Paul C. Buff, Inc. Technical Forum

Hello!

I'm now the proud owner of 2 x 86" Extreme Silver PLMs!
So far, I'm loving the gorgeous soft light for portraits, especially close in with the front diffusion material fitted..

However, I'm looking for some advice on focussing the PLM to get as concentrated a shaft of light as possible. I'm using the PLMs with T-One (Godox) QT600s mounted using the umbrella hole in the flash body. The 8mm umbrella mount is approximately 2" offset from the centre of the circular flash tube.
I've seem images taken using the 86" PLM on to a bare wall and these show the tightly focussed beam with a rapid falloff of light outside of the beam. This is what I'm looking to achieve for dramatic dance portraits (similar to the Damian Tierney & SharkCookie etc style).

I started by mounting the light & PLM on a light stand so that the front face is vertical and aiming it at a wall about 10' away & positioning the shaft so that the flash tube is just inside the front face of the umbrella. With a tripod mounted camera, I've tried taking multiple images whilst moving the umbrella shaft in and out from this position in approximately 1cm increments & looking for a change in the light pattern on the wall. There is some discernible movement of the bright centre area of the light projected by the PLM but there is still a huge amount of spill light bouncing around the room & the beam is no where near as concentrated as I'd hoped for.

In the light (sorry for the pun! :D ) of this info:
- Is there any better way of finding the optimal focus position for the PLM?
- Would the fact that I'm trying to do this test in my garage which is relatively small cause problems with spill light being reflected around the walls.
- Is the 2" umbrella mount offset causing this issue?
- I've not used the modelling light in a dark room to do the focussing as the front end of the modelling light is about 2" forward of the flash tube so I assumed that this would not give a correct position - Is this assumption correct?
- Is there any other advice anyone can offer?

Many thanks & best regards
Ian

I don't think moving the PLM a couple of inches is going to make that much difference. Maybe a foot, but two inches seems unlikely.

To control the spill, you could get some 4x8 foot sheets of foam core board in black from an artists supply (Get the black on one side and white on the other for versatility) and concentrate the light much like some huge barndoors to control spill. A big three-sided foam core house should do it and just move the whole PLM within it to focus and control the spill. Hope you got room though, or get a smaller PLM and stack them on a pole in synch like a strip light with smaller baffles.

I've got some black cine foil in a wide roll that might work as a clip on barndoor with clothespins to the arm ends of the PLM but never tried it. Mine is the 86" white one that serves as a shoot through or reflected, or even a outdoor sunshade screen). Also have the black and silver rear elastic cover that makes it more like a huge softbox since it attaches on the backside as a shoot-through, but spill would still be an issue without some way to channel the light via the foam core panels or maybe foil baffle.

Mack

I dont think you are going to see a spot light type of beam, you are going to have to filter out the spill light with a tight aperture or maybe ND filter. If you look at the samples on the PLM page that shows the type of spot I think you are looking for they shot at f32. I am sure to the eye, or a more open aperture it will not look this way. I would think you are going to need to move them way back, 15-20' use a smaller PLM or maybe the Omni is a better choice.

Many thanks for your thoughts guys!

I'd not noticed the aperture on the test images on the PLM page & my test shots were at either f/11 or f/14. I'll give it another go and close down the aperture... this does make sense as there was definitely a noticeable spot to some of my test shots where I was obviously close to the optimal focus, it just wasn't as defined as I'd hoped for, but I think a smaller aperture would help. I also need to get into the dance studio (which is much bigger than my tiny garage!) and use them in a more realistic setting.

I was thinking that movement of +/- 2" would make a reasonable change the exit light pattern due to the nature of the PLM. If all else fails I'll be making large barn doors!

Just for info... I'm pretty sure that what I'm looking is possible from these sources:
https://www.youtube.com/watch?v=W6bS8tgjSTw
http://www.peddecordphoto.com/2011/06/01/86-silver-plm/

And I'm thinking that angle the PLMs slightly forwards so that the rear edge of the beam is defined and I can burn the front portions in PP.

Thanks again for you help - It's much appreciated!

The optimal light position varies somewhat with the distance from PLM to subject. For indoor shooting at 7' to 20' distances, optimum focus is achieved with the flashtube pulled back from the edge periphery of the the PLM about 2-3".

I use the modeling lamp pattern and slide the PLM in/out to visually focus, then slide the PLM such that the flashtube is in the position the model lamp was in when I visually focused.

Also, particularly with the 8mm straight shaft, the PLM will sag a bit, so tilting the light/PLM up or down will visually place the beam center where you want it on the subject. This can be pretty critical, but can produce the same results with 8mm straight shaft as with the speed ring. I find the straight shaft version a lot easier to setup.

Many thanks Luap, I hugely appreciate the first hand info!

I'll have a go at some more test shots and have a play with the modelling light!
I didn't realise (but should have) that the subject distance from the PLM would make any difference so will definitely bear this in mind when trying test shots & when using in a larger studio.
I originally thought that I'd determine a set distance to position the PLM shaft and then use this every time I used the PLMs but will make a point of altering it depending upon how I'm using it.

Thanks again!

Paul, with the 8mm version of the PLMs, is the 8mm shaft removable in the same way that the 7mm shaft of the Buff speedring version is?

Apologies for hijacking the thread a bit.

No. The 8mm version has a fixed double wall shaft that is very similar to how a regular umbrella is constructed.

Thanks for that.

I always use the 8mm straight shaft - even with Extreme Silver. A lot easier to set up and cheaper.

You have to aim the Extreme Silver carefully with either mount. The slightly off center positioning doesn't effect the output pattern or coverage to speak of.