CROSS POLARIZATION with flashes and umbrellas !!!

[docholliday]

I note these very interesting remarks, thank you Docholliday!
By reading you, I notice that, compared to Profoto D2 flashes, the use of Hedler LED 1000 constant lights does not present any disadvantage in terms of colorimetric rendering.
This added to the practical side of constant lighting, I'm thinking of using Hedlers with cross polarization for small and medium formats, and perhaps reserve flashes for large unvarnished formats, not being able to polarize the lighting with umbrellas.
I don't really know what to do for large formats (approximately 1.5 x 2.5 meters) varnished... Hedlers cross polarized from further away perhaps, to be tested...

Some LED lights can have a very narrow spectrum, and reduce color rendition of subjects especially if they have very out of gamut colors.

I tend to always use flash as it prevents any vibration or room lights from affecting renderings. It's also easier to get the power you need with flash.

The trick to cross polarization with large paintings? Very far back from the subject, NO diffractive/reflective modifiers. Any scrim, umbrella, or softbox will difuse the light - which makes the light come from all directions, losing polarization. If you have enough power, you can just put a roll of polarizing film in front of your softbox, but then you are defeating the purpose of the softbox.

So, I usually hang the large subjects on a wall painted neutral grey with a floor also painted in the same paint. Move the lights waaay far back, place a polarizing film in a filter frame in front of the lamps, polarize the lens and shoot away. The problem you may have is that you may not have enough power to do large imaging. I tend to use 4x 2400w/s heads to do large work. You can also turn off all lighting, lock the shutter open, and multi-pop smaller strobes to give the power you need. But, be careful, as again, some lights are not consistent enough between each shot and can change color temps on you.

Long exposure on hot/cold/LED lights may not work as well at times. Some camera sensors are more sensitive to certain colors than others. Long exposures may make some colors over saturated in order to get others exposed correctly. Think reciprocity failure in film - it can affect sensors in digital as well for critical applications. Also, long exposures in certain rooms can cause problems. Vibrations from HVAC or traffic driving outside can cause subtle loss of sharpness. There are times where the Hasselblad multi-shot cameras will stop/fail capture because of an AC unit kicking on or a truck driving down the street a few blocks over.

[ALAIN]

Thank you very much for all these "clarifications
So, that's for sure too: big picture => big studio!

[JCM-Photos]

Be also careful with SG type charts that sometimes can partially glare without noticing it.

The by glare impacted parches give then some totally false individual colors

[ALAIN]

I like the practical side of the Hedlers, in direct lighting with barndoors. I saw an accessory that allows you to mount a polarizer on the Hedler binding, but I couldn't find where to get it! Its only drawback seems to be not being able (without tinkering) to add barndoors. I indicate the link, if the forum knows where to find this wonder...

https://correlatedsolutions.eu/polarization-filter-for-hedler-led-2/

Hello,
I found where to get these filters mounted on a mechanism dedicated to Hedler Led 1000.
The Company has several in stock.
www.correlatedsolutions.eu
www.isi-sys.com
It is artisanal production in very small quantities. As a result, the price can be dissuasive: 390€ each!
The quality would be excellent, especially in terms of light reduction and heat resistance, which is still present with these high-power LEDs.
I ordered 400x400mm polarizing flexible filters, to be fixed on the barndoors, which cost me 8x less.
In addition, the "390€" system does not allow barndoors to be mounted in front. In my case, they make it possible not to water the whole room, even with the zoom of the Hedlers.
Thanks again for sharing your experiences.
(((You know: I invented cross-polarization in my head a few months ago, and then I realized, just after, that it has been practiced for a long time by a lot of photographers;) )))
See you soon
Alain

[NickT]

Also if you are doing a lot of this sort of work consider one of these:

http://www.zig-align.com

[ALAIN]

Thank you, good idea. For this moment, I use a mirror with a cross in the middle, in the middle of the painting : I have to see the center of the lens just on this cross

[JCM-Photos]

As I don't do it often, I make a geometrical drawing on the shooting site soil with measuring tape, a roll of thread, pencil and a plumb line, easy and precise but time consuming