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Old April 30th, 2007, 05:06 PM   #1
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Confused about diffusion

I have read everything I can find (which isn't much) about using diffusion, and I have run tests of the various kinds (like Hampshire, Opal, Frost, Grid Cloth, and Spun) with my DV camera. As far as I can see, there is no difference in the image. I understand the value of diffusion in film, but is this also true in the case of video? Is anyone using it in video, to soften the image? Is there a handy reference that shows specifically what function each type is best suited for (beyond the Lee and Rosco websites)?

Thanks.
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Old April 30th, 2007, 06:05 PM   #2
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Try experimenting with the distance your light is placed from the subject. Diffusion filters have greater effect if they're placed closer, since they work by increasing the area of the light source. If a light with diffusion is placed too far away the area change relative to a clean hard light mightn't be that great.

Some filters like the Hampshire are subtle in their effect.
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Old April 30th, 2007, 06:14 PM   #3
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guessing - i would say that 90percent of users are using some type of diffusion on lights for video ...

i find video itself a little harsh - then add hard light ( ouch- for my taste) ) ...you might start with comparing opal to a full spun or grid cloth ( 1/4 spun/grid will be closer to opal) .... notice the shadow lines ( heavier diffusion will have softer lines ) ... at first it might be hard to see difference between all the diffusions and allot will come down to Dp's personal taste. i prefer spun ( over grid) , somebody else loves grid, and many love silks (synthetic and real silk...and then there are the lovely black silks ..real - forget black synthethic) ...

you'll have to do TEST to see which you prefer ... i prefer to do my test with persons face ....

i'm over in berkeley ... next time i do a lighting test i'll email you ...
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Old April 30th, 2007, 06:28 PM   #4
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It makes a dramatic difference in DV, especially when lighting people. I seldom use light on people's faces without some sort of diffusion (even if it's just on the barn doors). I will admit that the effect of very light diffusion like opal or hampshire is quite subtle, but diffusion is important as it gives you a way to control the quality of the light. Most of the good lighting books have a section on diffusion material. It can be a little daunting at first due to the sheer number of options, but it is well worth the time to understand the topic. If you're just starting, you can probably get along with a full diffusion (like Lee 216), a medium diffusion (like Lee 250), a light diffusion (like Opal), and a silk.
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Old April 30th, 2007, 08:21 PM   #5
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The key point made here is was what Brian mentioned: the size of the diffusion. The reason Rich doesn't see any difference between diffusion gels is that they are all probably no larger than 12"x12" and several feet away from the subject. Put a 2'x2' gel a couple of feet from the subject and you will see a dramatic difference. The SIZE of the diffusion is more important than the material unless the material doesn't diffuse enough to knock down the hot spot of the light. You need to spread the source of light out. This is what softboxes and umbrellas do to a light. You can put a big piece of diffusion on a frame and aim your light through it at your talent. Make a the beam from your light almost completely cover your diffusion. You will probably need to move the light back from the diffusion a couple of feet.
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Old May 1st, 2007, 12:02 AM   #6
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If for some reason you are stuck putting your diffusion material close to the light and aren't getting the desired effect you can stack another diffusion material in front of the first. Just make sure you have at least a little room between the two materials. I used to find this helpful when clamping 12"x12" gels in front of Home Depot lights...
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Old May 1st, 2007, 01:18 AM   #7
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Quote:
Originally Posted by Rich Wells View Post
Is anyone using it in video, to soften the image?
Absolutely. Softboxes are very common now in video production. Conventional lighting wisdom is that women should be photographed in soft light and this is a common practice in film and video too.

Fluorescent lights are in use more every day as a substitute for the softbox because it's soft by its very nature--can't really make it hard if you try.

With HD coming online in more use everday, soft light will be more important than ever. HD has a tendency to show up imperfect things like skin complexion imperfections, set details not as finished as they should be, etc. that weren't so obvious before with SD as we've known it all these years.
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Old May 1st, 2007, 07:00 AM   #8
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Just a thought - but I wonder if he meant diffusion on the camera? It gives a very different effect, but just as legitimate.

Rich - is that what you meant?
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Old May 1st, 2007, 11:16 AM   #9
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"Hampshire, Opal, Frost, Grid Cloth, and Spun"

those are diffusion for lights .. if you put them in front of lens you would be looking at white ( hampshire you could see thru it ) ...
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Old May 1st, 2007, 06:16 PM   #10
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Okay, so maybe you can tell I'm new to this lark. What threw me was the way he said 'Is anyone using it in video, to soften the image?' because you can use diffused lights and still get a sharp, contrasty image if you want.

I come from a photography standpoint and understand that 'soft light' can be very appealing, particularly in portrait stuff. But soft light doesn't equal 'soft image' I don't think. In some ways you can get a 'softer image' by using harsher lights but diffusion on the lens (or digital) - getting a 'dreamy' look.

I've still got a lot of terminology to learn it looks like!
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Old May 1st, 2007, 06:43 PM   #11
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Some of the lighter types of diffusion are more useful for theatrical lighting. In this application the lights might be 30 or more feet (10 meters) away from the stage, and the goal is to soften the edge of the light beam as opposed to creating a "soft light" for video. We do this all the time with followspots to make them blend in subtly with the stage lights, and also to soften the hard edge of instruments like ellipsoidal reflector spotlights such as the Source 4.

In these examples you would still have a point source light which casts hard shadows because of its distance from the subject, but it helps blend the individual lights together for a more subtle theatrical effect.
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Old May 1st, 2007, 07:00 PM   #12
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Quote:
Originally Posted by Simon Dean View Post
But soft light doesn't equal 'soft image' I don't think. In some ways you can get a 'softer image' by using harsher lights but diffusion on the lens (or digital) - getting a 'dreamy' look.

I've still got a lot of terminology to learn it looks like!

What you're talking about there is the old vaseline on the lens trick. There's other filters which duplicate the same thing though without the mess. Useful for making stars look better than they really are ;-)

That's definitely a different effect than using a soft, diffused light which is all the same very flattering for many subjects.
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Old May 2nd, 2007, 11:06 AM   #13
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So it helps to move it closer to the subject? Funny, in all the pictures I have seen of setups on the web and what I've seen on actual film shoots, I have never seen a gel put on a separate stand, close to the subject. It is always attached to the barn doors (which, as I said, does not seem to make any difference).

Nevertheless, what gels do you use? Sounds like Hampshire and Opal are very subtle.

Thanks.
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Old May 2nd, 2007, 06:35 PM   #14
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Here are some frames used to mount diffusion. http://www.chimeralighting.com/produ...m?productid=24

However, you can make your own diffusion frames from wood or you can also use metal flag frames, just remove the black fabric and clip on the diffusion.

Ralph's suggestion for a starting pack sounds fine.

BTW Usually, you need flags to control your soft light.
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