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08-04-2012, 02:31 PM   #1
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MX Depth of field question - problem

HI,
I just got Pentax MX - and I am very happy about my camera. It is pretty selfexplenatory, but even tough I have users manual I can not understand depth of field lever.
Its lever next to lens barrel on the right side of camera and if I push it towards the barrel I should see change - according to users manual. But I do not. Do I miss something, or what should I see, or is camera broken?
Another thing, I suppose my shutter speed is not correct anymore - is there effective guide how to clean - oil the sutters and/or fix it?
Thank you in advance.

08-04-2012, 02:34 PM   #2
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QuoteOriginally posted by em-tx Quote
Its lever next to lens barrel on the right side of camera and if I push it towards the barrel I should see change - according to users manual. But I do not. Do I miss something, or what should I see, or is camera broken?
So that we are on the same page... lens locked correctly and you set the lens to.... say, about f5.6 or f8 and push the lever and you see nothing happening?

Does the time work?
08-04-2012, 02:48 PM   #3
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The wider the aperture the less of a difference the depth of field leaver will show. I have an MX and have just gone back to it for some film fun. I was never real impressed with the depth of field display as it didn't really show much, but then I might have been missing something. But it is suppose to show what is in focus at the given aperture setting. Hence little change shown when the aperture is large, f1.7 like on the nifty fifty. At smaller apertures the view finder should darken.

As for the shutter speed, the dial on the top is the actual shutter speed, but the display in the view finder may be different. It appears that the display dial shifts a little bit and gets out of alignment, which mine has. It does get a little confusing. Otherwise it is a good camera, just we get spoilt with all this modern tech. Hope this helps. Please excuse where I have used the word display, modern tech again, view finder.
08-04-2012, 03:04 PM   #4
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You described problem well. I have this problem at 3.5. At 5.6 is darkening, higher f more darkening. Does it mean - that darkened places are out of focus - darker means more blur? Eventually higher f number bigger depth of field - so more space should be sharp, there for it is rulling out darkening as meaning for blur. Maybe I just do not understand the concept.

I do not quite understand what you mean by time work? I think my camera have not been used for very, very long time and I have feeling, that actually shutter was behind, but its improving.

I found and more less got over links under. not really related - but I think is good idea to put all analog camera problems at 1 place.

I found this: http://www.pentax-manuals.com/manuals/service/mx_sm.pdf
and getting to read this: http://www.pentax-manuals.com/manuals/service/mx_sm.pdf
https://www.pentaxforums.com/forums/pentax-film-slr-discussion/179401-pentax-...-problems.html

08-04-2012, 03:16 PM   #5
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AussieTrev thanks for info and answer. No problem with terminology.

I have a question. At f16 - pushing DOF lever darkening gets significant. If darkening is representing what is in the blur, than it does not make a sense for me. At f16 DOF is big and more things across the frame should be in focus, there for less blur - less darkening.
08-04-2012, 03:24 PM - 1 Like   #6
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QuoteOriginally posted by em-tx Quote
You described problem well. I have this problem at 3.5. At 5.6 is darkening, higher f more darkening. Does it mean - that darkened places are out of focus - darker means more blur? Eventually higher f number bigger depth of field - so more space should be sharp, there for it is rulling out darkening as meaning for blur. Maybe I just do not understand the concept.

I do not quite understand what you mean by time work? I think my camera have not been used for very, very long time and I have feeling, that actually shutter was behind, but its improving.

I found and more less got over links under. not really related - but I think is good idea to put all analog camera problems at 1 place.
In my experience the DOF preview feature is not very useful with slow lenses, such as most zooms. I appreciate it more when using a lens that can go to f/2 or wider.

Darkness does not correspond to out of focus areas. Blur means blur. It really is designed as a "what you see is what you get" preview: the idea is, when you push the lever, whatever remains out of focus in the preview should also be out of focus in the final picture. The darkness is just a side effect.

I believe "time" was a typo, and should have said "does the timer work."
08-04-2012, 03:29 PM   #7
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Sluggo. Thanks. Makes sense.

Mystery Onion - yes my timer works.
08-04-2012, 05:07 PM   #8
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QuoteOriginally posted by em-tx Quote
Mystery Onion - yes my timer works.
Well it sounds like the lever is not broken... as per the other conversations I found it was obvious anyway.

DOF... don't forget to read the section in the manual about the scale engraved along the focus distances. It will help you calculate what you are looking to try and keep in focus based on the F-stop.

I wish I could help explain the science about DOF... when I describe it to people, they get headaches.

08-04-2012, 05:10 PM   #9
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When you press the button the lens stops down to your setting--i.e., the aperture gets smaller per your setting, hence less light and darker. More is in focus with it stopped down--you have to look to see that--not just look at the change of light. It is doing the right thing, you just aren't used to seeing it. The metering is wide open, the DOF preview stops the lens down so you see what the film will see in terms of focus.
08-05-2012, 10:21 AM   #10
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QuoteOriginally posted by Jacquot Quote
When you press the button the lens stops down to your setting--i.e., the aperture gets smaller per your setting, hence less light and darker. More is in focus with it stopped down--you have to look to see that--not just look at the change of light. It is doing the right thing, you just aren't used to seeing it. The metering is wide open, the DOF preview stops the lens down so you see what the film will see in terms of focus.
Thank you - clear. I understand the optic concept, just did not get it how it function in this (analog) camera. Also seems I need to clean focusing screen and mirror.
08-05-2012, 12:56 PM   #11
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The usefulness of DOF preview escapes many, including my wife.
All she perceives is darkening. One must learn to see beyond that.
I hope I have better luck demonstrating it to my daughter...

Chris
08-05-2012, 01:02 PM   #12
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QuoteOriginally posted by ChrisPlatt Quote
The usefulness of DOF preview escapes many, including my wife.
All she perceives is darkening. One must learn to see beyond that.
I hope I have better luck demonstrating it to my daughter...

Chris
I think in my case it does require cleaning optics. I really tried to look at it, but I could not see. a lot....eventually difference. DOF preview was one of the reason I was buying this camera.
08-05-2012, 02:16 PM   #13
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I am loathe to buy/prefer to avoid using an SLR without DOF preview.
I consider it practically a necessity. Once you clean up that camera
and can see beyond the darkening of the viewfinder you may, too.

Chris
08-05-2012, 02:52 PM - 2 Likes   #14
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I find this thread a bit confusing and I know what is happening so I am going to try and make it a bit clearer.

As you know, the smaller the aperture the greater the depth of field, but also the less light hitting the film. The DoF preview lever on the MX and other analog cameras simply closes the aperture of the lens down. It is identical in impact to using the exposure lever on a Spotmatic or the manual/auto switch on a Takumar M42 lens. Using the lever, therefore, does show depth of field, but also, of course, cuts down the light making it darker to see what is happening. At the smallest aperture, e.g., f/22, it may be so dark as to be utterly useless. At moderate apertures, such as f/8, it can give you a reasonable if dim idea of the impact of that f-stop on the image.

This can be seen most clearly when focusing very close-up to something, e.g., a close-up image of a flower. The leaves in the background maybe a smooth green blur wide-open but start gaining some definition at smaller apertures even if they are still far from being in focus.

I know this was all said elsewhere in the thread, I'm just trying to clarify it a little.

Cheers, Kris.
08-05-2012, 03:06 PM   #15
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I use the MX as my only film camera... The DOF preview works exactly the same as it does on the digital pentaxs... easiest way to explain it, is put a soda can at minimum focus and put a soda can behind it a little to the left or right... Now set aperture at like F4 or F5 or something like that, now without pushing the DOF lever focus on the soda can closest, notice how its in focus and everything behind it is out of focus? Now push the lever and you will notice the can behind it becomes in focus because you can now see the correct DOF. dont pay any attention to the dark areas thats just the lens getting dark because the aperture is closing...
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