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08-31-2010, 11:54 AM   #1
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HELP ! M42 lenses values ?3rd party pentax mount

As a dslr camera newbie I'm about to throw in the towel and go back to my basic point & shoot camera. Tried all the suggested settings but photos underexposed even at f2.8 I really have tried !and it's taking all the fun out it.
So I am looking for some feedback as to whether there is a market for my M42 Pentax screwmount lenses.If so, they are going to their new homes !

Teleconvertor 2+ 1 MC Vivitar

28mm f1.28 + Macro. Praktica

50mm f1.2 Sears (some say it's Mamiya originally ?)

75-135mmZoom Sears ( as noted above) " "

My Pentax camera is an istDL2 with standard 18-55 DA SMC lens, any help would be really appreciated .Thanks ...Pemarp

08-31-2010, 12:00 PM   #2
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note that M42 lenses have a tendancy to under expose by about 1-2 stops, but they can be used very effectively by setting the exposure compensation accordingly.

I suggest what you do is try taking a shot of a uniformly lit road, concrete or asphalt pathway or block wall, at each aperture and look at the histogram. Then move the exposure compensation to the +ve side, until the histogram of the lens setting with the mean exposure, (i.e. the one in the middle of the range between most under exposed to least under exposed) is in the middle of the histogram, and shoot that way.

it only takes a few minutes to figure out the correct compensation for each lens.

Once done, if they are all different, you could go as far as putting a label on each lens with the preferred setting so you don't forget.
08-31-2010, 12:11 PM   #3
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1) Shoot in M mode.

2) Select fixed ISO.

3) Select your desired aperture.

4) Don't know your camera, but use Green button properly set (got one?) to lock in the shutter speed.

5) Start smiling.

You can only shoot in M and Av mode with the M42s, and Av mode constantly underexposes. (On my K-x too. Can't use it at all.) It simply "reads" the scene wrong.

Switch to M, problems solved.
08-31-2010, 12:24 PM   #4
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Thanks, there is no green button on this camera,I tried same shot with all possible apertures and they all came out the same, Does it make any difference if the Aperture ring is on A rather than M (Even though I've already set the "MF" on the camera body ?)Thanks.Pemarp M42

08-31-2010, 12:50 PM   #5
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Sears 1.2? Are you sure you don't mean Sears 1:2?
08-31-2010, 12:53 PM   #6
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QuoteOriginally posted by Pemarp Quote
Thanks, there is no green button on this camera,I tried same shot with all possible apertures and they all came out the same, Does it make any difference if the Aperture ring is on A rather than M (Even though I've already set the "MF" on the camera body ?)Thanks.Pemarp M42
"A" setting means "automatic". If you use this setting with a Pentax M42/K adaptor, the lens will not stop down when you take the picture.

"M" setting means "manual". The lens will stop down immediately at the chosen f-stop. You should use this setting.


In Av mode :

- Focus and compose at wide aperture (it's easier)
- Turn the aperture ring at the f-stop you want
- Take the picture

or

- Select the f-stop you want
- Push the lens switch to "A" to focus and compose
- Push the lens switch to "M" before shooting.

As Lowell pointed : you'll probably have to select exp. compensation.
08-31-2010, 12:55 PM   #7
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While there may be no green button, with K mount lenses or M42 lenses in manual, you can meter manual I believe by pressing the AE-L button, which should stop down the lens and meter then open up again for composition, or by using the depth of field preview switch (if available by over rotating the on . off switch) to activate the metering and adjust shutter speed with the front control dial to match neutral exposure.

Note for K mount lenses, if they have an A position -USE IT because otherwise the lens will not respond to the camera aperture settings. If the lens is ouot of th eA position, the metering above must be used, but only in M mode, IN Av mode the lens will never stop down, but will always shoot wide open.

Note that setting MF on the body has to do with focusing not metering or aperture control. You have 3 opptions with the MF / AF switch.

In Manual mode, or AF-C mode the camera will gebave the same, i.e. the shutter will trip regardless of focus confirmation,. In AF-S mode, the shutter will trip only when focus confirmation is achieved.

Try again taking some shots, and post some examples, but go through it methodically, the camera you have is fine, but the old lens support is not really well explained.

WSame thing with M42 lenses in Av Mode. Yes, exposure is off, but it is off by a set number of stops, once adjusted to get neurtal exposure on a uniformly lit and consistant color surface, it will meter correctly.

I use Av mode with M42 lenses a lot. It works just fine once you figure out the exposure compensation needed
08-31-2010, 01:03 PM   #8
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The aperture switch should be on M. Since there's no green button on your camera, use the AE-L button instead. I don't know the *ist DL2 at all, so there may be a menu setup needed to use the AE-L button in this way.

The procedures for using manual lenses on a Pentax digital camera are well laid out at theatre of noise: Using A Manual Lens On A Pentax Digital SLR. Focus with your widest aperture, set the aperture with the lens ring, press the AE-L button to set the shutter speed for the aperture you've set, then shoot.

Good luck!

08-31-2010, 01:06 PM   #9
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Yes, on closer inspection there is another dot......any info on this would be appreciated.Thanks, Pemarp
08-31-2010, 01:09 PM   #10
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QuoteOriginally posted by Pemarp Quote
Yes, on closer inspection there is another dot......any info on this would be appreciated.Thanks, Pemarp
That means it is an F2 lens, not an F1.2 lens. Not surprising as I'm sure Sears never sold an F1.2 lens. Is the lens M42 or K mount? If it's M42 does it have the Auto/Manual switch? BTW, Sears lenses were made by Ricoh, they are usually the same as the Rikenon version.
08-31-2010, 01:22 PM   #11
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The 50mm lens is manual setting only. However the macro and zoom lenses do have the A or M aperture setting, and both would be 1:2.8, thanks. Also the lenses are the screwthread M42 Pentax mount(I use the original Pentax made adapter)

Last edited by Pemarp; 08-31-2010 at 01:26 PM. Reason: insufficient information
08-31-2010, 03:26 PM   #12
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Actually the 50mm would be Auto only. A M42 lens that does not have the Auto/Manual switch can only be used wide open in AV mode unless you modify the lens to keep the aperture lever pushed in.

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/51749-m42-auto...ification.html
08-31-2010, 03:51 PM   #13
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This is a case where someone needs to read a manual....
08-31-2010, 03:53 PM   #14
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By the way:

A/M switches are confusing by their very nature:

You have to flip it so the A or M is EXPOSED and that you can see it on the lens barrel.

You don't flip it to the DIRECTION of the mode you want to use.
08-31-2010, 05:07 PM   #15
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Does the manual even talk about adapters and using M42 lenses? I'd be very surprised if it did. Give the guy a break here. He's not just trying to use the camera in the accepted way with new digital lenses that are made for this camera. What he's doing takes a bit of practice and if you've never had a DSLR or used an adapter before I would imagine it would take you a bit to get it right.

QuoteOriginally posted by hangu Quote
This is a case where someone needs to read a manual....
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