[jpzk]

I should have posted this thread in a "beginner's" one !

I bought this lens quite a while back, thinking I would use it fairly regularly but I have yet to really put it to the test.
I've reviewed the lens "review" on PF, looking for some more info but what I am confused about is:
Here is the review section-thread: https://www.pentaxforums.com/userreviews/vivitar-135mm-f-2-8-1-2-close-focusing.html

Can this lens be used for the entire aperture spectrum - from F2.8 to F22 or is this a lens that will only shoot wide open?

Since the F-stop is not seen on the camera display -- only the F - - - is showing, as expected, will I get F5.6 if I turn the aperture ring to F5.6, or will it only shoot at the widest aperture all the time ?

I read this thread:
https://www.pentaxforums.com/forums/pentax-beginners-corner-q/110658-using-ma...x-dslrs-f.html
Would that be the same procedure as for my Vivitar Close Focusing lens?

Thanks for any feedback.

JP

---

Last edited by jpzk; 12-09-2012 at 05:17 PM.

[stevebrot]

You should be able to shoot at the aperture of your choice. Did you buy the M42 or a K-mount version?

• M42 (adapted), you have to manually stop the lens down to meter and also at exposure time. Use the A/M slider at the base of the lens. Use M-mode with green button metering.
• K-mount (non-A contact) use M-mode and green button metering. Be sure you are configured to allow the aperture ring.
• K-mount (A contact) All exposure modes should work with the aperture ring in the A position.

Steve

[jpzk]

Did you buy the M42 or a K-mount version?

• M42 (adapted), you have to manually stop the lens down to meter and also at exposure time. Use the A/M slider at the base of the lens.
• K-mount (non-A contact) use M-mode and green button metering. Be sure you are configured to allow the aperture ring.
• K-mount (A contact) All exposure modes should work with the aperture ring in the A position.

Steve

Thanks Steve.

It is a K-mount, without the "A" contact.

So, OK, I would use the M mode plus Green Button metering, as you explain.
Yes, the camera is already set for allowing aperture ring and of course, I enter the focal length when turning the camera ON.

So, I assume that I have to follow the steps in the aforementioned thread : https://www.pentaxforums.com/forums/pentax-beginners-corner-q/110658-using-ma...x-dslrs-f.html ?

I am never too sure about the missing aperture info on the camera display; that lead me to believe (erroneously) that it always shot wide open.
I don't think it (aperture) would show in the EXIF data either .. right?

Cheers.

JP

[msatlas]

Without the A contacts, the camera doesn't know what aperture you're using. But it does still stop down the aperture when you take a picture. That's also why DOF preview works even without A contacts.

A lot of old film cameras don't display the aperture in the viewfinder either. I find this somewhat annoying, but it's easy enough to count the clicks from wide open to figure out what f-stop you're using.

[jpzk]

Without the A contacts, the camera doesn't know what aperture you're using. But it does still stop down the aperture when you take a picture. That's also why DOF preview works even without A contacts.

A lot of old film cameras don't display the aperture in the viewfinder either. I find this somewhat annoying, but it's easy enough to count the clicks from wide open to figure out what f-stop you're using.

Thanks for the info.

I don't quite get this bit about using the DOF preview to meter, but that's quite alright.
As long as I know that whatever aperture has been chosen (on the aperture ring) is the one I wanted, that's all fine with me.

Cheers.

JP

[msatlas]

Let me see if I can explain it for you. Assume for both of these examples, you're using aperture priority.

If you use a lens with A contacts, the camera knows two pieces of information: the maximum aperture of the lens, and the aperture you're planning to use. So for an f/2.8 lens, the camera takes a light meter reading with the lens wide open. If the light dictates a 1/100 shutter speed, the camera can then decide the actual shutter speed to use depending on what aperture you want to use. So if you set it to f/4, the camera can decide to go to 1/50 shutter to match the 1 stop slower aperture.

Without A contacts, the camera doesn't know anything about the aperture of the lens. Not the maximum aperture, and not what aperture you're planning to use. So taking a meter reading at maximum aperture doesn't work. So when you activate DOF preview when the camera doesn't know the aperture of the lens, the camera stops down the lens, and takes a meter reading of the actual light coming through the lens as will happen when you take the picture. The camera then sets a shutter speed based on this light measurement.

[jpzk]

Without A contacts, the camera doesn't know anything about the aperture of the lens. Not the maximum aperture, and not what aperture you're planning to use. So taking a meter reading at maximum aperture doesn't work. So when you activate DOF preview when the camera doesn't know the aperture of the lens, the camera stops down the lens, and takes a meter reading of the actual light coming through the lens as will happen when you take the picture. The camera then sets a shutter speed based on this light measurement.

Thanks a bunch !! You know what? It now makes sense !

One last "beginner's" question if you don't mind: I assume that you would activate the "optical" preview vs. the "digital" version ?

JP

[msatlas]

Yeah, you need the optical preview. On the K-5, it's the iris icon on the power switch. Just flick it past ON and you'll activate DOF preview.



Stop-down metering works best in M mode. But when you hit DOF preview the camera will set the shutter speed for you so it's not completely manual.

[jpzk]

Yeah, you need the optical preview. On the K-5, it's the iris icon on the power switch. Just flick it past ON and you'll activate DOF preview.



Stop-down metering works best in M mode. But when you hit DOF preview the camera will set the shutter speed for you so it's not completely manual.

Very good !!
Thanks a whole bunch for the info !

JP