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03-16-2017, 09:48 AM   #1
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Pentax MX shutter speed dial

Yet another beginner question from me about analog photography.
So I've been out shooting my very first roll of film with my "new" Pentax MX. All was well, it was a very pleasant experience, I fell in love with this tiny little piece of photographic history. At one time I was trying to use a given aperture and so I adjusted the shutter speed accordingly. However the optimal speed for that aperture was between 1/1000 and 1/500... so while looking through the viewfinder, I found that the green LED lit up while I left the shutter speed dial between the 500 and 1000 settings. Only one frame was shot this way, but I've been wondering if doing so actually works well and sets an actual speed between the two settings, or I may have messed up the shot and could damage the camera's mechanism. This camera being an analog device, I suspected that I could get away with it, unlike with a digital device.

I'm in great anticipation about my first roll, I hope the light seals are well and I didn't waste a whole roll of film.

03-16-2017, 10:08 AM - 1 Like   #2
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QuoteOriginally posted by gtxSeries Quote
I found that the green LED lit up while I left the shutter speed dial between the 500 and 1000 settings. Only one frame was shot this way, but I've been wondering if doing so actually works well and sets an actual speed between the two settings, or I may have messed up the shot and could damage the camera's mechanism.
The shutter in your MX is fully mechanical and does not support stepless speeds. Although I don't know if it will damage the shutter,* I would avoid shooting with the shutter dial between steps.


Steve

* With some shutters damage would be a sure thing for that case. The actual behavior (next lower speed, x-sync speed, or travel with no opening) of the MX shutter is hard to say without detailed knowledge of the mechanism.

Last edited by stevebrot; 03-16-2017 at 11:57 AM.
03-16-2017, 10:23 AM   #3
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QuoteOriginally posted by gtxSeries Quote
Yet another beginner question from me about analog photography.
So I've been out shooting my very first roll of film with my "new" Pentax MX. All was well, it was a very pleasant experience, I fell in love with this tiny little piece of photographic history. At one time I was trying to use a given aperture and so I adjusted the shutter speed accordingly. However the optimal speed for that aperture was between 1/1000 and 1/500... so while looking through the viewfinder, I found that the green LED lit up while I left the shutter speed dial between the 500 and 1000 settings. Only one frame was shot this way, but I've been wondering if doing so actually works well and sets an actual speed between the two settings, or I may have messed up the shot and could damage the camera's mechanism. This camera being an analog device, I suspected that I could get away with it, unlike with a digital device.

I'm in great anticipation about my first roll, I hope the light seals are well and I didn't waste a whole roll of film.
You might be right and it *might* be OK and do what you think it will. You can also often center the LED "needle" by changing the aperture 1/2 stop, though the availability of a 1/2 EV click-stop for that particular aperture setting would depend on the specific aperture and lens.

On the other hand, that fraction of a stop shouldn't be all that significant with negative film. If you're shooting slide film and you truly want more precision, possibly the MX isn't the very best choice.
03-16-2017, 11:10 AM   #4
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Thanks!

I've been shooting a roll of Kodak Gold 200. I don't know how permissive film is, yet... so I've been just trying to be as precise as possible.

03-16-2017, 02:26 PM - 1 Like   #5
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Interesting question. I'd go with the others and say that half a stop difference shouldn't make too much difference on negative film, especially if you choose to overexpose. Depending on the lens and distance you focused on, half a stop of an aperture probably shouldn't really make a noticeable difference, either.

I was especially worried about dialing an "intermediate" shutter speed on my older cameras (as in folders with compur shutters and such) which don't have any hard stops on their shutter dials until I finally got one that came with a manual. It explicitly says that it's totally fine to set the dial anywhere and it will gradually change the shutter speed accordingly, as it's all connected to one spring, except for the fastest speed that engages an additional "booster" spring on that model. To use that speed, it should be made sure to never set the dial between that fastest speed and the second one.
No idea how and if that translates to the MX or other comparable cameras. If each shutter speed on a more advanced mechanical camera is connected to its own spring, I guess it should be avoided. Maybe someone who took the time to look at an exploded view of the MX or even took one apart could shed some light on it.
03-16-2017, 03:30 PM - 1 Like   #6
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QuoteOriginally posted by gtxSeries Quote
Thanks!

I've been shooting a roll of Kodak Gold 200. I don't know how permissive film is, yet... so I've been just trying to be as precise as possible.
Negative film gives you a second chance, but slide film wont.

Good luck with your MX. It was my first film camera too....although for me we are talking nearly 40 years ago. I still have it and it still works a treat, in fact i have just orderd some b&w film to give all my old film cameras an outing.
03-16-2017, 09:58 PM - 1 Like   #7
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There is no manual mechanical SLR that has intermediate shutter speeds. You can set the shutter speed in between, but you won't know what the shutter speed will be. Electronic shutter cameras may give you in between shutter speeds in automatic, but when you set the shutter speed manually there shutter speed is set by fixed resistors or contacts. Mechanical leaf shutter lenses have a cam that may allow that.
03-17-2017, 02:55 AM   #8
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Thank you all for the help!

I'll be avoiding intermediate settings then. If I have to adjust the aperture, then so be it. That, or a missed shot, but I won't risk my camera.

03-17-2017, 02:10 PM   #9
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QuoteOriginally posted by Arvid Quote
...
No idea how and if that translates to the MX or other comparable cameras. If each shutter speed on a more advanced mechanical camera is connected to its own spring, I guess it should be avoided. Maybe someone who took the time to look at an exploded view of the MX or even took one apart could shed some light on it.
I think the metering circuit is all done with continuously variable resistors. So intermediate positions can get the meter to show a nice green light. But it's a lie - the shutter speed will be one or the other, and possibly lead to some problem. It shouldn't be a problem to set the aperture to an intermediate position, but most lenses already have clicks at half-stops.
03-17-2017, 05:26 PM - 1 Like   #10
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And just because it sounds like your almost done with the film, don't forget to push the button on the bottom before you rewind it.

You'll know if you forgot by the horrible shredding noise as you wind.

I may know someone who did that on his first roll...

-Eric
03-17-2017, 05:27 PM - 2 Likes   #11
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QuoteOriginally posted by Arvid Quote
I was especially worried about dialing an "intermediate" shutter speed on my older cameras (as in folders with compur shutters and such) which don't have any hard stops on their shutter dials until I finally got one that came with a manual. It explicitly says that it's totally fine to set the dial anywhere and it will gradually change the shutter speed accordingly, as it's all connected to one spring, except for the fastest speed that engages an additional "booster" spring on that model. To use that speed, it should be made sure to never set the dial between that fastest speed and the second one.
This is cool if one is using a Compur shutter.

QuoteOriginally posted by Arvid Quote
No idea how and if that translates to the MX or other comparable cameras.
It does not apply. The MX has a focal plane shutter where exposure is determined by the time between leading and trailing curtain release. (Both curtains travel at the same speed at all exposure settings.) The "slow" speed (1s - 1/30s) timing is done with a clock mechanism where each speed is half as many "ticks" as the next speed lower. At speeds greater than 1/30s on your camera, the timing is indirect by means of a mechanical escapement that sets the width of the slit between the two curtains. As a result, all speeds are discrete with no intermediate values possible. Edit: I am probably incorrect in regards to the "fast" speeds, based on some additional research.


Steve

Last edited by stevebrot; 03-18-2017 at 11:41 AM.
03-18-2017, 12:29 AM   #12
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My first roll is a complete success! Only one wasted shot, which I shot by accident.
By the way, the MX gives me an extra frame: it starts at 0 and finishes at 36. I was surprised at the lab. Now if I could load it in the dark...

My second roll is AGFA APX 400, which is in the lab. I'm excited!
03-18-2017, 06:25 AM   #13
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Some mechanical focal plane shutters have a continuous cam on the shutter speed dial (at settings above the slow speeds) so intermediate speeds will work. Many Leica and Leicaflex models mention that intermediate speeds will work, except for a gap where the low speeds start.
I don't recall how the MX linkage is though - been a while since I had one apart.
03-18-2017, 11:38 AM   #14
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QuoteOriginally posted by TomB_tx Quote
Some mechanical focal plane shutters have a continuous cam on the shutter speed dial (at settings above the slow speeds) so intermediate speeds will work. Many Leica and Leicaflex models mention that intermediate speeds will work, except for a gap where the low speeds start.
I don't recall how the MX linkage is though - been a while since I had one apart.
Thanks for this comment. It sent me back for a second look at available resources and also created a modest desire to find a junk body in order to actually see the action. From what I can tell, what you describe is probably true for the MX and most SLR shutters.


Steve
03-18-2017, 08:29 PM   #15
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QuoteOriginally posted by stevebrot Quote
Thanks for this comment. It sent me back for a second look at available resources and also created a modest desire to find a junk body in order to actually see the action. From what I can tell, what you describe is probably true for the MX and most SLR shutters.


Steve
That would explain why did that shot come out without being under or overexposed!
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