Considerations and calculations for stacking on LG format film
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Garry Edwards
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It's a very simple process, the important thing is to totally exclude all unwanted ambient light, which means that you must work in total darkness.
There are two distinct and discreet ways of doing it . . .
1. Use multiple exposures in order to create more power than a single flash can provide - 2 flashes = 1 stop, 4 flashes = 2 stops, 8 flashes = 3 stops etc. The shutter must of course be open throughout the process. The flash will be in exactly the same place throughout. The flash will of course be set to full power.
2. Use multiple exposures in order to create the effect of more flash heads than you actually have, in which case the flash head is moved between flashes, adjusting the power between shots as necessary. Start with the flash power at the lowest required setting, and increase it if necessary in different positions. You must do it that way round because, if you turn down the power between shots, the flash head may produce more power than that set on it.
There are two distinct and discreet ways of doing it . . .
1. Use multiple exposures in order to create more power than a single flash can provide - 2 flashes = 1 stop, 4 flashes = 2 stops, 8 flashes = 3 stops etc. The shutter must of course be open throughout the process. The flash will be in exactly the same place throughout. The flash will of course be set to full power.
2. Use multiple exposures in order to create the effect of more flash heads than you actually have, in which case the flash head is moved between flashes, adjusting the power between shots as necessary. Start with the flash power at the lowest required setting, and increase it if necessary in different positions. You must do it that way round because, if you turn down the power between shots, the flash head may produce more power than that set on it.
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Doesn't work like that because of reciprocity, yes 2 flashes i just about 1 stop, but you need 5 or 6 for 2 stops,10 or 11 for 3 stops, the exact number will depend on the particular film used.
It's exactly the same with multiple daylight exposures as well.
Ian
Garry Edwards
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Yes, reciprocity failure is a factor, but not a massive one in my experience.
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How fast does a flash fire? Lets say 1//1000 of second? Seems you can pop off alot and easily hit 4+ stops before you hit 1 second or more total exposure
1 flash 1/1000
2 flash 1/500 total duration
4 flash 1/250
8 flash 1/125 duration etc etc
Is this not correct?
Ha writing it out actually looks about right, TIL!
1 flash 1/1000
2 flash 1/500 total duration
4 flash 1/250
8 flash 1/125 duration etc etc
Is this not correct?
Ha writing it out actually looks about right, TIL!
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Adjusting the power of a flash does not correlate to the length of each flash exposure, as you are assuming, it's the power discharged from the capacitors.
In fact the flash duration is the longest at high power, and shortest at low power, so the opposite.
Ian
In fact the flash duration is the longest at high power, and shortest at low power, so the opposite.
Ian
Garry Edwards
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Let's not go down a rabbit hole and take this thread off track - but what you say is only correct with IGBT technology flashes, the opposite is true with conventional technology ones.
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Almost all modern camera hot shoe flash guns use IGBT technology as do a great many of the newer monolites and flash packs, It's fairly standard these days,
Yes, one at 1/2 & 3 at 1/4.
Ian
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Do you mean two at 1/4 Ian?
Garry Edwards
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You're right when it comes to hotshoe flashguns, but as most of them only produce around 70j and LF cameras are typically used at around f/45, it didn't occur to me that anyone would want to use them for this purpose.
With studio flash (which sadly is the one subject that I know anything about) there are plenty of old ones in use, and over 70% of all new sales are conventional technology - most people want IGBT but have more sense than money, and won't pay the inflated prices.
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If your flash is IGBT, this might work, but you’d need low power settings. Because of recycle times
Which, if you’re simply popping them off to increase exposure, it becomes pointless.
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What are the ideas? I haven't done it with large format, but I don't see why it would be any different than with any other film camera (or digital for that matter). Large format does increase the amount of light you need for each exposure, but that's all (AFAIK).
In the most simple form you can simply limit the flash's impact on the scene for each exposure (i.e. hard light and shadows), with the light illuminating the opposite area for a second exposure. Or just as simply, mask off the lens so that one area of the scene doesn't reach the film; and flip the mask for a second exposure.
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In answer to various points my flashes are four old Bowens and two old elinchrom, I prefer the bowens that I have used here previously and which I have a flash cable for, I am not going to trying wizardry with a 70's camera (guess) with an even older lens and shutter.
I want to photograph the same thing in three different positions with lighting (and shadowed) from three different positions.
I want to photograph the same thing in three different positions with lighting (and shadowed) from three different positions.
sk66
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If the positions do not overlap the easiest is probably a lens mask... it needs to be as close as possible to the front element.
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I had not thought of that thanks Steven
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LF lenses have typically been optimised for use at f22, that goes back to Carl Zeiss Jena lenses pre-WW2. With 5x4 you begin to run into diffraction limitations at f32 & f45, that just means sharpness may be dropping off.
A few years ago someone analysed the work of John Sexton, one of his books has all the exposure details for every image, he did shoot a few images at f32, and one or two at f45, the majority were f22.
Should we use f32 or f45, you have to know your lenses, yes there are occasions. It's a compromise, you'd really only see a difference in very large prints off 5x4 negatives, but then how large do we print. In my case it's been up to about 17ft.
When it comes to studio flash . . . . .
I've been using Elinchrom studio flash for about 45 years, and it's all IGBT, and regular prices. I can't fathom why you even bothered to go off on that IGBT tangent. It's so totally irrelevant.
Do you not understand that IGBT is actually current conventional technology?
Ian
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Ian,
You're an expert on LF, I'm not and you may be right about diffraction limitation, but the physics argue otherwise and I've normally shot at around f/45 on 5x4, f/64 or f/90 on 10x8, without any problems, and some of those shots have ended up as billboards.
As for IGBT, there was a rumour back in about 2013 that Elinchrom had managed to make an IGBT flash head, allegedly designed for them in China, everyone in the trade knew about it but nobody actually saw it. The very first IGBT studio flash was made in a very small factory in uptown Shenzhen. I looked at it, was very interested but didn't have confidence in the factory capability. Someone else did then import that technology but from an even smaller factory, for a few weeks. all of the flash heads broke down and the Company went bust, leaving lots of debts.
The Company I was working with then introduced IGBT studio flash later that year, and we were the first with one that worked, so your belief that Elinchrom (or anyone else) has been producing IGBT for 45 years is just a bit off
You're an expert on LF, I'm not and you may be right about diffraction limitation, but the physics argue otherwise and I've normally shot at around f/45 on 5x4, f/64 or f/90 on 10x8, without any problems, and some of those shots have ended up as billboards.
As for IGBT, there was a rumour back in about 2013 that Elinchrom had managed to make an IGBT flash head, allegedly designed for them in China, everyone in the trade knew about it but nobody actually saw it. The very first IGBT studio flash was made in a very small factory in uptown Shenzhen. I looked at it, was very interested but didn't have confidence in the factory capability. Someone else did then import that technology but from an even smaller factory, for a few weeks. all of the flash heads broke down and the Company went bust, leaving lots of debts.
The Company I was working with then introduced IGBT studio flash later that year, and we were the first with one that worked, so your belief that Elinchrom (or anyone else) has been producing IGBT for 45 years is just a bit off