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View Full Version : How about the "new OLPF" color filter... as a 4x5.65 or screw-on?



Bruce Allen
09-04-2014, 04:00 AM
EDIT: I am only talking about the color filter component of the OLPF. You'd still have an OLPF that removed the moire in front of the sensor. It just wouldn't have the IR-cut / spectral color filtering.

So the new OLPF filters out IR better (and also filters out a little visible light as a side effect) - and this is what improves the color, right? Combined with different color processing...

Could RED (or another 3rd party) make a filter with similar spectral characteristics but as a 4x5.65 or screw-on filter?

Then folks could change between "low light but IR contamination" and "good colors but less sensitivity" by plopping a filter on the front of the camera without having to perform mid-shoot OLPF surgery. We could have a "clear OLPF" on the camera sensor and just change the spectral sensitivity characteristics as needed for the shot.

Anyone with greater light physics knowledge than me think this is impossible (I like to learn so would love a technical explanation)?

For the record, I PERSONALLY like the new OLPF much better and think that RED should just go with the new OLPF... and focus maximum effort on an improved Dragon sensor with better signal to noise ratio and a design that doesn't need lots of black-shading work.

But I know that my opinion is not everything so I thought I'd throw this alternate thought out there. Crazy?

Bruce Allen
www.boacinema.com

Jake Wilganowski
09-04-2014, 07:17 AM
Interesting....

Björn Benckert
09-04-2014, 07:24 AM
Agree, if it's possible to split it up I would rather have the olpf2 part of the equation infront of the lens then behind, just like an IR or ND filter. But I assume it's not that easy...

Bob Gundu
09-04-2014, 07:29 AM
Doesn't the OLPF have to be as close as possible to the sensor?

Todd T
09-04-2014, 07:50 AM
Doesn't the OLPF have to be as close as possible to the sensor?

That is correct, the OLPF has to be specifically positioned relative to the sensor. It has a pattern that corresponds to the pixel array of the sensor that eliminates aliasing/moire patterns.

Optical elements of any kind between the OLPF and the sensor will interfere with the function of the OLPF.

Björn Benckert
09-04-2014, 07:55 AM
That is correct, the OLPF has to be specifically positioned relative to the sensor. It has a pattern that corresponds to the pixel array of the sensor that eliminates aliasing/moire patterns.

Optical elements of any kind between the OLPF and the sensor will interfere with the function of the OLPF.

Yes but the IR cut, I assume could be any where in the chain. So old olpf behind lens infront of sensor and then the difference in between olpf1 and two infront of lens in shape of a normal filter.....

Don't know if thats possible but as I understand thats what Bruce asks for. If that would work I think that would be excellent.

Bruce Allen
09-04-2014, 09:24 AM
Yep. that's what I'm asking for. Thank you, Björn!

The OLPF currently does multiple things: eliminate aliasing / moire AND filter IR (and some visible light, obvious because... well, it's blue if you look at it!).

You'd still have either a v1 OLPF or a "don't filter color OLPF" (eg it would still eliminate a little aliasing / moire) on the sensor.

Then add a filter in front of your lens that does the IR cut. This is obviously possible to some degree, if you look at all of the different IR-cut filters out there.

The question is: are RED doing something more than that, eg using a very expensive / fancy piece of glass with extra properties that would be prohibitively expensive to get in a large size... or something about the way it works means it can't work in front of its lens.

If anyone has a good spectrometer and some courage, I'd love to see what happens if you:
1. point a spectro at a light
2. point a spectro at a light, with an OLPF held in front

Oh yeah... and would it work for MX too? Although I think some of Dragon's better color comes from less crosstalk in the color filters of the Bayer filter itself, which can't be helped.

Bruce Allen
www.boacinema.com

Jeff Kilgroe
09-06-2014, 08:23 AM
And just how would the spectral color filtering become mapped to the sensor through a vast array of arbitrary optics and low-precision lens and filter mounts?

As for IR cut, if it were removed unto external filtration, then we would be right back where we were with the MX and especially the old M sensor. Too many people not understanding or compensating for it, complaining that "such and such camera doesn't need IR filtration, why does RED?"

The OLPF is tuned to work in conjunction with the photo sites or pixels of the sensor and must be placed at a precisely engineered distance to create the proper effect. This is not anything that can be done through an optical pathway that is amorphous or capable of endless permutations and variations.

Gunleik Groven
09-06-2014, 08:24 AM
And just how would the spectral color filtering become mapped to the sensor through a vast array of arbitrary optics and low-precision lens and filter mounts?

As for IR cut, if it were removed unto external filtration, then we would be right back where we were with the MX and especially the old M sensor. Too many people not understanding or compensating for it, complaining that "such and such camera doesn't need IR filtration, why does RED?"

This...

Bruce Allen
09-06-2014, 11:02 AM
And just how would the spectral color filtering become mapped to the sensor through a vast array of arbitrary optics and low-precision lens and filter mounts?

I agree... but if you put a 80A filter in front of a lens, it generally works the same, regardless of lens.

RE: IR cut, certain filters have a vignette effect, others do not so much.

Which is why I ask if anyone has pointed a PR-650 or whatever at the OLPF and seen what it is actually doing spectrally? And what it's like at different incident angles?


As for IR cut, if it were removed unto external filtration, then we would be right back where we were with the MX and especially the old M sensor. Too many people not understanding or compensating for it, complaining that "such and such camera doesn't need IR filtration, why does RED?"

Very true - you see that all the time when people use the Blackmagic cameras. And I do keep criticizing RED for being over-complex, difficult to specify on a rental, etc. Very good point. But the alternative (swappable OLPFs where half the market has v1 and half has v2) is also messy. People will be saying "why don't these two RED DRAGONS match?!" when the A cam is OLPF v2 and the B cam is OLPF v1.


The OLPF is tuned to work in conjunction with the photo sites or pixels of the sensor and must be placed at a precisely engineered distance to create the proper effect. This is not anything that can be done through an optical pathway that is amorphous or capable of endless permutations and variations.

I agree of course... except for the color filtering. I would love to understand why order or distance is so important there - if you cut out certain wavelengths and it's not angle-of-incidence critical, you cut them out, right? Regardless of whether they are before or after the lens. The lens may cut out its own wavelengths too, but I'm not sure why the effect would change depending on the order?

Anyway, thank you for responding and listening as always.

Bruce Allen
www.boacinema.com

Gunleik Groven
09-06-2014, 12:29 PM
I think people will be over-zealous on specifying which OLPF they want.

The FUD on the OLPFs are already all over the place... :)

Bruce Allen
09-06-2014, 01:02 PM
I think people will be over-zealous on specifying which OLPF they want.

The FUD on the OLPFs are already all over the place... :)

You lucky man... in Los Angeles half of the people haven't even figured out that some lenses don't cover 6K.

Seriously. A while back, we helped on a high-budget shoot, with clear pre-viz, specified lenses, etc. All very carefully worked out so that certain zooms and moves in post could be done. They usually shoot Alexa but needed Red for the post zooms.

Get footage back and "hey, we shot at around the focal lengths you wanted... but we changed to an old Optimo and the stupid RED Dragon made it dark around the edges. Hope that's not a problem." This from major award-winning people. They are just not technically-minded sometimes.

And the other issue is: if you have to specify OLPFs on rentals, it makes it tougher to negotiate / beg for the best price. It also give you one more thing to check at the rental house. And it also makes it harder for you to use your friends if they all have different OLPFs.

Again, my personal preference would be for everyone to standardize on the new OLPF... and then RED could just work their asses off to make a revised sensor with less noise and make that as cheap an upgrade as possible!

Bruce Allen
www.boacinema.com

Gunleik Groven
09-06-2014, 01:16 PM
I LOVE stories like that.
Sure. I believe you! :)

Elsie N
09-07-2014, 09:36 AM
With the OLPF choices coming, Cinematographers, DPs, cameramen... are going to have to bone up in order to retain their titles. '-)

Gavin Greenwalt
09-07-2014, 11:09 AM
The spectral filtering and IR filtering could technically be moved but putting it in front of the lens means you would be more likely to get weird IR flares and such.

Robert Ruffo New
09-07-2014, 12:17 PM
With the OLPF choices coming, Cinematographers, DPs, cameramen... are going to have to bone up in order to retain their titles. '-)

That's not what is going to happen, not even close. If a system is too complicated busy DPs, who sometimes have very little time to sleep as it is, will merely choose another camera system that is simpler. Why would they want to bother with something complicated with so many got-cha's?

Joe Kleber
09-07-2014, 12:52 PM
IF there’s a way to eliminate screwing in parts on demand/in the field, please consider it.


IF the OLPF portion could be permanently installed and we could go back to the pop-in magnetic ring idea (perhaps in the front of the OLPF housing, after it’s been installed) for the CC and IR, this would be sooooo much better than the current plan.






If there’s any chance for a compromise here, it needs to happen (IMHO).

Robert Ruffo New
09-07-2014, 01:18 PM
IF there’s a way to eliminate screwing in parts on demand/in the field, please consider it.


IF the OLPF portion could be permanently installed and we could go back to the pop-in magnetic ring idea (perhaps in the front of the OLPF housing, after it’s been installed) for the CC and IR, this would be sooooo much better than the current plan.






If there’s any chance for a compromise here, it needs to happen (IMHO).

That still would not be good enough. Time is money on set (lots and lots of money, unless you are doing hobby shooting)

I have my ear to the ground with a few DPs here in Canada (including myself) who do this as a living. The consensus is that switchable OLPFs are not a viable solution, for unusual apps, like infrared or something, yes, but not to get through a normal day.

Not only that but what if I want clean, non-crushed (forget noisy, the shadows in Dragon OLPF 2 are crushed to mush/clipped) and light sources that are in the shot (like what happens when you shoot at night, really really often) at the same time, we can't because one OLPF gives you the shadows, and another gives you the absent weird reflections - and of course both give you horrible magenta CMOS-smear, the likes of which I have never seen on any other camera, AND gate-shadow in flares.

DPs who shoot Red have to sell it to producers - the default desire is for other cameras that are perceived to be more reliable and/or simpler (rightly or wrongly). I for one would not put my neck out and sell Dragon to producers, because it has so many problems that can bite you in the you-know-what when you get to post and try to grade (I have done hours of Dragon testing).

When you sell something, you're responsible for anything that goes wrong. When you just run with the "standard answer", or what they ask for (which usually, sorry to say it, is Alexa) there might be just as many problems, but you will not be blamed for the limitations of the camera itself since you were just "following orders" or "using what everybody else uses". Thsi happened recently to a friends who had an Alexa completely fail (would not boot again) on set. Everyone just waited for a replacement to arrive, and said "these things happen". If that had happened with a Red camera, after he had pushed for Red over Alexa, they would have held him responsible. This is why Red has to be MORE problem free than the alternatives, not less. Epic MX IS more problem free (in my experience) than Alexa.

I have many times sold both MX cameras very hard, and everyone has been happy. I loved MX so much people thought I was a fanboy. ( I am nobody's fanboy. To me tools are tools, and thats' it. I buy or rent what is best for how I like to work) I still do advocate for MX on almost every shoot we do.

What is really needed is a "Goldielocks OLPF", along with solutions to magenta lines and gate shadow. Then Dragon will be a viable platform for high-cost shooting (as opposed to hobby shooting where if a shot is ruined, it doesn't mean you will be sued for thousands of dollars or possibly ruin your career).

Pros need something reliable, all the time, not something which is spectacular sometimes, but lets you down other times. Yes there are examples of spectacular Dragon footage, but there are also many examples of very weird behavior, where a re-shoot would be needed, in shots where operator error was not the issue (unless you consider doing shots that are no-problem on any other pro camera, including both Red MX cameras, operator error).

Also, yes, Dragon handles clipped highlights better, but MX handles shadows better (side-by-side shooting makes this entirely obvious, and again, DEB and noise reduction cannot retrieve clipped black mush). Only some shots have very hot highlights that go beyond MX dynamic range, but ALL shots have shadows. People saying one "only needs to rate at 250 ISO" do not seem to realize that renting more lights means cutting into already razor-thin margins, and costs a lot more than the price difference to another camera system. Besides, even a completely flood-lit set will still have some shadows, and those do not look nice on OLPF 2.

Until Red sorts things out, I have a wonderful Epic MX, a Red one MX that we still love (and both of which we slightly prefer to Alexa, all things considered, even if Alexa cost the same.)

However, I simply feel that my camera has no viable upgrade options yet, not for pro shooting, in the current reality of lower budgets and higher client expectations, where a single fiasco can put you out of business.

That said, we are considering buying another Red Epic MX.