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Photo Forum / Film Photography / 35 mm / September 2005Flashmeter newbie needs some guidance
I just got a flashmeter which the previous owner swears isn't working but it does turn on and seems to respond to light -- a single flash from a hand-held strobe caused it to display a reading -- so far that's the extent of my experimentation. I'm a very experienced photographer (5+ decades, I guess) and somewhat of an electronic engineer too so even opening it up and examining the circuit doesn't scar me. But I have never owned a flashmeter before and I was hoping for at least some website with general guidance on using one. Also, I've been thinking that I would use an old vivitar 283 as a light source to test the meter since it's more or less internally calibrated. Is this a good idea or should I do something else like actually take pictures with a DSLR and determine the correct f-stop and see what the meter says? Any suggestions appreciated. Norm > I just got a flashmeter which the previous owner swears isn't working but it > does turn on and seems to respond to light -- a single flash from a [quoted text clipped - 10 lines] > this a good idea or should I do something else like actually take pictures > with a DSLR and determine the correct f-stop and see what the meter says? You can't test a meter against an auto flash, as the flash will cut off when it believes the flash exposure is correct. You have to test your meter with a flash that outputs a fixed amount of power each time. Manual power setting, IOW. Set up a scene with white, mid-tone (grey/beige) and white, as well as some color elements. (Bowl of fruit, toys, etc.) Setup the flash on a stand. Distance must remain constant. Meter the flash with the meter close to the subject, dome pointing at lens. The flash __must__ be in a manual power setting mode (not an auto mode or TTL mode). Set the aperture per the meter (make sure meter and camera are at same ISO setting, assuming you're indoors, meter can be set to at any reasonably close shutter speed setting, eg: 1/60 .. 1/125). Shoot the shot and look at the histogram. If the highlight return is as low as even the center of the histo, chances are very good that the flash meter is correct. (Ideally the highlights would be right up to the right, but not likely, depends too much on your sensor). Examine the detailed image (on computer) to see how well the color looks. Experiment with aperture larger and smaller to get a feel for an offset between the meter and the DSLR. Repeat the experiment with neutral slide film (such as Sensia 100). Keep good notes. Have fun. Cheers, Alan  Signature-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm -- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm -- [SI] gallery & rulz: http://www.pbase.com/shootin -- e-meil: Remove FreeLunch. > > I just got a flashmeter which the previous owner swears isn't working but it > > does turn on and seems to respond to light -- a single flash from a [quoted text clipped - 45 lines] > Cheers, > Alan Thanks for the detailed procedure. I'm sure I'll have fun doing it ;-)) Norm >>Set up a scene with white, mid-tone (grey/beige) and white, as well as >>some color elements. (Bowl of fruit, toys, etc.) > > Thanks for the detailed procedure. I'm sure I'll have fun doing it ;-)) > Norm UR welcome. Note that above I meant "white, mid-tone and _black_" Cheers, Alan Signature-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm -- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm -- [SI] gallery & rulz: http://www.pbase.com/shootin -- e-meil: Remove FreeLunch. > >>Set up a scene with white, mid-tone (grey/beige) and white, as well as > >>some color elements. (Bowl of fruit, toys, etc.) [quoted text clipped - 3 lines] > > UR welcome. Note that above I meant "white, mid-tone and _black_" I'll probably include the Kodak 18% Gray Card that I've carried around in my bag for years without ever using it in the field. BTW, the 283 has a "full-power", manual mode that should be perfect for this test. Norm > I just got a flashmeter which the previous owner swears isn't working > but it does turn on and seems to respond to light -- a single flash [quoted text clipped - 15 lines] > Any suggestions appreciated. > Norm The tricky part is that the flash uses the reflected light from the subject while the flash meter (usually) uses the light directly from the flash. If you subject does not reflect the amount of light that the flash meter is calibrated for (for example 18%), the flash will see a different exposure than the flash meter. My suggestion is to set the 283 to manual full power. Measure the flash with the flash meter at a known distance (use a measuring tape). The f-stop that the flash meter should indicate can be calculated by dividing the guide number of the 283 by the distance between the flash and the meter. The Vivitar 283 has a guide number of 36 (@ 100 ISO), so when measured at 4.5 m you should get a reading of 36/4.5 = f8 from the flash meter (@100 ISO). Good luck, Menno "Joe Blow" <reply_to_newsgroup@nowhere.com> > The tricky part is that the flash uses the reflected light from the > subject > while the flash meter (usually) uses the light directly from the flash. If > you subject does not reflect the amount of light that the flash meter is > calibrated for (for example 18%), the flash will see a different exposure > than the flash meter. No, no, no! What a bunch of bullpucky. The flash meter is an incident meter. The OP has decades of experience. What is the friggin mystery here that a few tests won't reveal? Push the computer away and make it so. > "Joe Blow" <reply_to_newsgroup@nowhere.com> > [quoted text clipped - 8 lines] > > What a bunch of bullpucky. The flash meter is an incident meter. Exactly, the flash meter is an incident meter and the sensor in the flash is a reflective meter. That's why the two meters will see different exposures (different "amounts" of light) if the subject doesn't have the same reflectiveness as the flash is calibrated for. That's why the OP should NOT use the auto mode of the 283 flash. > The OP has decades of experience. What is the friggin mystery here that a > few tests won't reveal? Push the computer away and make it so. Nothing against a few tests with a camera. But just using your brain and the old fashioned guide number can save you some time and effort. Why do you think a flash manufacturer specifies a guide number? You might as well use it. Anyway, the OP has a digital SLR and I'm sure he'll be able to figure out if the flash meter's reading is trustworthy or not. > > I just got a flashmeter which the previous owner swears isn't working > > but it does turn on and seems to respond to light -- a single flash [quoted text clipped - 21 lines] > calibrated for (for example 18%), the flash will see a different exposure > than the flash meter. Well, I could use my Kodak 18% Gray Cards as part of the target, huh? > My suggestion is to set the 283 to manual full power. Measure the flash with > the flash meter at a known distance (use a measuring tape). The f-stop that > the flash meter should indicate can be calculated by dividing the guide > number of the 283 by the distance between the flash and the meter. The > Vivitar 283 has a guide number of 36 (@ 100 ISO), so when measured at 4.5 m > you should get a reading of 36/4.5 = f8 from the flash meter (@100 ISO). Yeah, I checked today while moving stuff from one camera bag to another and did indeed verify my recollection that the 283 has a manual (non-automatic) mode. Beyond the numerical stuff, I'm planning on using the D70 DSLR to verify exposures as well. Norm [SNIP] > Yeah, I checked today while moving stuff from one > camera bag to another and did indeed verify my > recollection that the 283 has a manual (non-automatic) > mode. An accessory for the 283, that at least recently was still available new, is the "Vari-power Module". This plugs in in place of the auto senso and gives you variable (manual) power from full down to about 1/32nd. If you're using the 283 manually with a flashmeter this is a useful thing to have (especially so if you have more than one gun and want to vary the ratio between them). Peter > [SNIP] > > [quoted text clipped - 9 lines] > (especially so if you have more than one gun and want to vary the ratio > between them). I'll check it out. My 283 dates from IIRC the late 70's so I'll have to see if it's sold separately. Thanks for the info Norm >I'll check it out. My 283 dates from IIRC the late 70's so I'll have to see >if it's sold separately. Why don't you borrow a flash meter that is known to be accurate, carry out a test flash with both meters and compare the readings? If you don't know anyone with a flash meter your local photo store or photo club might be able to help. Yep the vario-power module available separately but changes flash duration and some (not all) studio flash meters don't like the short flash durations. > > [SNIP] > > > [quoted text clipped - 19 lines] > > Norm Recently, Norm Dresner <ndrez@att.net> posted: > I just got a flashmeter which the previous owner swears isn't working > but it does turn on and seems to respond to light -- a single flash > from a hand-held strobe caused it to display a reading -- so far > that's the extent of my experimentation. It seems that it is doing something that it's supposed to do. [...] > Also, I've been thinking that I would use an old vivitar 283 as a > light source to test the meter since it's more or less internally > calibrated. Is this a good idea or should I do something else like > actually take pictures with a DSLR and determine the correct f-stop > and see what the meter says? Hmm. A roll of film would expose most issues with your flash meter. Set the flash on "manual", see what the meter reads, and shoot at that value +/- 1 or 2 stops in whatever fractions of a stop your camera allows. Regards, Neil > Recently, Norm Dresner <ndrez@att.net> posted: > [quoted text clipped - 16 lines] > the flash on "manual", see what the meter reads, and shoot at that value > +/- 1 or 2 stops in whatever fractions of a stop your camera allows. Actually I was planning on using a DSLR and getting instant results. Norm The problem with using a portable flash like the 283 is that flash duration (even on full power) might be quite a bit shorter than most studio units so I'd try to borrow a monolite from someone to use instead. > I just got a flashmeter which the previous owner swears isn't working but it > does turn on and seems to respond to light -- a single flash from a [quoted text clipped - 13 lines] > Any suggestions appreciated. > Norm > The problem with using a portable flash like the 283 is that flash > duration (even on full power) might be quite a bit shorter than most > studio units so I'd try to borrow a monolite from someone to use > instead. He should use the 283 on manual. I suppose it depends on the meter but I never had any problem reading small speed lights with any meter I ever used. Best to compare units via incident readings. -- dadiOH ____________________________ dadiOH's dandies v3.06... ...a help file of info about MP3s, recording from LP/cassette and tips & tricks on this and that. Get it at http://mysite.verizon.net/xico ____________________________ >> I just got a flashmeter which the previous owner swears isn't >> working but it does turn on and seems to respond to light -- a [quoted text clipped - 15 lines] >> Any suggestions appreciated. >> Norm > The problem with using a portable flash like the 283 is that flash duration > (even on full power) might be quite a bit shorter than most studio units so > I'd try to borrow a monolite from someone to use instead. That (shorter) isn't a problem. So there's no need to find a unit with longer flash duration (that. longer, could be a problem). |
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