I've just ventured into the land of strobe photography with a 4x5 and am having problems with underexposure. Right now I'm using a Canon Speedlight 550EX as my strobe, which I realize isn't ideal, but I was hoping with multiple pops I could get away with it for a while so I can choose a studio strobe system. I'm taking a simple tabletop photo of glass of wine and wine bottle. I'm using Polaroid Polacolor Pro 100. I have a Sekonic L-608 light meter.

If I point the flash directly at the subject and take the flash reading my exposure basically turns out right -- I just have really bad shadows. So, I decided to try a bounce flash -- I have 9-ft. white ceilings. I set the light meter for mutiple flashes and I did 3 pops to get an aperture of f22 (light meter sitting in the middle of my composition). So, I set the camera for f22 and took the photo -- because of the slow recycling times on the flash the total exposure ends up being a little over 1 minute. The photo came out seriously underexposed (I tried 3 or 4 photos, just to make sure it wasn't me doing something monumentally stupid), so I tried 4 flashes and the light meter told me f32 (but I left the camera set at f22 to minimize variables) -- the photos between 3 and 4 flashes look virtually identical.

I'm at a complete loss as to what I'm doing wrong. Any ideas are greatly appreciated -- I've been beating my head against the wall on this.

Thanks!

-- Jennifer Waak (jen.waak@visi.com), July 15, 2001

Answers

If your meter is telling you that 3 pops = f/22 and 4 pops = f/32. Something is definitely wrong with either your meter or your technique. Sekonic meters are not known for their low light responsiveness. and this is a low light situation.What does it indicate your f-stop should be for just one pop of the flash?

Let's say that your meter , when you measure just one pop, tells you that your camera should be set at f/5.6 for ISO 100 material. To get f/8 you'll need 2 pops. To get f/11 you'll need 4 pops. To get f/16 you'll need 8 pops. To get to f/22 you'll need 16 pops. Now wait! it gets worse! I have found over the years that if the meter is telling me I need 4 pops of the strobes to get a certain f-stop, I have to add an addition pop for each 4 the meter is indicating a need for. So if my calculations tell me I need 16 pops, I'll start with 20 pops, and yes I do see a difference with just that extra 1/4 stop of light.

So try reading a single pop and then extrapolating from there, doubling the number of pops from the previous f-stop

-- Ellis Vener Photography (evphoto@heartstone.com), July 15, 2001.

Jen, The harsh shadows are created by the point light source. This is why we use softboxes of all sizes. The larger the lightsource, the softer the light when shooting close. You don't have to go out and buy a softbox right now... for starters, 9' ceilings, your wasting valuable light and spreading it way to far! Get yourself a large (20x24 or larger) piece of foamcore and suspend it horizontally just out of camera range above your set. Bounce your flash off of that. If you "feather" (tilt the foamcore towards the camera maybe 45 degrees from the horizon) you will get a darker, graduated background. The other alternative is to make a shoot through panel out of PVC tubing and a transparent white material you can get from the fabric store. Make it 3' square or larger. These can be bought commercially also but it is cheaper to make your own. As far as your multiple pops, your getting into the realm of reciprocity failure. You'll either have to open up a few stops or pop a few more times.... that is if your pictures are nicely exposed with the straight flash and one other thing, stop with the head against the wall... it puts dents/holes in the walls and will cause dane bramage! :) Cheers

-- Scott Walton (scotlynn@shore.net), July 15, 2001.

Hi Jennifer

Are you holding the light meter in direction to the ceiling? Thad gives you wrong f stops! The meter should looking in direction to the lens not to the wonderfull white reflecting ceiling! Good light, Armin

-- Armin Seeholzer (armin.seeholzer@smile.ch), July 15, 2001.

Jennifer:

One f-stop is doubling or halving the amount of light. So if 3 pops is f/22, then 6 stops MUST be required for f/32. The difference between 3 and 4 pops is about 1/3 f-stop which is right at the limits of detectability.

-- Glenn Kroeger (gkroeger@trinity.edu), July 15, 2001.

Thanks for all of the great responses so quickly!

Yes, it is a low-light situation. I turned off the light in that room to avoid all of the reflections of the light bulbs.

Last night one pop gave me f11, 2 was f16, 3 was f22, 4 was f32. I had remembered an old post of Ellis' stating that you basically double the number of pops to open up a stop, so this didn't make sense to me (hence the experiment last night).

I just went and re-tried testing my exposure. With good room light the fstops went as follows: 45, 64, 90, 90, 128. When I turned off the room lights (but I now I have a lot more ambient light because I have windows) I got 32, 45, 45, 64, 64, 64, 64, 90.

Armin, BTW, you were right. I did have my light meter pointed towards the ceiling -- when I re-ran my tests I found it made no difference but it's still a good habit to get into.

I just ran a new set of Polaroids with the room lights off (so, the 32, 45, 45, 64, ... sequence). With 4 pops my photo was so dark it was almost as if I left the lens cap on (I could just see shadows of the subject). So, I took Ellis' advice and added 4 pops, for a total of 8. Again, everything was really dark. I reshot once again with the flash pointed directly at the subject, which got me back to the problem of having too direct of a light source, but at least the photo was well-exposed -- verifying that the light meter and I seem to work correctly for a single flash.

I'm going to try Scott's advice and play with some sort of diffusion; I knew that was an option, I just wanted to see how well my Speedlight was going to hold up for this sort of work and I think my conclusion is "not well".

This leads me to a follow-up question. I've been reading everything I can about studio lighting and have basically decided on a head and pack kit (because I want to have an overhead light and that seems precarious with a monolight). I think something around 1000 w/s to start and a couple of heads. I was leaning towards Dyna-Lite because of the weight -- right now I have no plans to travel with it, but less than a year ago I said I'd never shoot anything other than 35mm and bought a 35mm darkroom so I don't want to make that mistake again. But, Speedotron Black Line seems to have an advantage because of the interchangable reflectors. I can't find much on Elinchrome or Balcar, other than Ellis is currently using Balcar and loves it. I can rent everything except Balcar to try, but never having used studio lights I'm not sure of the value in that -- it took me a long time after moving from point-and-shoot to SLR to figure out what I liked and didn't like about my SLR and am sure it would be the same way with studio lighting. Right now I'll only be using the lights for table-top still life photography in my home; I'd also like to start doing architectural photography (where I guess monolights would win out). I have no intention of doing portraits, or at least not in any sort of volume. While this is just a hobby now, I would like to develop the skills and equipment to be doing this professionally (at least part time) down the road. Can anyone help me sort through the differences between the brands I listed above?

Thanks again!!!

-- Jennifer Waak (jen.waak@visi.com), July 15, 2001.

You say you are shooting 4x5.

Your meter is probably correct, but I wonder if you have made an adjustment for the bellows factor, or if you are filtering have you included a filter factor.

I think that a close up tabletop with bellows extension would require at least one more stop of exposure. Once you calculate the bellows loss you can adjust your meter to compensate if you wish.

Just one suggestion.

Bill

-- Bill Smithe (bs2@aol.com), July 15, 2001.

i always look for the simplest answer first. is your shutter set on "t" or something else? just a thought.

-- adam friedberg (asfberg@hotmail.com), July 15, 2001.

I completely forgot about the bellows factor! What I would give for TTL metering right now. :-) That's probably part of the problem, but not all of it since my single-flash, direct light source photos are coming out more or less OK (minus the terrible shadows). I'm not using any filters.

I do have my camera set to "T" -- I click it once to open the shutter and a second time to close it (between time I'm sitting there and repeatedly firing my strobe).

I'll try a new set of exposures with the bellows factor accounted for later today.

Thanks for all the new ideas!

-- Jennifer Waak (jen.waak@visi.com), July 15, 2001.

"Last night one pop gave me f11, 2 was f16, 3 was f22, 4 was f32. I had remembered an old post of Ellis' stating that you basically double the number of pops to open up a stop, so this didn't make sense to me (hence the experiment last night)."

If one pop is f11, two pops should be f16, but it'll take FOUR pops to get to f22, 8 pops to f32, 16 pops to f45.

-- David Grandy (dgrandy@accesscable.net), July 15, 2001.

An experiment. If the meter read f/11, did you try to make an exposure at f/11?

-- Ellis Vener Photography (evphoto@heartstone.com), July 15, 2001.

Don't forget the bellows factor!

Also, you could be getting some short-exposure reciprocity failure; the flash duration may be 1/1000 or shorter.

I know your initial reaction is to buy a powerful flash, but in working with large format and tabletop subjects unless you spend a huge amount of money on a high-power pack you'll still be working with multiple pops, just not so many of them. By high-power I'm thinking of 2400 w/s or more.

-- John Hicks (jbh@magicnet.net), July 15, 2001.

Jennifer, as david says it should be 8 pops at f32...FWIW, we do most of our studio shooting at work in terms of mulitple pops...we just shut off the modeling lights, and do the multiple pops in the dark with the lens on T...sometimes we don't even close the lens, just change holders, wait for things to settle out & then continue...and we will shoot on location this way as well, if we have to either by "beating" the available light with the strobes, or by covering the lens during recycling...you can never have enough power when you shoot 4x5....we use 2 2400 ws speedotron packs (blackline), and an 800....multiple pops are a convenient way of bracketing as well...but, you do need to take bellows factor in effect, as well as the subject matter....for instance, glass bottles etc...will be hard without a modeling light...not a problem for exposure really, but more of a general lighting problem. I have a Dynalight 1000 ws pack myself, and while this is great for small & medium format, when I use it for tabletop 4x5 work, I get into many multi-pops...like a minmum of 8 at least, for a basic shot...so, I agree that you might need at least 2400 ws minimum if you do this alot....we also don't use any fancy meters, just basic Sekonic models, all you need is to get the basic exposure, you can figure the multiple pops out from that...but having a flat disc diffuser, and knowing how to use the meter is important, as well as using Polaroid....

-- DK Thompson (kthompson@moh.dcr.state.nc.us), July 15, 2001.

I really appreciate the feedback from everyone, this has been great! I calculated the bellows extension factor, which came to 1.1 since I have 22cm of extension and a 210mm lens (22 squared divided by 21 squared).

I ran a new set of tests. First I set up my strobe so my light meter in single-flash mode registered an aperture of f11. I took an exposure -- looked pretty good. I skipped f16 and took another at f22 with 5 pops (it takes 2 to get to f16 plus one additional pop for every four pops, per Ellis). Again, it looked pretty good. I took one last exposure at f32, using a total of 10 pops. Again it looked pretty darn good. To accomodate the bellows factor I actually used approx. f20 and f29 instead of f22 and f32.

I know I haven't yet accounted for reciprocity failure, but at least the subject matter is identifiable, which is a far cry from where I was last night.

And, I'm still looking forward to getting a set of studio strobes for faster recycling times and more sophisticated lighting setups.

Thanks again to all.

-- Jennifer Waak (jen.waak@visi.com), July 15, 2001.

Since you are shooting polaroid and are in an experimenting mood, how about using multiple pops to fill-in the shadows? You already got a picture with correct exposure (and ugly shadows) using a single pop. Well simply add another pop from a different direction to fill-in the shadows. This might give you a more interesting look too, sort of simulating a multiple strobe setup. Good luck! (And how about posting your photo here once you done ;-)

-- Andreas Carl (andreas@physio.unr.edu), July 16, 2001.

Are you sure about that bellows extension? Unless your 210mm lens is a telephoto then 220mm of extension should get you into focus at around 4.5m or 15ft. That doesn't sound like a table-top shot of a wine glass and bottle to me!

As others have said, this definitely sounds like a metering and/or reciprocity problem. You seem to be combining flash and ambient light and depending on the relative intensities that would very likely explain the strange scaling. I would definitely try to maximise the light from the flash by bouncing it off a reflector much closer to the subject.

If you can shut out all ambient light then the multiple flash thing should work easily enough, but I would just meter one flash and recalculate the number required for the f-stop in use using the doubling sequence. Even then, I'm still not sure how well Polacolor Pro 100 handles a large number of low intensity flashes (not something I've tried with it).

-- Huw Evans (hgjevans@hotmail.com), July 16, 2001.

Huw, quick question for you. How did you determine that I should get into focus around 15 feet? When I did the bellows factor calculation I did think that that seemed quite short, but I just went back and looked at the camera again, and it is definitely set at 22cm.

While the image isn't as sharp as I would like (and another thing to work on), the focus is fairly good. Could the fact that I'm using some tilts change how far my bellows needs to be extended?

-- Jennifer Waak (jen.waak@visi.com), July 16, 2001.

Jennifer, the standard optical formula relating focal length(f), subject distance(u), and bellows extension(v) is 1/f = 1/u + 1/v [put another way, that is u = fv/(v-f)]. That is for a 'thin' lens, but it works fairly accurately for typical LF lenses, which have multiple elements and groups. You measure the distance from the film plane to the optical centre of the lens, or where the aperture is. It doesn't work for telephoto designs, but I imagine your 210mm is not one of those. If it is a telphoto that could account for the apparently short extension. In that case I would calculate the exposure compensation by considering the magnification at the film plane - if the magnification is m, then multiply the f number by m+1 to get the new effective f number.

If, as I assumed, it isn't a telephoto then I am mystified. The tilts shouldn't make too much difference, although the level of illumination will vary very slightly across the film plane. Simply measuring the distance between the film plane and the centre of the lens should still give a result that fits the formula fairly accurately.

I hope that helps, but I've a feeling that the mystery is only deepening - I can certainly see why you were beating your head against the wall!

-- Huw Evans (hgjevans@hotmail.com), July 16, 2001.

I don't know if this is going to matter or not, but I've never had much luck with accurate proofing on color polaroid materials...I've found that the b&w films were much better in terms of speed matching...so unless polacolor itself is the final product, you may have better luck with type 54 or 55....type 55 is nice because you can check focus on the neg easily, and the short range of the print matches up to transp. film well...but like I said, forget this if the polacolor print is what you want.

-- DK Thompson (kthompson@moh.dcr.state.nc.us), July 16, 2001.

The end goal is actually a transparency. I'm using the polaroids for doing things like checking shadows, verifying approximate exposure, checking composition, and checking focus. I've read to expect the colors to be off slightly and the exposure won't match quite right either (I can't remember which way the exposure will be off and I don't have my notes in front of me), but it is a good tool for getting a good overall sense of how the final photo will turn out. Is this a fair statement? Since I think sharp focus will ultimately be my real challenge in large format should I be using a different type of Polaroid or just bite the bullet and start shooting and exposing more transparency film?

-- Jennifer Waak (jen.waak@visi.com), July 16, 2001.

In general I find the Polacolor Type 59 to be about 1/2 stop faster than any ISO 100 color transparency film. And Polacolor is lousy foir exposures that require reciprocity time corrections.

try this too but it might be a moot point since you are not synced to the shutter but assuming you have a pretty solid camera sitting on a pretty solid tripod & head you might try doing . Instead of leaving the shutter open for long periods, do a series of short exposures, the # in the series obviously linked to the number of pops you need. Since you are not sync'd , try doing a series of 1 sec exposures during which you fire the flash by hand. TYes you'll have to recock the shutter between exposures but assuming you don't kick the tripod this should work and you'll also cut out any low level ambient light from being recorded.

-- Ellis Vener Photography (evphoto@heartstone.com), July 16, 2001.

I actually am synched, or can be. I have synch cables, which work great for the first pop, but I have to unhook them for subsequent pops (on the same exposure). I have an Arca-Swiss Discovery sitting on some monster of a Gitzo tripod (I can't remember which one right now) and an Arca-Swiss B2 ballhead, so I'd consider it pretty darn sturdy. I'll try these exposures with the 5 and 10 pops using 5 and 10 exposures and report back this evening. Being synched should get rid of my reciprocity failure problem and help my exposures presuming I'm coordinated enough not to kick the tripod while recocking the shutter. :-)

-- Jennifer Waak (jen.waak@visi.com), July 16, 2001.

Jen, You might want to make yourself a cable that trips your flash. If your flash has a "household" plug, Home Depot and Radio Shack have the stuff you need... an electrical plug (2 prong), some lightweight electrical cable (the kind you would get to replace the wiring in a lamp) and a push button. Mount the push button in a Kodak film cannister, solder the wire carefully and connect your plug. Make it about 5'. I have a 5' one and a 15' one because I used to shoot big set stuff and had to walk around and meter... the longer one will come in handy. If your flash doesn't have a household plug, you can cannibalize a long synch cord.

-- Scott Walton (f64sw@hotmail.com), July 16, 2001.

As promised I did another set of exposures tonight using the bounce flash. This time I did multiple exposures on a single sheet of film rather than leaving the shutter open to avoid reciprocity failure; I set the shutter speed to 1/125. I also took my bellows factor into account this time as well. What I have concluded is that I think my light meter is about one stop too slow under low-light conditions. I metered the ambient light and got f2 at 1 second. I then metered with my flash and got f16. I took a Polaroid, and one pop distinctly underexposed it. 2 pops looked pretty good. I repeated this exercise at f22 (this time with 5 pops -- doubling the 2 to get to 4 and adding one for every 4 pops, per Ellis). f22 also looked pretty good.

This has been a tremendous learning experience for me -- thanks to everyone who has replied.

Now that I have my exposure problem solved I promise to go back tomorrow night and take one good photo of my subject ("good" being a relative term here), scan it in, and post it.

-- Jennifer Waak (jen.waak@visi.com), July 17, 2001.

Jennifer, I'd trust the Sekonic more than Polacolor in this case ....if you really want to nail down what's going on, try shooting some CTs, and do a ringaround test, maybe throw in a gray card, a white, and a black object, and maybe some type of metallic object to get a specular highlight. Have your film run by a Q-Lab, or someplace that's in control. Either that, or do it on b&w, same way, run it through your process, and make contacts at base +fog....to nail down your film speed...

-- DK Thompson (kthompson@moh.dcr.state.nc.us), July 17, 2001.

> I have synch cables, which work great for the first pop, but I have to unhook them for subsequent pops (on the same exposure).

Jennifer,

I am getting into this discussion late in the game, but I wanted to address your statement. If this is regarding your 550EX locking up after the first exposure, it is most likely due to shorting out the pins on the bottom of the flash shoe. you need to isolate these from the grounding plate of your flash-shoe adapter. I use a piece of mylar, making a mask around the central pin, and can multiple pop my 550EX's all day without problems.

-- daniel taylor (lightsmythe@agalis.net), July 17, 2001.

Jennifer you should have given me a call kevin

-- Kevin Kolosky (kjkolosky@kjkolosky.com), July 17, 2001.