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Old February 20th, 2004, 04:11 PM   #1
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dual polarizers and ultra contrast

can someone remind me how to use the dual polarizers for a variable ND filter? Does this reliably work?

I've had some success using an ultra contrast filter and playing around with contrast/color levels in post in adobe premiere. some great looking footage. anyone else using this filter?
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Old February 21st, 2004, 03:13 AM   #2
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To answer a question with a question: how do you like the ultracon? Does it give you an advantage over what you could produce from post work alone?
Ken
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Old February 21st, 2004, 08:41 AM   #3
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Ken: yes, Josef, try doing a search under "ultra con". We've discussed this filter at length in the past.
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Old February 21st, 2004, 10:10 AM   #4
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Sure. This post used to be in the HD-10 forum. I was simply asking his personal experience.
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Old February 21st, 2004, 05:42 PM   #5
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some people say you lose resolution with the ultra contrast filter, but i haven't seen that to be the case. Some of the stuff i shot in a deli here looks gorgeous with the HD10u. I used a #3 ultra contrast filter with a 0.9ND filter to control the aperature. In post, i took the contrast up 10%, the brightness down 10%, the luma preserve up 100%.

In premiere (and Aspect) you can play with the 3 colors (RGB) colors at three different levels - shadows, mids and highlights. I basically upped all 3 colors of the shadows and highlights from 0 to 100 and left the mids as they were. I imagine i'm changing the gamma or something, but i'm really just experimenting. Of course, the ND filter forces the aperature wide open giving a beautiful film look, especially long shots using the zoom and close-ups of the food, etc.

my $0.02

Still wondering if how people are using the two circular polarizers to get a variable ND filter...
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Old February 21st, 2004, 09:05 PM   #6
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Why did this post get moved? We are talking HD-10 shooting techniques.
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Old February 21st, 2004, 10:09 PM   #7
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I don't see anything specific about the HD-10. The questions and responses are fairly general in nature and could apply to many cameras. The technique of using 2 pols as a variable ND is applicable to any camera.
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Old February 22nd, 2004, 09:18 AM   #8
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Just to clarify: I try to use proper punctuation and reasonably decent grammar when posting so that misunderstandings don't happen, but it looks like I failed on this one. My first response should have read:

Ken--Yes, it does give an advantage.

Josef--To see other's notes here on the ultracons, try doing a search (etc).

Sorry for the misdirection.
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Old February 22nd, 2004, 10:06 AM   #9
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The use of two polarizers to achieve variable ND is problematic at best. You can not use two circular polarizers, it won't work. You can use two linear polarizers. You can use one linear polarizer and one circular polarizer, but the circular must be attached to the lens first, then the linear.

The polarizers must be absolutely neutral in color or else odd colors may result. I would stick to either B + W or Heliopan because of their high quality standards and neutral color. I would not mix brands.

Vignetting may occur because the polarizers must be stacked. The thin mount polarizers can't be used because they do not have outer threads to attach the second polarizer. One regular and one thin could be used if mounted correctly.

Image quality may suffer. Stacking filters introduces two additional elements (four surfaces) to the optical path. The amount of image degradation will be dependant on the quality of the filters. Again, pick the best to minimize unwanted effects.

Compare the cost of two high quality polarizers to a set of ND filters. It may be more cost effective to go the ND filter route. Although, carrying just two polarizers could reduce space and size required in your bag. If you experiment with this please post your results. Good luck.
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Old February 22nd, 2004, 12:35 PM   #10
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Joseph - May I ask which brand of ultracon you went with? As well, any change to you shooting technique when using the ultracon? I mean do you back off on under exposing or anything different that you would normally do when shooting with the HD-10?
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Old February 22nd, 2004, 08:28 PM   #11
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ken

i'm fairly new to using the HD10u, so there isn't ANYTHING that I do "normally.

I use 58mm Tiffen #3 ultra contrast filter with a B&W brass step up ring. Fifty eight mm helps with stacking filters and i needed 58mm anyway for my century optics wide angle lense. BTW, the filters work fine BETWEEN the camera and the wide angle lense - saves me from having to buy two sets of filters.

i'm just experimenting with the ND filters (also Tiffen). For the deli shot i did, 0.6 was too little and 0.9 was just right. As with others, seems the idea is to add ND filters until the aperature is locked wide open and doesn't change when going to darker areas in the scene.
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Old February 22nd, 2004, 10:46 PM   #12
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How would you manage to arrange a "dual polarizer, one rotating" with your setup? Or would you have to move to a rotatable slot matte box?
Ken
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Old February 23rd, 2004, 11:07 PM   #13
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Ken:

Ultracons are patented by Tiffen, not a generic type of filter like a polarizer that is manufacturered by multiple companies.

For me, using an Ultracon means you can generally stop down a bit more without the shadows blocking up, which results in a slightly greater latitude (i.e. lowering shooting contrast).
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Old February 23rd, 2004, 11:41 PM   #14
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Yes I understand that. I am considering almost the exact same setup as what is bing described here. What I am trying to figure out is how to get all of it to work together. I would like to use a Ultracon and a wide angle lens. As well of course the two polarizers that would serve two purposes, polarizer and variable ND filter.
Is there a way to make all this work together?
Is a matte box in this case, absolutely necessary?
Will a matte box work with the Ultracon and wide angle lens?

Our purchase of this cam is being held up because of the lower price in the States, but comes with a matte box in Canada, but costs a lot. Can anyone set me straight on what I will need to make it all work?
Thanx
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Old February 24th, 2004, 08:45 AM   #15
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My recommendation is that if you are considering Ultracons, you should be using a mattebox. If a light source strikes the face of this filter, it can flare out the image overall to a varying degree. A good mattebox with an eyebrow and side flaps will go a long way to help this. Ultracons are a bit high maintenance as far as filters are concerned; they do need that protection from extraneous light and they will shift their effect when the camera is panned through scenes of varying contrast. I've used them and loved them, and I've also had problems come up with them and wished I'd left them off.

Here's a film that I made using Ultracons for certain shots (scroll down to Instant Fillms 009, film called "The Girl's Guide to Summer"). Because of the very strong sun which I generally shot backlit, I needed to open up the shadow areas in places. The scene in which the female character in the bikini (see, now I've got your curiousity!) is modeling for the other two had some very dark foliage in the background, and I wanted to bring the ratios closer. I achieved this to a certain degree, but it did cause some sky flare due to the characteristic of the Ultracons. The whole film was treated to give it an early 60's color palette.

After color correction, I felt I might have been just as successful or more if I had not used the Ultracon and brought up the foliage in post.
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