Am I in sync, or what? : LUSENET : Large format photography : One Thread

This one has me stumped again. My question is about using my electronic flash (Sunpak 4000 AF)on my 8x10 HOBO as fill flash. The mounted lens is a Schneider S/A 121 f8 (black version). My exposure for my test shot calls for 1/30th @ f22. I am placing my flash on FULL manual . Remember that I am only concerned with flash within the flash's capability. About a 10 foot range. The lens has a Synchro-Compur, a sync post, but no markings to indicate which shutter speed is the sync. This is an outdoor sunny day exposure. I am exposing one sheet of film with, and the other without flash. After developing the negatives and letting them dry,I cannot identify the one that was exposed with the flash. Yes, I made sure the flash went off . So!, my question to all the large format gurus' that have been there and done that is: 1-Is my flash not powerful enough? 2-Is it because of my f stop (f22) 3-What f stop if not all is the sync one? :and just for information sake this home made hobo was designed for street shooting, and f22 is a necessity to cover the complete 8X10 format corner to corner. Thank you for any information you can give me.

-- Dan Kowalsky (, February 24, 2001


Leaf shutters, aka between-the-lens shutters, synch at all speeds. Does you shutter have a MX switch? If so, you should set this at X for electronic flash. The M setting is for flash bulbs and will fire an electronic flash too early, before the shutter opens.

You should be able to test the synch without using film. In a dim room, point the flash and lens at some white paper, then trip the shutter while looking through the lens. If everything is working properly, you will have no difficulty seeing the bright flash through the lens.

-- Michael Briggs (, February 24, 2001.

Dan There is the possibility that your flash did not synch, and I agree with the previous poster that your leaf shutter synchs at all speeds. But I have taken thousands of flash shots outdoors and I suspect that if it was quite a sunny day outside you are not going to see much fill, and especially so when you have used f22 as an f stop. You did not say what your shutter speed is, but REMEMBER, your flash is firing at a speed that is far faster than any shutter speed you have on that lens. Therefore, the only means of controlling that flash is with f stop. F22 is a very small f stop, and so you probably did not get much exposure out of the flash itself. I would be curious to know what your shutter speed was. At any rate, I am betting that your ambient exposure was quite good, and due to the small f stop you did not get much flash exposure. What I would do would be to contact print both of those negs. Look at the shadows in your subject. If you contact them both for exactly the same time I think you may see just a tiny bit of difference in the shadow area but not much if any difference in the highlight area. That is because light is additive. Good luck. Kevin

-- Kevin Kolosky (, February 24, 2001.

Dan: There should be a sync selector beside the flash connector on the shutter. Make sure it is on "X". The selector is on the side of the shutter. If you are shooting people, look to see if you can see the flash catchlight in their eyes. I agree that the aperature is probably too small to see much difference at 10 feet unless you have a pretty hot flash. Flash fill is great with a leaf shutter camera. I like to set the flash on auto, and the ISO on the flash gun one step higher than the film, ie., ISO 800 if you are shooting with 400 ISO film. It gives you one stop less of flash fill than that of the main exposure.


-- Doug Paramore (, February 24, 2001.

This doesn't address the sync issue exactly, but will a Sunpak 4000 come anywhere near covering the 107-degree angle of view (diagonally) of a 121mm lens on 8x10? I would just look for the effects of the flash in the center of the frame. Then you have the issue of the normal light falloff from the lens, which will make the center brighter than the corners by about 1-2 stops anyway, so the flash which probably doesn't cover the whole field would just exaggerate that effect.

I think if you want to use flash with this setup, you'll need a powerful barebulb flash to cover the wide angle of view or maybe two flash units angled in a V pattern.

-- David Goldfarb (, February 24, 2001.

Sunpak's web site indicates that this is a zoom flash that works with the 35mm equilvalent focal lengths of 28-80mm with guide numbers from 80-132 feet (I assume 100 ISO). I assume that you have it set to the 28mm to get as wide as possible, so the guide number is the lower number (80). So at f/22, your flash range for full exposure is less than 4 feet (80/22 = 3.6 ft). You get 1 stop down at 5.1 feet, 2 stops down at 7.3 and 3 stops down at 10.3.

You said your flash had a range of 10 feet (at f/8) but I'm not clear how far your subject is. Is it at 10 feet? If so, three stops down of fill will probably not be noticable.

You would need a flash with 35mm equivalent coverage of a 14mm lens to cover the 121mm on 8x10.

-- John H. Henderson (, March 02, 2001.

Oh....and this is assuming ISO 100 film. If you're using slower, the distances are even shorter.

-- John H. Henderson (, March 02, 2001.

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