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Purple filter can improve Image on GH1/GH2..?!? Project Blue Light
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  • Wow, I don't even know where to begin... Yet again you are working with a sensor that has a limited dynamic range. The only way any color filtration filtration would be useful is to measure what is the color temp of the light that would provide the widest dynamic range for each of the groups of the sensors behind its respective colored filters and then walk around with the set of the filters (just like in the film days) and use them accordingly after measuring the spectrum of the scene light with a spectrometer, in effect linearizing the sensor to its optimum behavior. Now let's assume for a moment that the people at sensor design lab at Panasonic are not complete idiots, let's assume for a moment that the color science guys are also not complete idiots at Panasonic and the sensor is actually build and tuned to run well at lets say 6500K (most likely). That assumption makes it so that white points of green, red and blue sensors are roughly at the level when exposed at that light with an appropriate (Daylight) setting. Then, by applying the purple filter you are lowering the dynamic range, artificially clamping green channel by underexposing it. Then you have to stretch it later later in post, lowering the number of real shades of grey in the green channel. On an 8 bit image. Creating banding. You guys will always hunt for some pseudo science voodoo, Go out and shoot. I have a fuel magnet to sell to you.

  • @CRFilms @dkitsov ...yes never shoot with ND filters outdoors, just use shutter and apature to get the best image. >_> Logical fallacy. ND filter ideally should not change the color balance neither should the aperture/shutter speed combination. This discussion is about changing the color of the light that reaches the sensor sights, not about the means of overall exposure control. Sensor needs as much light as it needs. Ways of limiting it with ND or shutter/aperture, while makes aesthetic, difference probably makes no "electrical" difference as far as ISO adjustment is not involved (that would move the sensor from the optimum operating range)

  • @dkitsov ...you said"BS. Lets improve image by letting less light to the sensor."

    So...you were the one who started talking about "light" not color. Sorry if my comment out sarcasm'd yours. ^_^

  • All the theory talk means nothing if the final results prove to be an improvement! Theoretically Bumble Bees shouldn't be able to fly... If the guy is finding visual improvements using his filters, then perhaps there's something happening that the sensor theory isn't taking into account.

  • Hi, I'm that guy with some years of experience in tv and film industry, and have also studied the subject of photochemistry in university for a few years. The benefits of using a color filter have become obvious. It is a combination of several factors. It's true that the Green channel gets compressed, but it is already of very good quality so the benefits outweigh the negative aspects.

    In the 2008 tests they found improvment from using a magenta filter even for 4:4:4 material. The few comments above completely ignore the fact that for video the data is turned into YUV format and a lot of color information gets simply discarded and tossed away. Any extra color bits will help encode the color channels better. This is achieved using a color filter. If all channels are recorded on the same relative levels (no color filter), this is a license for the video encoder to discard color bits. Using a color filter over-saturates the color so the video encoder is no longer licensed to discard as much color as before. This will help in post while grading. There is no other way to achieve the same results other than coloring the lights.

    No technique will repair the colors in post that have been compressed too heavily. It is true that it will be difficult to WB the colors to baseline, but do you always want that? All the extra color can be used to grade the material to one's liking with better quality than before. And the improvment in color rendition is substantial. I have a small demo video filmed in rather extreme lighting conditions.

    In this case it was possible to change the colors for the primary palette (light with outdoor color temperature) and the secondary palette (light from LED lamps). There is no substantial light loss because of less noisy and higher quality material. Anybody has to evaluate whether the colors achieved this way can be used for certain purposes, but they will be better quality and grade more easily.

  • @aki_hartikainen From what I gather, your recent color filter tests were all done on the GH1. In my experience, that camera has a greenish cast, compared to the GH2. When shooting footage on the GH1, I correct for this by setting the GH1's WB+ adjustment to M-5 (after setting the white balance for the scene). That seems to do the trick:

    In the video above, the first clip is from the GH1, the second from the GH2, and the third from the Nikon D5100. Color correction was done on the GH1 in-camera.

    On both GH1 and GH2, there's an easy way to check out the individual R, G, and B histograms before you shoot. Make sure the camera is set to sRGB mode, and that Manual still photo mode is set the same as Creative Movie Mode (in Manual exposure mode of course). Then frame and expose your shot in Creative Movie Mode, and switch to Manual photo mode to snap a still frame. (This insures that your still photo settings match your video settings.)

    In Playback mode, you can then display the individual R, G, B, and Y histograms next to the photo and compare their levels. When I do this with a broad-spectrum scene using my M-5 setting, all three color channels turn out reasonably well-balanced, and require no further color correction.

  • What does this mean ?

    Очень низкая чувствительность красного канала относительно зеленого (баланс белого на 1.6 стопа)

  • Very low sensitivity of red channel compared to green channel (white balance on 1.6 stops)

  • So the choices are :- Correct WB for daylight and well lit scenes. For low light=

    1. use 5000K WB

    2. Alternatively use a 85b or magenta filter and accept 2/3 stop light reduction.

    3. WB set at correct color temp (or 3200K) pushed about some clicks to blue and some down towards magenta.

    Is this a reasonable summary ?

  • http://provideocoalition.com/index.php/aadams/story/cameras_now_its_rocket_science/

    VK posted a snip-it of this on another topic and the most interesting thing was the poster saying that on The Red camera he used blue filters to improve the image. He also goes into different cameras strengths and weaknesses and that you have to shoot with them in mind.

    I'm not sure anymore about how much a filter can improve FPN, if you got it bad, it's bad, but outdoors in daylight, I'd defenitely use a color filter. Changed topic title to reflect current topic thinking.

  • I feel like banging my head over the arguments on that thread. Somewhat glad that kholi shut down the thread. AAAARRRGGHHH

  • Looks like there is still room for improvement even for GH13.

    The hack settings that I hastily created (25p iW) as a last ditch attempt to cure the false contrast and aliasing in Native settings are the most organic and cinematic I have received from this camera thus far. I am going to look into the compression as soon as I get a production filmed with the current settings. If the compression could be improved slightly, I don't think I will be needing a GH2 anytime soon.

    Also, the planned comparison of the colors to actual film stocks will begin as soon as possible.

  • I'd still love to see some comparison footage that shows the claimed improvement, even if Aki threatens to sue me again.

  • Aki. Any claims are pointless without raw unmodified footage straight from the camera.

  • I tell you what...I invite those of you arguing to go out and test it for yourselves to prove or disprove this theory. @nothing...don't bring the arguments over here please. It's really because of you that the thread was shut down. If the guy will not budge on what YOU want then maybe it's just time for YOU to go out and prove he's wrong. Don't turn this into another he-said-she-said kind of argument. If you just don't want to try it yourself and chose not to believe his argument...then just walk away. Honestly Aki isn't bringing up anything that I have not heard of before and I understand what dikitsov is trying to say earlier...but...prove it right...prove it wrong or...just stop guessing/arguing.

    @Aki...my suggestion to you is this: There have been many requests from folks here asking for you to do a before (Raw/AVCHD file from camera) and after with video. Before responding to any other threads about the benefits of this or that....just produce what the readers want to see. I understand you want to demonstrate your workflow.....but let that be last on the priority list. I think some just don't care about workflow until they see "actual" results from a before and after video. It's at that point where a workflow will make sense (or not) for everybody.

    EDIT: @nothing and @zcream FYI...it's not that I don't agree with you btw.

  • I have shot with colored filters on many different cameras before. The concept is nothing new but rarely used with digital, we used 85 filters with film every day - but those and the related 80 filters were used to get CORRECT color balance (including the referenced use on the original tungsten impaired Red One sensor), not to throw color balance completely off.

    I noticed no improvements of the sorts mentioned here on digital, only later difficulty color correcting back to normal when shooting with wacked balance - that's why I've asked to see examples from those who have said they've seen improvements. I'd love to learn about a useful technique, but I must be looking in the wrong place for the difference - I'll need it pointed out.

    I don't "guess" about cameras, btw, I know from experience.

    The thread in question was shut down because of Aki not backing up his claims when asked (by many including moderators) and then threatening to sue members over it.

  • Several days ago I politely asked to move the thread under work flow and that seemed to have sparked more obscure demands and misrepresentation of something that were not my words, opinions or intentions. A day or two after that with no reply for my original request to move the thread it was locked and some untrue claims were left as the last words by member 'nothing', which I first, again politely, asked to be removed or evidence for said untrue claims were provided. Again receiving no reply from anybody I had no choice but to demand the last comment to be removed. That is the story of it from my part and easily verifiable.

    Now back to the original subject, demonstrating that purple filter is better than without would be like demonstrating that Nostalgic picture profile is better than Smooth. Some would agree, some would still prefer Smooth and see no point in using Nostalgic picture profile. It has been agreed by many that the filter compresses contrast. This is the same thing as having a flatter picture profile. If it can be agreed that flatter is better for grading, then that will be the end of the argument. That was what I originally hoped to achieve, better gradability. It did help with the FPN of the GH13 to the point where I can now realize scenes without much FPN. This same effect has been reported by others.

    I graded the attached file in PS only, and the rather unimpressive but clearly flat source image turned out fine and took the grading well. Perhaps a bit too flat for a source this time. You could see that the dark values have been recorded and compressed between values RGB 30-50. This helped capture the dark hues of the image unposterized.

    flat.png
    1280 x 360 - 620K
  • It is very important that as many people as possible put as much stuff as possible between the camera and the scene. In fact, I recommend at a minimum a bag of wood chips and a slurpie.

  • @DrDave I have made resolution tests with not just one but two glass filters on the lens. The resolution still exceeds the camera resolution at 4k image size. Those tests can be found from my site as an update to the Project Blue Light (links above).

  • @zcream What is your opinion, is flatter image better source for grading? If yes, how would you go about it to achieve flatter source?

    @nothing What causes flatter compressed image to be of better quality after grading once the contrast has been adjusted to normal?

  • Rather than be drawn into an argument meant to distract from your previous claims (although I'm still not sure how more saturation equals flatter, suffice it to say that flat is not best for all situations), I'll restate the question you threatened to sue to have deleted elsewhere: Are you backing off the claim of "no posterization ever" as a result of shooting with a colored filter? You claimed such in the past in order to garner attention, you even posted a photo with it emblazoned across the top (which you have since edited, don't worry the original is archived and will be provided to the court). Admit that you overstepped in your claims and stop lying about it, and we can all move on. Keep claiming otherwise and you will continue to be called out on it.

    Here is something I think you are confused about: there is little interest in the workflow you invented - there are far easier ways to nondestructive grading. The claims of the benefits of shooting with a colored filter are the only thing that has drawn attention to this discussion.

    If you wanted this line of query dropped, threatening me is the wrong way to go about it.

  • @nothing "Are you backing off the claim of "no posterization ever" as a result of shooting with a colored filter?"

    Please provide evidence for your claim.

  • I'll take that as a yes.

    I don't think you've done anything of note in this area, but thank you for your efforts. Your claims of completely eradicating posterization and banding by using filters were the only thing that interested me here. If you are no longer claiming that, and only claiming subjective gains with your post methods, then I, and many others, will have no further interest in your project.

  • The research will continue and even better results should follow. Obviously you are going to have to follow the Project Blue Light website now if you wanted to learn more about it.