Minolta mod to 1/50 shutter speed

<p>Hello everyone,<br>

I am a user and abuser of Minolta manual cameras and lenses. I have been curious for some time if it is possible to open up the electronics on the Minolta XD/XG/700/570s etc. and adjust the available shutter speed options.<br>

Just to explain: These cameras all step directly from 1/120 to 1/60 to 1/30. As you may know, for the cinematographer, a camera shooting at 24fps with a 180 degree rotating shutter gives you a shutter speed of 1/48 sec. This is commonly rounded off to 1/50. It would be extremely useful for doing true light studies or checking exposure (say, with a NPC polaroid back) to have a 1/50 (or 1/48) shutter speed option.<br>

Is it possible to get the cameras of this era and brand to do this? Even if it ruined the camera otherwise it might be worth it to have a dedicated system.<br>

Now, certain solutions are somewhat obvious: there are plenty of more modern 35mm slr cameras with a built in 1/50 shutter speed. Naturally, but I'm cheap and I want to use my exiting tools and lenses if at all possible.<br>

There also must be a mathematical solution. 1/48 is, I believe, 1/5 of a stop below 1/60. What would be the best way to use that figure to aid in exposure checking? I'm sure a smarter person than I could make a neat chart cross-converting standard cinema exposures to the available shutter speeds and polaroid film stock ASAs. <br>

The one other thing that occurs to me is to take advantage of the integrated flash-snyc settings. I'm not totally clear on how all that works, but I am peripherally aware that certain older Minolta systems have a 1/50 sec flash snyc mode. Might we be able to do something with that? I bet that would only work on a select few bodies (sr/srt series, not the newer models that I use).<br>

Am I nuts? Would love some camaraderie/help. Thanks!<br>

-Jordan </p>

<p>one solution is to get an sr-t blank (the cheapest one you can) and then simply adjust the spring tension, e.g. you can easily bring 1/30 to 1/48</p>

<p>On electronically controlled cameras, shutter speeds are set by the electronics and cannot be changed that easy, especially if it's a digital control system.<br>

On mechanical cameras, it's easier. Speeds are controlled by a speed escapement which is set by a cam disk. Filing down the 1/30 sec cam will bring your camera to 1/50.<br>

Anyhow, I think the better solution is to compensate the speed error between 1/60 and 1/50 by adjusting the aperture accordingly.</p>

 

<p>One half of a stop below 1/60th is 1/45th. One third of a stop below 1/60th is 1/50th. While setting the shutter to 1/50th may align it with your cine camera shutter, unless your lens has hard stops it won't matter in terms of exposure. Don't many cine lenses have infinitely variable apertures? The best mod would be to open up your Minolta lens and carefully remove the ball bearing that generates the click stops. This may make metering with this lens a strange affair, but I am assuming you will be using a hand-held meter to set the cine camera. Simply set your still camera aperture to be 1/3rd of a stop more open than the cine camera and the exposures should be identical. All of that said, I am not sure if an NPC back gives 100% exact exposure or if there is some light lost in the fiber optic grid. If that is the case, then it may very well be that the NPC back will yield and identical exposure. But I am not an authority on such things. You should also be aware that Polaroid and Fuji materials do not behave exactly like other films and while they are good for seeing some things, the instant images will not be identical to what the cine camera captures.</p>

<p>If you had a way to measure the shutter speed you could mount a preset lens, such as the Rokkor QF 50mm macro and use the stop down ring to continously adjust aperture until reaching 1/50 second.<br>

If you can't find the preset Rokkor, one of the old 35mm or 135mm T-mount presets that were often included with "deluxe" SLR kits would also give infinitely variable f-stops.</p>

<p>At one time I has a 35/4 pre-set Rokkor. For some reason it fit an SR-1S pretty well but did not fit easily on an X-370 I had at the time so I got rid of it. I now have a 50/3.5 pre-set Rokkor macro lens as well as a 135/4 TC Rokkor pre-set. The 50 is decently sharp even if it doesn't have the most modern coating. I think MInoolta used to have a system of creative ards which would plug into some of its AF SLR cameras. If you got one of those cameras you might be able to have someone program a card to give you the shutter speed you're looking for. Another option would be to use the exposure compenation dial on a camera like the X-700.</p>

<p>If you can get hold of an Olympus OM10, the manual adaptor which plugs in to give speed control is said to be just a series of resistors of different values. If you could replace this with a variable resistor you could perhaps get continuously variable shutter speeds.</p>

<p>Thanks everyone for the creative suggestions.</p>

<p>I think we hit it on the head when we get into continuously adjustable aperture rings. I love all my old lenses, but unlike the super-high-quality Zeiss/Cooke/Angenieux lenses we use on set, they have hard clicks which only allow compensation in 1/2 stops (& not always that). I would feel awful cracking open those beautiful Minolta lenses just to pull off this one specific operation. So simply compensating down 1/2 or 1/3 or 1/5 of a stop on the lens is out.</p>

<p>I am intrigued by the suggestion that my NPC back might have some natural light loss. If it in fact does lose something in the 1/2-1/5 range we're done before we even get started! Does anyone have some insight into this issue?</p>

<p>The other simple solution I didn't think of at the onset would be to compensate via filtration. As you point out, I would most likely be metering with external meters so the in-camera exposure discrepancy wouldn't matter. The question is: Is there an ND or some other standard filter which cuts out the right amount of light? I guess an ND.15 would get us to 1/45 sec. That's not bad, but is there something that gets us exactly 1/48 or 1/50 (down from 1/60 I assume, but you could really start anywhere on the dial)?</p>

<p>Maybe it would be helpful to get specific with this. Here's what I'm really working with:<br /> NPC Polaroid Proback for Leica R4-R7 (same rear door as the Minolta XD series)<br /> Minolta XD11 (or 7, or 5)<br /> I realize that we're maybe in electronic shutter territory with the XD series, but read this:</p>

<p>"Electronically controlled stepless shutter speeds from 1/1000 to 1 second for automatic modes plus stepped speeds from 1/1000 to 1 second plus “B” in metered manual mode. “X” sync setting for 1/100 sec, plus fully mechanical operation at “O” (1/100 sec) and “B”." (from- http://www.rokkorfiles.com/XD11.html)</p>

<p>What does "stepless shutter" mean? It's not magically continuously adjustable somehow, is it?</p>

<p>Note the 1/100 sec sync settings. If we can take advantage of that feature (without an actual flash) then we're exactly 1 stop above where we need to be. That wouldn't ultimately be a bad solution. Any way to do that? Maybe that "O" setting he mentions?</p>

<p><br />Also note: "plus fully mechanical operation at “O” (1/100 sec) and “B”." Does this mechanical option give us an opportunity to make a more direct physical mod as some of you describe? Or is this my answer to a 1/100 solution?</p>

<p>Thanks again!<br /> -Jordan</p>

<p>ND 0.1 would be 1/3 stop, ND 0.15 would be 1/2 stop.<br>

Of course, if you are doing test exposures for cine films, realize that cine lenses are generally marked in T-stops, not F-stops, giving more accurate exposure. Depending on the number of elements and coating, your Minolta lens at f/4.0 might really be T/4.2 or T/4.5.</p>

 

<p>Jeff- The Custom Function card for the Maxxum 7000i/8000i allows shutter speeds to be set in half stop increments. I use one of my 8000i. Instead of the sequence being 1/30, 1/60, 1/125 it becomes 1/30, 1/45, 1/60, 1/90, 1/125. Don't know if 1/45 is close enough to what Jordan needs or not.</p>

<p>John,<br>

Thanks for pointing out the T vs. F-stop issue. I am fully aware of the theoretical difference between the two figures, but I never heard anyone quantify the discrepancy as you have here. </p>

<p>I know that cinematographers for years and years were using polaroid systems for checking exposure. I think they were generally using Land Camera style or Konica Instant Press rigs, not the 35mm lenses and bodies we're discussing here. So would F vs. T-stop only be a problem given the added complexity of Minolta Lenses or has it been there all along? </p>

<p>If this specific scenario indeed presents particularly skewed readings because of the F-stop scale, can you offer any potential solutions? Is there a means of actually measuring my lenses for light loss due to element groups and lens coatings? Are there any published records converting my manual lens markings from F into T? Is there maybe a rule of thumb one can use by counting sets of elements and/or types of multi-coat?</p>

<p>I just wanted to post a quick follow-up to this discussion. I guess it really does pay to read the manual some of the time. </p>

<p>On the Minolta XD-5 (and 11 and 7) there are two flash sync settings: X (electronic) and O (mechanical) </p>

<p>The flash sync speed for these models is 1/100 sec! Hooray, an easily divisible relative of 1/50 sec. We can now easily meter for 24fps (using our external meters), open up one full stop, and snap a quick polaroid to check our exposure. </p>

<p>Anyone want to rain on my parade? Is there something I'm missing?</p>