Sileem Posted July 19, 2015 Share #1 Posted July 19, 2015 Advertisement (gone after registration) Hi Approxiamtely how many 10 minute bulb exposures can i take with 1 set of batteries on M7 and on latest film MP? 1 Quote Link to post Share on other sites More sharing options...
Advertisement Posted July 19, 2015 Posted July 19, 2015 Hi Sileem, Take a look here Bulb Long Exposure on M7 -vs- MP. I'm sure you'll find what you were looking for!
Mark T Posted July 19, 2015 Share #2 Posted July 19, 2015 It sounds like you will have to experiment. I have never taken that many rolls (dozens, hundreds?), of ten minute exposures, in two cameras, counting till the batteries ran out. Or anything even remotely close to this. I would be surprised if anyone else had? Good luck with your research. Quote Link to post Share on other sites More sharing options...
Sileem Posted July 19, 2015 Author Share #3 Posted July 19, 2015 I asked because of this other topic where someone sayed the bulb exposure burned the M7 fresh set of batteries in 5 minutes. Another review wrote the M7 light meter turns off after bulb exposure over 16 minutes and turns back on when you end bulb shutter. 5 minutes looks like unreal given the fact they should last 50 rolls of film. If the batteries last under 1 month i would go definitely go with the MP or M-A. But the M7 stepless shutter speed in Auto mode appeals to me for low light. Quote Link to post Share on other sites More sharing options...
250swb Posted July 20, 2015 Share #4 Posted July 20, 2015 (edited) You don't need batteries in the MP (or I think the M7?) to make a bulb exposure, so a bulb exposure could be days, weeks, or years long. And the meter is switched off on the B setting for the MP. Neither camera has a sensitive enough meter for a ten minute exposure anyway, you would need a separate hand held meter, a reciprocity table, and a stop watch. Steve Edited July 20, 2015 by 250swb 2 Quote Link to post Share on other sites More sharing options...
semi-ambivalent Posted July 20, 2015 Share #5 Posted July 20, 2015 And after about fifteen seconds I'm not sure you even need a stopwatch. I carry a nice cable release just for these occasions, (which never seem to appear). s-a Quote Link to post Share on other sites More sharing options...
Sileem Posted July 20, 2015 Author Share #6 Posted July 20, 2015 You don't need batteries in the MP (or I think the M7?) to make a bulb exposure, so a bulb exposure could be days, weeks, or years long. And the meter is switched off on the B setting for the MP. Neither camera has a sensitive enough meter for a ten minute exposure anyway, you would need a separate hand held meter, a reciprocity table, and a stop watch. Steve How good is the M7 meter in auto mode around longer end, i belive the longest exposure is 32 seconds? I imagine, if there is no way to lock the meter value in memory and recompose and set tripod, im better of with external meter and bulb mode like you said. Quote Link to post Share on other sites More sharing options...
250swb Posted July 21, 2015 Share #7 Posted July 21, 2015 (edited) Advertisement (gone after registration) How good is the M7 meter in auto mode around longer end, i belive the longest exposure is 32 seconds? I imagine, if there is no way to lock the meter value in memory and recompose and set tripod, im better of with external meter and bulb mode like you said. I think you are missing something. Even if the M7 on Auto read an exposure of 30 seconds most films have a reciprocity curve that would take the required exposure into minutes. Reciprocity of film usually kicks in after exposures get beyond one second, although some films are immune up to a point. It means for a one second reading you may need to give the film 1.5 seconds to obtain a correct exposure, a 4 second meter reading it may become 12 seconds actual exposure you need. For example, Ilford FP4 has a reciprocity curve that means a 30 second meter reading requires the shutter to be open 155 seconds to make a correct exposure. You can find the reciprocity curve on the film manufacturers web site. You could fool the meter into giving a longer exposure to compensate for reciprocity by changing the ISO, but using the FP4 reciprocity curve the 32 seconds max exposure the M7 can achieve on Auto translates to a real reading of only 12 seconds indicated/metered exposure. In other words you could only usefully meter for a 12 second exposure and the rest of the exposure up to 32 seconds would be to compensate for the reciprocity failure of the film. This also applies to colour film, although some films are better than others, Kodak Portra for example needs a 77 second exposure for a 30 second meter reading. As you can see a 32 second maximum exposure in Auto for the M7 does not mean you will get a 32 second correct exposure, if left on Auto (for long exposures) you will get an underexposed negative. A tripod, a cable release, a hand held meter, a printed off graph for reciprocity for your chosen film, a watch, and either an MP or an M7 (or any other camera) set on 'B' is the way to do long exposures. And if the light changes during your long exposure you need to turn to gut instinct Steve Edited July 21, 2015 by 250swb 4 Quote Link to post Share on other sites More sharing options...
McGirton Posted July 22, 2015 Share #8 Posted July 22, 2015 How good is the M7 meter in auto mode around longer end, i belive the longest exposure is 32 seconds? I imagine, if there is no way to lock the meter value in memory and recompose and set tripod, im better of with external meter and bulb mode like you said. The M7 calculates exposure on auto mode up until 16 minutes (bulp meter goes to 999 seconds). Quote Link to post Share on other sites More sharing options...
250swb Posted July 22, 2015 Share #9 Posted July 22, 2015 The M7 calculates exposure on auto mode up until 16 minutes (bulp meter goes to 999 seconds). You'll have to let us have the page in the manual that says 16 minutes for auto exposure, I can only find 32 seconds as Sileem also notes. The 999 seconds in B is simply a display count, not metered, and beyond 999 seconds the shutter stays open and the count switches off to save batteries. Steve Quote Link to post Share on other sites More sharing options...
aesop Posted August 5, 2015 Share #10 Posted August 5, 2015 ...Sileem, in addition to the variables from your camera and lens, for all film (black and white negative, colour negative and slide), any exposures around and over the five second mark will more than likely result in some kind of colour shift or reduced density, or both. You are entering the joyful realm of experimentation. It is important to note that your results may not necessarily apply elsewhere. In other words, YMMV. So here's some real-world advice to add to the invaluable "gut instinct" mentioned by 250swb - ditch all the theory and run some tests. Preferably with the same equipment and roll(s) of film. Be thorough and methodical. Good luck. 1 Quote Link to post Share on other sites More sharing options...
rirakuma Posted August 5, 2015 Share #11 Posted August 5, 2015 Doesn't the bulb mode turn off the meter so it should not affect the batteries at all? Quote Link to post Share on other sites More sharing options...
aesop Posted August 5, 2015 Share #12 Posted August 5, 2015 (edited) Doesn't the bulb mode turn off the meter so it should not affect the batteries at all? ...correct, rirakuma - the OP also asked a supplementary question regarding the use of long exposures in the battery-reliant "Auto" mode. As mentioned above, the maximum possible exposure time in this "Auto" mode is 32 seconds. Edited August 5, 2015 by aesop Quote Link to post Share on other sites More sharing options...
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