Reflectors for intensifying strobe light

[-chrille-]

I am look for reflectors to intensify the light output when shooting collodion wet plate with strobes.

I have three Elinchrom strobes. All with a ”standard” reflector 160mm in diameter and 60 mm in depth.

I have done some tests and for a decent(highly subjective of course) exposed plate I need a f/16 reading at ISO 3 set on my Sekonic flash meter. With f/5.6 lens aperture. And it seems to be pretty consistent for high contrast/low key photos.

That means, using one strobe, must be no more than 400 mm away from the subject! Thats a bit impractical.

Are there any light shapers that can intensify the light output with about 2 stops? That would increase the distance from strobe-subject to 800mm, right?

What kind of reflector should I look for? Is bigger always better?

And of course for still life you can always fire the strobe multiple times.

 

[FotoD]

Wouldn't a fresnel be more efficient? Some claim a 2 LV increase of light in the centre. I doubt a standard reflector will give you that much.

 

[koraks]

Wouldn't a fresnel be more efficient?

I'd expect so, yes.

Are there any light shapers that can intensify the light output with about 2 stops?

No. You can't intensify light. You can try to bounce as much as possible into the direction of your subject. A standard strobe already does this reasonably well. I don't think a different parabolic reflector is going to make all that much of a difference. The light fans out pretty much immediately after leaving the reflector.

You could use a proper collimator combined with a reflector. Maybe you'll gain 2/3 of a stop.

If you make your light more directional and put it further away from your subject, the light will also be harsher. You may find this becomes u pleasant at a certain point, especially for portraits.

With collodion, you can muck about to the point where you draw the inevitable conclusion: you just need all the flash power you can reasonably get. Life starts at 800Ws or so. More is better.

 

[Pieter12]

When Chuck Close made daguerrotypes, he wanted to shorten the exposure time. Close and Jerry Spagnoli devised a strobe set-up that produced 30,000 watt-seconds of illumination, which is enough to make an instantaneous exposure. The level of light is so bright it can redden the sitter’s skin and even singe hair.

 

[Mal Paso]

There are lots of great deals on strobes now, especially high power as large film cameras retire. I'm up to 20,000 WS. LOL

Elinchrom must have a narrow angle reflector.

 

[-chrille-]

I bought the Elinchrom High Performance 48° 260mm reflector.

Compared to a 160mm reflector.

Here are some readings with Sekonic L-308X:

1 meter distance, ISO 3. Elinchrom RX 600 at maximum 600Ws.

Bare bulb f/6.3

Small reflector 160mm f/7.1

Large reflector 260mm f/16

 

[-chrille-]

That is more than 2 stops over the umbrella reflector!

With 3 600Ws strobes and the ”High Performance” reflectors I think it is possible to do some good exposure wet plates. But as Koraks stated above the light will be hard. I think really harsh. I have to experiment some.

 

[MattKing]

Correct me if I'm wrong, but with wet plate doesn't the spectral distribution of the flash light output and modifier combination also matter?

 

[-chrille-]

I am not sure but I think all strobe flash tubes are filled with xenon gas and should emit same spectral distribution. I have very little experience with flash photography and feel I am walking on thin ice here.

I am going to make some plates with a strobe and my new reflector and post the result.

I am impressed how much gain in light output the Elinchrom 260 mm reflector gives over the standard reflector.

 

[MattKing]

I am not sure but I think all strobe flash tubes are filled with xenon gas and should emit same spectral distribution.

Don't forget that there are materials between the tube and the subject - glass/plastic and anything that a reflector might be made of.

 

[BrianShaw]

Aren’t collodion wet plate orthochromatic, making strobe lighting and measuring with flash meters a real challenge?

 

[koraks]

Correct me if I'm wrong, but with wet plate doesn't the spectral distribution of the flash light output and modifier combination also matter?

Yes. Reflectors like these tend to bounce a lot of the short wavelengths, so they're generally a good choice (and definitely better than nothing).

Aren’t collodion wet plate orthochromatic

Blue/UV-sensitive, even. Not even orthochromatic. However, relative light measurements of the same light source under different conditions are still a pretty good indicator.
In the end of course you just have to shoot some plates to know whether it works. Fortunately it's fairly quick & easy to wipe a plate and to do a new one if it doesn't come out as expected.

 

[Mal Paso]

Later model strobes tend to have UV blocking coating on the flash tubes to prevent optically brightened fabrics from fluorescing but the spectral range is basically daylight.

 

[-chrille-]

I did a test plate with one Elinchrom 600RX strobe and the 260mm reflector I mentioned earlier in this thread.

This is one pop with the strobe. Distance 1 meter from subject. A Zeiss Triotar 150mm wide open at f/3.5 on a 5x7 plate.

I am surpriced that the strobe light of only 600ws was strong enough to give me that bright exposure! The highlights developed in a couple of seconds when pouring the developer on plate.

And as you can see the light is really harsh with blown highlights and I think it is hard to control the highlights with a reflector and poor dynamic range of collodion, especially subjects with high reflective surfaces. I was using a black backdrop and my intention was making a completely black background but it reflected a bit of light.

I will try some more plates.

 

[koraks]

I am surpriced that the strobe light of only 600ws was strong enough to give me that bright exposure!

600Ws from 1m distance is a lot of light. I only ever had with 200Ws (two pcs) to work with. Based on what you show, I see no magic in the reflector, to be honest. It's about what I'd expect from a 600Ws unit with regular parabolic reflector at close distance.

And as you can see the light is really harsh with blown highlights

Well, yes. I also see lots of fog and oyster shells. Have you tried developing a little less? This is the usual way to control the highlights and it'll also reduce the fog. More exposure + less development = lower contrast. This works very well with collodion. Borut Peterlin published some videos about this a few years ago; they're very nice demonstrations of the principle at work in wet plate photography.
Getting rid of the oysters is a matter of more thoroughly cleaning the edges of the plate.

 

[-chrille-]

It is a reused aluminium plate and not in very good shape. Rinsed and used just for experimenting. I have a whole box of them, dont ask why

I will try reducing my developing time This was 12 sec. Is it actually fogging on the plate? If you mean all the light patches around the jar it is the reflections/highlights in the satin backdrop you see.

 

[koraks]

Is it actually fogging on the plate?

You made me look again; I stand corrected. The edges that were masked by the holder look clear. So it's really in-scene exposure. I think what's throwing you for a loop here is that satin may be black, it can (apparently does) still reflect UV. I.e. it may be blacker to our eyes than it looks to a collodion wet plate.
Having said that, your exposure sure is ample. Feel free to dial it back down if you find that you still have too much background after cutting back development time to reel in the highlights. It's a matter of taste, of course, but I think the scene would end up looking better if you actually allow the backdrop to show up; the texture is kind of nice...