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08-05-2012, 07:56 PM   #16
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Just to throw in my two cents (and that's about what this is worth because I just bought an MX today <g>). MX came with a Vivitar zoom. I pushed in the DOF preview lever and nothing happened. My first assumption was that the DOF lever was broken. After swapping the Vivitar out for a Pentax M50 f1.7, the DOF lever works as advertised. I'm wondering if the OP has a third-party lens mounted and it doesn't respond to the DOF lever. My advice to them would be "try another lens".

Best to all,
Kevin

08-06-2012, 06:44 AM - 1 Like   #17
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em-tx,

To rule out if the lever is operating or not...

Take the lens off and look. One the inside a metal tab to the left or near the DoF lever should move when you work the lever. This is the gadget that will stop-down the lens/initiate the depth-of-field preview. If the metal tab is working, we can say the MX body is working.

Next is the lens.

On the lens... set it for F22 while the lens is off the camera. On Pentax K-mount lenses off the camera, the lens will default to stop-down or in other words the lens' aperture will respond to the F-stop dial. While off the body and set to f22, you should see the smallest opening available if we are talking a 50mm lens here. Also, note the rear of the lens. A flange of metal and usually protected by a blade of metal sticks out of the of the lens. This is the part that mates to the metal tab of the body to be operated by the shutter mechanism or the DoF preview lever. If you work the little metal tab with your finger, does it quickly operate the lens aperture blades? If yes, then you have a properly working lens. If no, then we have a problem.
08-06-2012, 08:06 AM   #18
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If the finder darkens, then the DOF preview lever is working. However, the MX standard screen is not the best for evaluating DOF, but you can see some difference when you know what you are looking for. Old fashioned, dim groundglass is best for checking DOF, like the original 1957 Pentax had.
I even changed the screen on my Leica R6 to groundglass for that reason.
08-06-2012, 03:23 PM   #19
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QuoteOriginally posted by TomB_tx Quote
If the finder darkens, then the DOF preview lever is working. However, the MX standard screen is not the best for evaluating DOF, but you can see some difference when you know what you are looking for. Old fashioned, dim groundglass is best for checking DOF, like the original 1957 Pentax had.
I even changed the screen on my Leica R6 to groundglass for that reason.
Hi Tom,
thanks for message. I do not quite understand what you mean by changing for the groundglass - but sounds really interesting. Just it inspired me, do you know different - possibly better ones?
Since I am novic to analog, I like to spit screen and to know exactly on what and how I am focusing.
Cheers.

08-06-2012, 03:25 PM   #20
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QuoteOriginally posted by MysteryOnion Quote
em-tx,

To rule out if the lever is operating or not...

Take the lens off and look. One the inside a metal tab to the left or near the DoF lever should move when you work the lever. This is the gadget that will stop-down the lens/initiate the depth-of-field preview. If the metal tab is working, we can say the MX body is working.

Next is the lens.

On the lens... set it for F22 while the lens is off the camera. On Pentax K-mount lenses off the camera, the lens will default to stop-down or in other words the lens' aperture will respond to the F-stop dial. While off the body and set to f22, you should see the smallest opening available if we are talking a 50mm lens here. Also, note the rear of the lens. A flange of metal and usually protected by a blade of metal sticks out of the of the lens. This is the part that mates to the metal tab of the body to be operated by the shutter mechanism or the DoF preview lever. If you work the little metal tab with your finger, does it quickly operate the lens aperture blades? If yes, then you have a properly working lens. If no, then we have a problem.
Thanks. Clear.
08-06-2012, 03:32 PM   #21
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Thanks to all. You are making it not just cleat but explaining lot of aside. MX is my first SLR analog - and of course I have to know how to handle it - most importantly, understand how camera is built and functions. I am not proud of my lenses, even i think big zoom is not so bad, but they was super cheap deal, that its hard to believe that camera and lenses looks barely used and function fully

There is idea from Tom_B tx about the groundglass and focusing screens. Does anybody has experience with different focusing screens, eventually where to get them?
08-06-2012, 03:35 PM   #22
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Focusing on groundglass is more like focusing on a (backlit) piece of paper: you judge the image sharpness as you focus until the area you are most interested in is at its sharpest. I find it best to focus quickly as it sharpens until it begins to get unsharp (too far) then back up and find the midpoint of best sharpness. I like a plain screen without split/microprism as it is less distracting. You can't see unsharpness in the split image area: it looks sharp, but divided when out of focus. Likewise you can't judge the DOF in this area, you have to look on the screen around it.
Screens for the MX haven't been made for years, and are hard to find, but do show up on eBay or KEH at times. The plain groundglass MX screen is Pentax type SE, or the LX equivalent (which will fit the MX) is an SE20. Alternately I would use one with a small microprism spot, like the SA1 or SA3.
08-06-2012, 08:40 PM   #23
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A big part of getting the most out of the DOF preview is simply practice. For example, focus on something fairly close with the lens wide open, then close the aperture a stop at a time and see how things closer and farther than your point of focus become sharper as you stop down and the viewfinder becomes darker.

Play with the lever with various lenses under different conditions and look very carefully at how what you see through the viewfinder changes as you stop down. Of course, as the viewfinder gets darker it becomes more difficult to see what you are getting. Nonetheless, the function provides useful information more often than not.

One small trick I've learned is that under very bright condtions you can hold the camera with the right hand and operate the lever while both supporting the camera and shading your right eye and the eyepiece with your left hand.
Shading your eye will make it easier to see what is happening in the dark viewfinder.

In my view practice is more likely to give you a good start with DOF preview than will replacing the focusing screen. Replace the screen later if you really think you need to. I've been an MX user for 30 years and have found the standard screen satisfactory. (People do have widely varying opinions about focusing screens.)

08-07-2012, 04:50 AM   #24
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QuoteOriginally posted by TomB_tx Quote
Screens for the MX haven't been made for years, and are hard to find, but do show up on eBay or KEH at times. The plain groundglass MX screen is Pentax type SE, or the LX equivalent (which will fit the MX) is an SE20. Alternately I would use one with a small microprism spot, like the SA1 or SA3.
If you put an LX screen in an MX the meter will be out slightly. The error is so slight that you won't see it with print film, but you might see it with transparencies (where the +- 1/2 stop plus -1/3 could make a significant difference). The solution is simply to set the ASA 1/3 stop faster than the film's speed.

K.
08-07-2012, 03:50 PM   #25
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QuoteOriginally posted by womble Quote
If you put an LX screen in an MX the meter will be out slightly. The error is so slight that you won't see it with print film, but you might see it with transparencies (where the +- 1/2 stop plus -1/3 could make a significant difference). The solution is simply to set the ASA 1/3 stop faster than the film's speed.

K.
So in case I use GS 20, I have to push film 1/3 higher. Does this screen have split focus? Cheers.
08-07-2012, 03:58 PM   #26
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QuoteOriginally posted by TomB_tx Quote
Focusing on groundglass is more like focusing on a (backlit) piece of paper: you judge the image sharpness as you focus until the area you are most interested in is at its sharpest. I find it best to focus quickly as it sharpens until it begins to get unsharp (too far) then back up and find the midpoint of best sharpness. I like a plain screen without split/microprism as it is less distracting. You can't see unsharpness in the split image area: it looks sharp, but divided when out of focus. Likewise you can't judge the DOF in this area, you have to look on the screen around it.
Screens for the MX haven't been made for years, and are hard to find, but do show up on eBay or KEH at times. The plain groundglass MX screen is Pentax type SE, or the LX equivalent (which will fit the MX) is an SE20. Alternately I would use one with a small microprism spot, like the SA1 or SA3.
Ok. So you are saying that with clear type, I can exactly see what is in the focus and also DOF. If this is true, is there a version, that would allow it, but also show grid? I found grid as very useful for composistion. Cheers.
08-07-2012, 05:47 PM   #27
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If you can find one, the Pentax type SG screen for the MX was plain groundglass with grid.
08-07-2012, 11:24 PM   #28
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LX screens are becoming harder to find and are usually pricey.
MX screens are near impossible to find now.

Chris
08-08-2012, 02:34 PM   #29
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How big difference in real are MX and LX screens? What is the reason that Womble suggest to push film speed 1/3 faster - whats up there with metering?
08-08-2012, 03:28 PM   #30
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The MX meter is calibrated to read MX screens.
LX screens fit the MX but transmit slightly more light.
Many believe that a brighter image is easier to focus.

Chris
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