Paul C. Buff, Inc. Technical Forum

Technical Discussion Forum for all Paul C. Buff, Inc. Products

Login | Register

Post a reply
 [ 24 posts ] 

Fri Feb 25, 2011 11:16 pm

Joined: Sat Dec 12, 2009 3:29 pm
Posts: 15

kenyee wrote:
amplexis wrote:
has anybody tried adapting the 47" octobox grid to a PLM?


I'm fairly sure the 47" octa has less surface area than the 86" PLM....


i was thinking on the 51" just to see what the light was like. then maybe drop $200 for a 7' Photoflex octa grid on the 86" if the results are pleasing.




Top Top
Profile
 

#

Tue Mar 01, 2011 10:31 am

Site Admin
Joined: Tue Dec 08, 2009 10:43 am
Posts: 4596

Keep in mind the 86" measurement is across the arc, not the face. Remember too, you will have to cut a hole in the middle of the grid for the light head.



_________________
TS
info@paulcbuff.com
1-800-443-5542


Top Top
Profile
 

#

Tue Mar 01, 2011 8:37 pm

Joined: Fri Dec 18, 2009 11:50 am
Posts: 306

Technical Support wrote:
Keep in mind the 86" measurement is across the arc, not the face. Remember too, you will have to cut a hole in the middle of the grid for the light head.


If you have a few moments at the factory, could you see if the biggest PCB 47" octa grid fits over the 64" PLM? I think it'd fit if you can make some sort of sock out of lycra fabric on the outer rim...




Top Top
Profile
 

#

Sat Mar 05, 2011 1:44 pm

Joined: Thu Jan 07, 2010 2:46 pm
Posts: 53

PLMs seem to follow Wisniewski's first law of umbrellas, the face diameter is about 85% of the bow measurement, 72 inches for the 86 inch PLM, 51 inches for the 61 inch PLM.

I tried doing a goniometer scan on PLM fabric, and got about a 17 degree spread. So, it's pattern is a lot like light that's collimated, then spread an additional 17 degrees. A gridded box produces the same effect, except it starts with light coming from every point at a huge 100-160 degree spread, then "choked" to a whatever the grid's spread is. The PLM 72 inch PLM is virtually identical to a 7 foot octa with a 6 foot round mask and a 20 degree grid. (which you can set up using Chimera stuff, for about $1000, LOL).

If there were some way (hint, hint, Buff people) to increase the spread of the PLM fabric to 40 degrees, it would be identical to a box choked to 40 degrees. Increasing the "bumpiness" of the silver reflector would do it, but that would be a permanent fix.




Top Top
Profile
 

#

Sat Mar 05, 2011 1:52 pm

Joined: Thu Jan 07, 2010 2:46 pm
Posts: 53

Luap wrote:
Any modifier with diffusion fabric (softbox, white umbrella, etc) will have a very broad falloff - typically around 150°. The same applies to a white beauty dish.

Silver PLMs have a very focused output, with sharp falloff outside the main pattern, But because of it's size, the main pattern is quite wide in terms of area actually lit. When the white front diffuser is added to PLM it's angle of coverage is vastly increased and is similar to a softbox.


I have noticed that pretty much every soft box and light modifier uses that heavy a diffusion material. But there are materials with a lot less than 150 degrees of scatter.

How about a very sheer diffusion fabric?

Or maybe a pebble textured plastic sheet.

I use textured plastic with a much lower scatter, about 40 degrees, for a lot of my macro lighting and the little softboxes that I make for product photography. I also have a diffuser sock made (believe it or not) from a textured plastic shower curtain that I use on my beauty dish, that adds another 20-30 degrees (I've never bothered to set that one up on the goniometer).

Or, if Paul were to offer a reasonably priced grid for the 86 inch PLM, this would sort of be academic.




Top Top
Profile
 

#

Sat Mar 05, 2011 3:26 pm

Joined: Thu Jul 01, 2010 10:58 pm
Posts: 213

I don't understand why we would want the straight, unmodified silver PLM to act like a soft box. It's value and purpose is to act like a PLM, not a big soft box.

Don't the white PLM, and or the white diffusing cover give you the softbox look you want?

The real comparison to make is the PCB PLM against the other parabolics on the market: the price difference is measured in thousands of dollars.

And you can (as I have when it suited the shot) put the white cover on, have a six foot diameter soft box.

Since the intent of a silver PLM is the collimated light, why would we want the silver adjusted to be less so?

I must be missing something in your post, I guess.




Top Top
Profile
 
Website
 

#

Sat Mar 05, 2011 4:28 pm

Joined: Thu Jan 07, 2010 2:46 pm
Posts: 53

BDP, there's people who would like it to act like, well, anything and everything. It's cheap, and big, and that makes a great "foundation". That's why Paul has a sock for it, so you can switch it from the original 18 degree (more or less) collimation to 150 degree. It's also why he (like all soft box makers) has grids for his soft boxes and octas, so they can go from that 150 degree collimation to 40 degrees.

Chimera is so "gung ho" about that, that they sell 20, 30, 40, and 60 degree grids for their soft boxes.

But there are limits to that approach. A conventional soft box isn't that good a collimator. I've used some of mine without the front diffusion panel, and they're uneven and poorly focused. So, the only way to get narrow patterns out of them is to overdo the diffusing (those conventional 150 degree diffusers that Paul mentioned) then gird the light aggressively. That eats a ton of light. About 5 stops for a 20 degree grid over a diffuser panel. The PLM has virtually that identical pattern, it's really similar to a big box with a 20 degree grid, but 5 stops more powerful. Even close up, in a studio, that's useful. It's more power than you need to take the picture, but it helps you compose the picture. The more aggressively you modify a light, the more you need to be able to see what you've done, via modeling lights. Put a 5 stop modifier on a monolight with a 300W halogen modeling light, and you've got a whopping 10W of light to compose by.

A diffuser that doesn't scatter much light, one that just adds another 20 degrees to the 18 degree spread of a PLM, would match the 40 degree gridded box, with over 4 stops more power, and radically less cost.

Cost is a key. It's hard to appreciate how really big a PLM is. The 86 inch has about 29 ft2 of front area. My Chimera 6 foot Super Pro Plus has 27 ft2, and I think the nearly round PLM makes for more natural shadows. So, the $103 PLM can do the work of two 6 foot soft-box configurations, no grid and 20 degree grid (and that's a $1,300 configuration for the Chimera: you're talking $500 for the 6 ft box and $800 for the 6 ft 20 degree grid). The 20 degree Chimera grid weighs a ton, it strains (and warps) the box and whatever it's mounted on. The 20 degree configuration of the PLM means just taking the sock off.

I'd gladly pay $50 each for diffusers that could bump that up to matching the 40 and 60 degree Chimera grids. Heck, complete PLMs weigh less than Chimera 6 foot grids, it might be worth experimenting, spraying matte clear lacquer on a silver PLM to see if I can increase the scatter of the reflector to 40 degrees. Although I still see a lot of promise in my earlier idea about playing with diffuser material.

And an added bonus feature, PLMs focus a bit. You can't do that with a soft box. Slap on a 40 degree "silk", focus the PLM in to 6 feet, what you could do with that for product photography. It's mind boggling.




Top Top
Profile
 

#

Sat Mar 05, 2011 5:51 pm

Joined: Thu Jul 01, 2010 10:58 pm
Posts: 213

Joseph S. Wisniewski wrote:
BDP, there's people who would like it to act like, well, anything and everything. It's cheap, and big, and that makes a great "foundation". That's why Paul has a sock for it, so you can switch it from the original 18 degree (more or less) collimation to 150 degree. It's also why he (like all soft box makers) has grids for his soft boxes and octas, so they can go from that 150 degree collimation to 40 degrees.

Chimera is so "gung ho" about that, that they sell 20, 30, 40, and 60 degree grids for their soft boxes.

But there are limits to that approach. A conventional soft box isn't that good a collimator. I've used some of mine without the front diffusion panel, and they're uneven and poorly focused. So, the only way to get narrow patterns out of them is to overdo the diffusing (those conventional 150 degree diffusers that Paul mentioned) then gird the light aggressively. That eats a ton of light. About 5 stops for a 20 degree grid over a diffuser panel. The PLM has virtually that identical pattern, it's really similar to a big box with a 20 degree grid, but 5 stops more powerful. Even close up, in a studio, that's useful. It's more power than you need to take the picture, but it helps you compose the picture. The more aggressively you modify a light, the more you need to be able to see what you've done, via modeling lights. Put a 5 stop modifier on a monolight with a 300W halogen modeling light, and you've got a whopping 10W of light to compose by.

A diffuser that doesn't scatter much light, one that just adds another 20 degrees to the 18 degree spread of a PLM, would match the 40 degree gridded box, with over 4 stops more power, and radically less cost.

Cost is a key. It's hard to appreciate how really big a PLM is. The 86 inch has about 29 ft2 of front area. My Chimera 6 foot Super Pro Plus has 27 ft2, and I think the nearly round PLM makes for more natural shadows. So, the $103 PLM can do the work of two 6 foot soft-box configurations, no grid and 20 degree grid (and that's a $1,300 configuration for the Chimera: you're talking $500 for the 6 ft box and $800 for the 6 ft 20 degree grid). The 20 degree Chimera grid weighs a ton, it strains (and warps) the box and whatever it's mounted on. The 20 degree configuration of the PLM means just taking the sock off.

I'd gladly pay $50 each for diffusers that could bump that up to matching the 40 and 60 degree Chimera grids. Heck, complete PLMs weigh less than Chimera 6 foot grids, it might be worth experimenting, spraying matte clear lacquer on a silver PLM to see if I can increase the scatter of the reflector to 40 degrees. Although I still see a lot of promise in my earlier idea about playing with diffuser material.

And an added bonus feature, PLMs focus a bit. You can't do that with a soft box. Slap on a 40 degree "silk", focus the PLM in to 6 feet, what you could do with that for product photography. It's mind boggling.


Yea, I get that, and additional modifiers, grids, etc. are fine (and welcome). My main question was about your suggestion to change the silver in the PLM itself, to make it more diffuse. I would object to that, since I value the more focused, collimated light of the bare silver PLM. Anything you want to do, or anything PCB wants to do, in terms of more add-on modifiers, I am way cool with. Just don't go making the spread on the bare silver PLM wider. That's all, and that's the only thing I didn't "get" from your earlier post.




Top Top
Profile
 
Website
 

#

Sun Mar 06, 2011 8:15 am

Site Admin
Joined: Tue Dec 08, 2009 10:43 am
Posts: 4596

Per conversations with Paul, the PLM can focus (with even coverage) from about 15-25d. The positioning umbrella screw can be loosened an the reflector can be moved in or out for different focusing, tightening the screw for a friction fit on the positioning shaft.



_________________
TS
info@paulcbuff.com
1-800-443-5542


Top Top
Profile
 

#

Sun Mar 06, 2011 11:52 am

Joined: Thu Jan 07, 2010 2:46 pm
Posts: 53

BDP wrote:
Yea, I get that, and additional modifiers, grids, etc. are fine (and welcome). My main question was about your suggestion to change the silver in the PLM itself, to make it more diffuse. I would object to that, since I value the more focused, collimated light of the bare silver PLM. Anything you want to do, or anything PCB wants to do, in terms of more add-on modifiers, I am way cool with. Just don't go making the spread on the bare silver PLM wider. That's all, and that's the only thing I didn't "get" from your earlier post.


OK, then it was just a misunderstanding. I don't want the original PLM changed, that narrow, precise beam is just too useful. I was thinking about a additional item for the range.

Personally, my favored approach is add-on diffusers for the PLM, a +20 degree silk and a +40 degree, to take the 18 degree (which is close enough to 20 degrees) PLM and "kick" it up to 40 degrees and 60 degrees.




Top Top
Profile
 
Display posts from previous:  Sort by  
Post a reply
 [ 24 posts ] 

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: Bing [Bot] and 3 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum


Search for:
Jump to: