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10-27-2019, 11:47 PM   #1
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DoF preview adapter for K, M, A era lenses.

Hi, please excuse the baited title/subject.
Does such a thing exist? It seems to me (as someone new to Pentax mounts and lenses) that the aperture lever and actuation is a fairly simple affair on old film bodies and their lenses.

I wondered if there’s an adapter or clever trick/mod people have used to get DoF preview on bodies without it, like ME Super?

Thanks!

10-28-2019, 12:18 AM   #2
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A real point of difference of newer Pentax models like my K-1 is Digital preview. Easily thought of as DoF preview on steroids.
10-28-2019, 01:24 AM   #3
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Optical or digital preview as always using off-on-preview lever. Just checked it. Works fine on K1m2.
10-28-2019, 01:37 AM - 1 Like   #4
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QuoteOriginally posted by Beepaitch Quote
Hi, please excuse the baited title/subject.
Does such a thing exist? It seems to me (as someone new to Pentax mounts and lenses) that the aperture lever and actuation is a fairly simple affair on old film bodies and their lenses.

I wondered if there’s an adapter or clever trick/mod people have used to get DoF preview on bodies without it, like ME Super?

Thanks!
There is an old trick that requires a little sleight-of-hand to use and is rather difficult because you don't want to drop your lens. While set at the desired F-stop, and with eye to the viewfinder, release the mount locking tab and rotate the lens to the right as though you were removing it while keeping it flush to the mount flange. When the aperture coupling lever is clear of the camera's coupling the lens will stop down and, although awkward, the subject can be seen at taking aperture.
I would not recommend this for the heavier, long lenses because you usually would only have one hand on the lens and the other holding the camera. It is the only way I know of to see stopped down on these cameras but hard to do while trying to make any useful evaluation of DOF.
For normal to wide-angle focal lengths DOF tables or the scale on the lens may suffice.

10-28-2019, 01:47 AM   #5
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QuoteOriginally posted by beachboy2 Quote
Optical or digital preview as always using off-on-preview lever. Just checked it. Works fine on K1m2.
I only ever use the digital preview. When you use the optical does it stay stopped down as long as you hold the lever?
10-28-2019, 02:13 AM   #6
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QuoteOriginally posted by GUB Quote
I only ever use the digital preview. When you use the optical does it stay stopped down as long as you hold the lever?


I only use optical preview Yes, the lens stays stopped down for as long as the lever (or dedicated button, on newer bodies) is operated.


With aging eyesight, being able to assess the image detail on the rear screen is no longer practical without auxiliary aid, (loupe etc.), using the viewfinder is how I've always done it and it continues to work for me
10-28-2019, 02:26 AM   #7
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QuoteOriginally posted by kypfer Quote
I only use optical preview Yes, the lens stays stopped down for as long as the lever (or dedicated button, on newer bodies) is operated.


With aging eyesight, being able to assess the image detail on the rear screen is no longer practical without auxiliary aid, (loupe etc.), using the viewfinder is how I've always done it and it continues to work for me
Yes I have ageing eyesight too! But a lcd viewfinder (loupe) does wonders.
10-28-2019, 02:30 AM   #8
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QuoteOriginally posted by From1980 Quote
There is an old trick that requires a little sleight-of-hand to use and is rather difficult because you don't want to drop your lens. While set at the desired F-stop, and with eye to the viewfinder, release the mount locking tab and rotate the lens to the right as though you were removing it while keeping it flush to the mount flange ...
Ah clever! That's the sort of thing I meant.

I really REALLY like the ME Super body, and I'm quite happily living without aperture setting in viewfinder, but was missing DoF preview.

I'll continue to think of a way to do this with with some modification of a mount / adapter / body, but for now the unlock-and-twist will do.
I did wonder if a very short extension tube could be modified with a lever to actuate the aperture linkage from outside. I've never used an extension tube but I understand that I'd loose ability to focus at distance with one right?

10-28-2019, 02:47 AM   #9
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QuoteOriginally posted by GUB Quote
I only ever use the digital preview. When you use the optical does it stay stopped down as long as you hold the lever?
Before digital cameras were invented this was the only way DOF preview worked.

Personally I have never understood digital preview, apart from the fact that no picture is stored on the card, what is the difference between DP and taking a picture ?
10-28-2019, 03:12 AM - 1 Like   #10
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QuoteOriginally posted by Beepaitch Quote
Ah clever! That's the sort of thing I meant.

I really REALLY like the ME Super body, and I'm quite happily living without aperture setting in viewfinder, but was missing DoF preview.

I'll continue to think of a way to do this with with some modification of a mount / adapter / body, but for now the unlock-and-twist will do.
I did wonder if a very short extension tube could be modified with a lever to actuate the aperture linkage from outside. I've never used an extension tube but I understand that I'd loose ability to focus at distance with one right?
Yes, you would. Adding anything between the lens mount and mount flange on the camera limits the ability to reach distant focus. Pentax lenses are calibrated with a mount-to-focal plane distance of 45.46 mm.
10-28-2019, 03:18 AM - 1 Like   #11
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QuoteOriginally posted by pschlute Quote
Before digital cameras were invented this was the only way DOF preview worked.

Personally I have never understood digital preview, apart from the fact that no picture is stored on the card, what is the difference between DP and taking a picture ?
Nothing other than having random test shots scattered through your images. I use it exclusively for exposure. For fun I tend to guess the initial exposure and work my way to the ideal histogram.
10-28-2019, 03:20 AM   #12
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QuoteOriginally posted by From1980 Quote
There is an old trick that requires a little sleight-of-hand to use and is rather difficult because you don't want to drop your lens. While set at the desired F-stop, and with eye to the viewfinder, release the mount locking tab and rotate the lens to the right as though you were removing it while keeping it flush to the mount flange. When the aperture coupling lever is clear of the camera's coupling the lens will stop down and, although awkward, the subject can be seen at taking aperture.
I would not recommend this for the heavier, long lenses because you usually would only have one hand on the lens and the other holding the camera. It is the only way I know of to see stopped down on these cameras but hard to do while trying to make any useful evaluation of DOF.
For normal to wide-angle focal lengths DOF tables or the scale on the lens may suffice.
That is a great trick for using M series lenses in AV mode
10-28-2019, 05:51 AM   #13
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QuoteOriginally posted by GUB Quote
Nothing other than having random test shots scattered through your images. I use it exclusively for exposure. For fun I tend to guess the initial exposure and work my way to the ideal histogram.
I hadnt thought of that use for it, and i guess you are right, if you use it a lot you don't have to go and delete those shots.
10-28-2019, 06:51 AM   #14
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QuoteOriginally posted by From1980 Quote
There is an old trick that requires a little sleight-of-hand to use and is rather difficult because you don't want to drop your lens. While set at the desired F-stop, and with eye to the viewfinder, release the mount locking tab and rotate the lens to the right as though you were removing it while keeping it flush to the mount flange. When the aperture coupling lever is clear of the camera's coupling the lens will stop down and, although awkward, the subject can be seen at taking aperture.
I would not recommend this for the heavier, long lenses because you usually would only have one hand on the lens and the other holding the camera. It is the only way I know of to see stopped down on these cameras but hard to do while trying to make any useful evaluation of DOF.
For normal to wide-angle focal lengths DOF tables or the scale on the lens may suffice.
If we think back to 1980, this trick was well known for the M body users.

The Pentax LX actually had a manual stop-down lever I recall, so you could see through the viewfinder what the image would be like at any aperture. The LX was the world's cleverest film camera I think, with this feature, a removable top to allow use as a waist-level finder, interchangeable focus screens, scores of clever little touches like these.
10-28-2019, 07:16 AM   #15
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There's lever or button for DOF preview depending on the model of your body. The lower tier bodies like the K-70/50/30 use a button. The higher tier bodies such as the K-1/K-3/K-5 use a the DOF position on the power switch. Optical or Digital preview is selected in the settings.

Manual focus bodies with preview function had a dedicated lever or button on the lens mount base.
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