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Can you still use a ND filter if your projector has a dynamic iris ?

post #1 of 36
Thread Starter 
Just wondering if you can still use a filter if your projector has a dynamic iris ? or are these filters best with projectors that dont have one?
post #2 of 36
It is fine either way, doesn't matter.
post #3 of 36
Thread Starter 
Ok thanks!! is ND2 filter the one to get to try and improve black level and dim brightness? I have a Optoma HD87 smile.gif

Slightly off topic but makes me wonder if using a filter on a Sony HW50ES could get it even closer in black level to the VW95 smile.gif
Edited by jamieuk147 - 10/5/13 at 3:21pm
post #4 of 36
Depends how much brightness you are trying to tame, but...

To see a decent amount of difference, the ND2 (0.3) is probably the minimum one you need (it will drop brightness by 50%, but this will only appear about 25% less bright to your eye). The ND4 (0.6) drops the brightness down to only 25% of what was originally there, and an ND6 (0.9) drops it to 12.5%, and so on and so on.

Putting on an ND4 filter is about the same as wearing 3D glasses, so it will drop the brightness too much for most peoples setups, so the ND2 is probably about right.

The common ones people buy in the forum are the Hoya ones, just make sure it is made of glass and not RESIN (plastic). They cost about $35 generally. There are variable ND filters that can be adjusted (or you can just buy 2 different ones), but I heard the variable ND's have some issue (not as good?), but I never tried one.
post #5 of 36
I use a B&W MRC nd2 filter on my LS-1 to tame the brightness a bit and it works like a charm.
post #6 of 36
I was using this ND filter on my PD8150. The lens barrel is threaded so this fit perfectly:

http://www.ebay.com/itm/190485409766?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649
post #7 of 36
There are much better quality ND filters than the brands listed here. Ideally, the ND filter should not be mounted (screwed in) parallel to the lens. I have a square high optical quality ND2 filter that I can swing in front of my lens with an arm and its mounted on a gooseneck to let me tilt it like a projection booth glass window. While the ND filter will lower your black reference level it does have some adverse impacts. To name one, it will lower the MTF of your system in the vacinity or 3%. We measured the reduction years ago but I don't remember the exact number. It was large enough for me to abandon the use of a ND filter.
Edited by mark haflich - 10/5/13 at 10:44pm
post #8 of 36
Mark... I understand why mounting an ND filter normal to the projection path could introduce reflections and reduce contrast, so why do high-end projection companies include threads on the lenses? Do you think multicoated B&W and the higher end Hoyas are poor, or are you just talking the mounting? I'm much pickier about optical imperfections on my photography than I am with movies, and the filters are definitely not the weakest link wink.gif
post #9 of 36
Never use a vari nd filter. It creates some kind of hue shift... it works by reversing some kind of opposing polarized glasses.
post #10 of 36
Thread Starter 
Being a huge DLP fan this filters can hopefully help the technology get a little closer to JVC and Sony in black level

Did you notice an improvement Seegs with your Planar? that would be one of the top DLP projectors I could think of to work with a filter
post #11 of 36
It seems like simply adjusting down the iris/brightness would be superior to using an ND filter. Closing the iris improves contrast by blocking more stray light and letting more good lithe through. The ND filter blocks everything at best and causes new problems at worst.
post #12 of 36
Thread Starter 
Would a grey screen be a better choice then in a light controlled room for a high lumens DLP then?
post #13 of 36
Quote:
Originally Posted by rcohen View Post

It seems like simply adjusting down the iris/brightness would be superior to using an ND filter. Closing the iris improves contrast by blocking more stray light and letting more good lithe through. The ND filter blocks everything at best and causes new problems at worst.
True, but with no manual iris adjustment, it may be the only choice in some cases.
post #14 of 36
I ordered the filter that Seegs was using to see how it looks on the 8130. It was inexpensive, so it's no big deal if it doesn't work out.
post #15 of 36
Quote:
Originally Posted by jamieuk147 View Post

Would a grey screen be a better choice then in a light controlled room for a high lumens DLP then?

Yes. But choose wisely.
post #16 of 36
Quote:
Originally Posted by jamieuk147 View Post

Would a grey screen be a better choice then in a light controlled room for a high lumens DLP then?
A larger screen would be an even better choice in most cases biggrin.gif
post #17 of 36
Quote:
Originally Posted by dougri View Post

Mark... I understand why mounting an ND filter normal to the projection path could introduce reflections and reduce contrast, so why do high-end projection companies include threads on the lenses? Do you think multicoated B&W and the higher end Hoyas are poor, or are you just talking the mounting? I'm much pickier about optical imperfections on my photography than I am with movies, and the filters are definitely not the weakest link wink.gif

No. The better ones are OK but with big buck projectors I didn't want to interject a filter below the quality of the lens. With projectors in the under $10K class I wouldn't worry too much. My filter is a Schneider, it cost between $100 and $200, was 3"x3" sq and was very very difficult to find involving multiple phone calls to Schneider. I gave up trying to get a 4"x4".

With hardly any exceptions, projector manufacturers buy rather than make their lenses.. Many more expensive projectors brands use the same lenses as their competitors. Cheaper projectors seem to use different lens each. Lens manufacturers use stock parts and since camera lenses all have groves for installing UV filters etc, its pretty standard to provide groves on projector lens. The groves won't affect performance at all and having the groves might result in a few more sales of the projector. However, I suspect very few projectors end up with a filter installed on the lens. And the vast majority are used to cameras and screw on filters normal to the light path but I think you can see the difference here. Its one thing to reflect light back to what you are shooting, most often a fairly large place vs reflecting back to the primary lens on the projector. We tend to be lazy, but if you are going the ND filter route, why not minimize adverse impacts by tilting the filter. It isn't hard to figure out something to hold the filter at an angle. Manufacturers ofter provide for extreme amounts of lens shift, it means more sales, but it doesn't mean you should use extreme amounts just because the manufacturer provided it.
post #18 of 36
I wouldn't recommend ND filters with the Sony line. You can program in the iris max and min, which gives you a great deal more flexibility than you get from an ND filter, and allows the use of smaller iris diameters for higher contrast.
post #19 of 36
The Sony lens on the 500/600 and the 1000/1100 are either made by or manufactured to Sony's unique design. I don't think the 1000ES even has groves but I have never looked. I definitely would not use a ND filter on the 1000/1100.
post #20 of 36
Quote:
Originally Posted by zombie10k View Post

I ordered the filter that Seegs was using to see how it looks on the 8130. It was inexpensive, so it's no big deal if it doesn't work out.

That is the ND filter Planar recommended people get. The picture overall loses a bit of pop but the black level does look better with it installed which is exactly why I bought it.
post #21 of 36
I've been wondering about getting one just to try, I mean, it's got to be the cheapest 'upgrade' you can do anyway.

but I am curious what you guys think is the best way to achieve darker blacks: grey screen, closing iris, ND filter, combo?

I currently have a .8gain grey screen and a jvc x35 projector. the projector is far too bright with the iris fully opened, and pretty decent if not a touch bright at -15(fully closed). talking of black levels only, I can clearly see my hand cast a shadow on a solid 'black' screen with the iris fully open. I can see the shadow at -15 after my eyes adjust. i'd love to get to the point of black actually being indistinguishable from ambient lighting hitting the screen(there isn't much). i'm assuming there wouldn't be a way to get to that point without sacrificing too much brightness, but i'd like to find that happy medium.

so, grey screen + iris fully closed isn't quite dark enough. do you think white screen + iris fully closed + ND filter, or, grey screen + iris slightly open + ND filter could possibly be any better?
post #22 of 36
I bought a cheaper ND2 filter with my Sony HW50ES and my thoughts are it's not worth the time. Like said if you don't angle the lens you'll see reflections. Then I saw a very slight improvement with black levels however at the expense of a decent amount of light input. At the end of the day I decided to just be content with what I have using the DI iris and that at some point in the future I'll hopefully be able to purchase a projector with better black levels.
post #23 of 36
And remember if you decide to do it right and tilt the ND filter, the further away the surface is from the lens, the bigger the image hitting the ND filter will be, so be sure to try it using a piece of paper instead of the ND filter to see the size of the filter you will need.
post #24 of 36
Of course always use the fixed IRIS if your projector has one, but ND filters are most beneficial for the budget projector segment when they need to reduce lumens and have no other manner. A negative gain Gray screen will work but then you will lose lamp longevity. You remove the ND filter once the lamp gets some wear on it anyhow, so it's not like it'll be a permanent thing usually.

Lots of people use anamorphic lenses and that has more negative effects than the ND filter IMO. The cost is low and these cheap Hoya ND filters do not visibly degrade the image on BUDGET projectors, but I agree I would not be likely to use one on a 4k projector or even a $3000+ 2k projector, mainly because there is rarely a need to.

I don't know where the thread is, but someone did do a double-blind test in the forum using an ND filter and then removing it and using a FIXED IRIS, the people could not tell the difference.

Remember even though the ND filter is interferring with the lens, the optics at the end of the lens are already producing the colors focused in a finished manner so the negative effects of the ND filter are not like as if it were part of the lens element.

I wouldn't WAX my car then paint over the car wax, but it's fine to put the wax on after the fact if you absolutely need to.
Edited by coderguy - 10/6/13 at 5:35pm
post #25 of 36
Do sunglasses made from glass affect the sharpness of your vision, the concept is the same because the ND filter is after the lens (not part of the lens element and it is not changing the aspect of the image).

I doubt a proper ND filter changes MTF / sharpness to the point it was discernible from seating distance (if at all), if you use the correct one and are not causing a reflection. It may produce a different nominal reading in an MTF test, but then that may just be the spectral error margin from reading at a different contrast range.

According to many ND filter testers in a thread that tested expensive ND filters to the Hoya one, there was no visible benefit, I know because I used to recommend the more expensive ones and someone hammered it into my head by showing me 2-3 different threads where people tried to see a difference. Don't waste your money on the more expensive ND filters if you believe those testers, if not, then buy a more expensive one and test it yourself.
post #26 of 36
Mark Peterson measured the MTF reduction caused by my filter. Whether you can discern a 3% MTF reduction in an a/b I do not know. But having an expensive lens, I refuse to diminish its performance just to lower the black reference level. And frankly, purely speaking a ND filter will lower the black ref level but your black ref level with or without the ND filter iwill suck because all projectors still leave a lot to be desired in black ref levels.
post #27 of 36
Quote:
Originally Posted by mark haflich View Post

But having an expensive lens, I refuse to diminish its performance just to lower the black reference level.

I agree, if I paid $25000 for a projector, there is no way I'm putting a $35 lens in front of it, even if I thought it looked the same, it would just bug me to all hell. For a cheap DLP though, the ND filter works great.
post #28 of 36
If you need to use one, it has to be glass type not plastic. In photography, one can see the difference...
post #29 of 36
Yup, the cheap Hoya one is glass believe it or not.
post #30 of 36
Quote:
Originally Posted by timescape7 View Post

If you need to use one, it has to be glass type not plastic. In photography, one can see the difference...
The AR coatings are especially important if it is a screw mount.
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