see the focal length shown greyed out on the LDC as "F --" --
That is aperture f-stop! The lens does not have any way to tell the camera what f-stop it is, so the camera leaves that blank. Its not the same as focal length.

I think that link manacho2005 provided should give you the answers

I think there is a Menu option to input the focal length. Do not convert or multiply it, just input what it is on the lens, the closest lower number. If you cannot find a menu option (Sorry, I dont have that specific camera you have. On mine its the last option in the first field of options. Bottom of page 4 in the menu.) just enable SR and turn the camera off and back on. Now it should ask you at startup. You can disable the SR after inputting the focal length. Oh, and you should go to the menu and Enable Aperture Ring usage, if you haven't already. That is a crucial step, too.
Btw, you can also try reading the camera's manual, maybe it has info there. If not, I think someone made an "improved" and more in-depth manual that you can buy online.
And there are many threads about how to use manual and adapted lenses on Pentax cameras, you can search for them

Last edited by Na Horuk; 01-31-2014 at 04:51 PM.
01-31-2014, 05:08 PM   #6
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guys, not helpful for my particular situation. I don't have a screw mount lens with a 39mm-K mount converter. Imagine you had some sort of "cheap chinese conversion done to an old manual lens" and it was attached to a modern K-3. The camera first automatically switches to Av mode (which is awesome). Then it displays an "unknown focal length" (i.e. K--) on the LCD. However, nowhere does the system "ask" me to type in the focal length. And because there is no focal length, the SR is greyed out. As such, none of the advise works. Perhaps it works for other Pentax cameras or with the Pentax screw mount adapter, but it does not work with my current situation.

In case you are wondering: the K-3 + old, legacy, non-pentad, no-screwmount, converted lens takes exposures just fine -- my only problem is that I would like to "fool" the system so that I can manually type in a focal length for my current (non- Pentax) legacy lens conversion. Or is this simply not possible? if so, are there any chips that can be purchased?

Michael

Last edited by MJSfoto1956; 01-31-2014 at 05:16 PM.
01-31-2014, 05:14 PM   #7
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The link manacho posted is really what you are looking for. Your lens should behave like an M42 or M lens. So it will require stopdown metering in manual mode if you dont shoot wide open. The F-- means it cant read the aperture (like f/5.6 or f/1.8). The focal length is mainly required for shake reduction.
Edit: when you want shake reduction, just set it to on. Then set the camera off and on again. When the camera cant read the lens data like in this case you will be prompted to input the focal length.
01-31-2014, 05:15 PM   #8
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If SR is enabled, upon turning on the body, you will be queried for the focal length. The camera body will shoot in AV or Manual. The aperture is set via the manual aperture ring on the lens, however the EXIF will record either f2.4 or f0 depending on your body / lens combination. I have a K5 and f2.4 is recorded.

This is just an interesting aside, that I have come across. Because I believe that the Leitax mount shorts the camera body interfaces and it realizes that there is a lens mounted - thus the f2.4. With a M42 lens mounted (i.e., a Tak), there is apparently no shorting across the mount interface and f0 is recorded in the EXIF for aperture.

Here is an additional discussion on some related topics....I have 3 of these 2 - Contax Zeiss (28/f2.8 Distagon and a 85/f2.8 Sonnar) along with a Leica 28/f2.8 Emarit-R
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I just read your last post that was put up while I was typing. The SR can also be automatically disabled if you have a wired shutter release attached. The camera body seeing this just assumes that you are up on a tripod and disables SR (which is what applies to me most of the time).

You can also force entry a focal length by going to the (menu) camera menu #4 - and then select the Input Focus Length selection (second from the bottom) - which takes you to the menu that you get when you start up the camera and queries for the focal length.




Last edited by interested_observer; 01-31-2014 at 05:22 PM.
01-31-2014, 05:16 PM   #9
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You'll need to switch your mode dial to M. and use the green button to meter.
If SR is greyed out, check your drive mode. If any self timer or mirror lock set, SR is not available, therefor no focal length to input.
01-31-2014, 05:22 PM   #10
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Tuern the camera off. Switch to manual. Turn camera back on. The menu for focal length should pop up on restart.
01-31-2014, 05:25 PM   #11
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1. Check drive mode
2. Is the contacts on the camera mount shorted when mounting the lens (they should be)? Paint and alike on the mount on the lens can hinder this.
01-31-2014, 05:25 PM   #12
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You can set the focal length manually in the recording mode menu, page 3, last line [Input Focal Length].
01-31-2014, 05:27 PM   #13
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QuoteOriginally posted by MJSfoto1956 Quote
guys, not helpful for my particular situation. I don't have a screw mount lens with a 39mm-K mount converter. Imagine you had some sort of "cheap chinese conversion done to an old manual lens" and it was attached to a modern K-3. The camera first automatically switches to Av mode (which is awesome). Then it displays an "unknown focal length" (i.e. K--) on the LCD. However, nowhere does the system "ask" me to type in the focal length. And because there is no focal length, the SR is greyed out. As such, none of the advise works. Perhaps it works for other Pentax cameras or with the Pentax screw mount adapter, but it does not work with my current situation.

In case you are wondering: the K-3 + old, legacy, non-pentad, no-screwmount, converted lens takes exposures just fine -- my only problem is that I would like to "fool" the system so that I can manually type in a focal length for my current (non- Pentax) legacy lens conversion. Or is this simply not possible? if so, are there any chips that can be purchased?

Michael
Then it displays an "unknown focal length" (i.e. K--) on the LCD. However, nowhere does the system "ask" me to type in the focal length. - I believe that this occurs if you change lenses - say from a DA lens to your Leitax mount lens with out turning off the camera. In this case you can either:
Cycle power on the body - and the focal length query will come up - if SR is enabled.
Or go to the menus - camera menu #4 and select this which will take you to the entry menu. I have never tried this if I have SR disabled or if I have the wired shutter release attached.
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Actually the greying out of the SR is not a function of not entering a focal length, it is a function of one of the following:
  • SR disabled within the menu lists
  • Wired shutter release attached - making the body think that its on a tripod so it disables the SR automagiclly.

01-31-2014, 05:43 PM   #14
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QuoteOriginally posted by MJSfoto1956 Quote
guys, not helpful for my particular situation.
I dont know what your problem is. The camera doesn't know that if the lens is m42, m39 or just a roll of toilet paper.
The reason we gave you multiple answers is because in your first post you talk about F-- and that is something the camera shows where the aperture is usually displayed, which has nothing to do with focal length. The aperture will remain like that, but you will need to set it on the lens. And then you shoot either in Av (continuous metering, camera will not try to stop down the lens, allows auto-ISO) or in M mode (metering via green button, will try to stop down lens to selected aperture if Aperture ring is enabled in menu).

Now, I also wrote in my post the option for manually inputting the focal length. You press Menu, then go to that specific option and press OK and choose the number. Now the camera will behave as if the lens mounted is that focal length, which allows SR use and will also write that number into exif data. You go to the menu where it says Focal Length and then you press OK or the right cursor and then you choose the number.
If you watch this
, you can see at around 1:06 the bottom option literally says "input focal length". This is what you do to manually input focal length for a lens without those contacts.
01-31-2014, 05:57 PM   #15
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QuoteOriginally posted by Na Horuk Quote
If you watch this video, you can see at around 1:06 the bottom option literally says "input focal length". This is what you do to manually input focal length for a lens without those contacts.
yup. got it. read that. understood that.
But for me (after turning the camera on/off/on/off many times, what I see on panel 3 of the camera controls is the following:
  • Live View
  • Electronic Level
  • Horizon Correction
  • AA Filter Simulator
  • Shake Reduction (grey out, thus not selectable)
  • Input Focal Length (greyed out, thus not selectable)

Any other ideas?

M
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