Blue shifts

[Scott Chapin]

I think I have discovered my bleeding problem?

When recording today, I noticed that a slate blue blazer appeared to be a bright chromatic sky blue. While scoping out the bedroom, playing with settings, I noticed that a puple duster was blue.

Chroma level didn't fix it. Chroma phase didn't fix it. Setting the Color Temp to -3 did. Are severe color shifts like this normal?

The blue problem seems to appear under various light sources, and yes, I white balance...to a white card.

[Mathew Evan]

What scene file are you using? I noticed a blue haloing around objects when I overexposed against a blue sky on the 24p setting. Also I have found that under certain color settings in low light that I get excessive chroma noise. It's so bad that it takes on a block like appearance. I'm not sure yet if this a defect or just a side effect of having so many options. I haven't had a whole lot of time to go into detail. Moral of it: Check all settings before you shoot. Especially if you are getting paid.

[Scott Chapin]

This started out being a problem shooting a marching band at wide angles in the Georgia Dome and in an outdoor stadium. The blues were going nuts, and lighting was decent. I just thought the colors behaved poorly due to the small size of the subjects.

Yesterday I was in a light grey conference room, well lit by fluorescents, and was shooting at f/8. The same problem with blues. My bedroom has typical tungsten lighting.

It appears that no matter what color the light source or intensity, the problem is the same. I flipped through all of the scene settings, and they all begged for -3 on the color temperature.

I fear I have a defective camera.

[Juan P. Pertierra]

yesterday i was doing a test in which i was recording myself. I had a bright blue shirt on, and in the recording i noticed the same thing...a blue haze around the blue area, apparently not related to motion.

It seems this is a general defect of the camera. I haven't tried fixing it, but i'm going to try turning the chroma level down since i do that anyways sometimes to get rid of the flourescent reds this camera puts out :)

For some reason, the haze was only visible on the computer LCD monitor. Didn't notice it on the TV.

[Scott Chapin]

Interesting Juan, I notice it more on the TV. But my situation involves high contrast and small detail. I turned my chroma down to -7 and color temperature down to -1, and the problem is greatly reduced. This was under mercury halogen stadium lighting, which might be part to blame, but not totally to blame.

My blues are all visibly lighter. I guess my next step is to try to reduce exposure?

[Jon Fordham]

This is not a defect of the camera, guys. This is simply a problem of NTSC coupled with the compression of DV25 and improper camera settings.

NTSC as the jokes goes stands for Never The Same Color. NTSC is notorious for color issues. Purples are the most difficult to render, Blues are the noisiest color to handle, and Reds are always bleeding.

Add to that the high compression of DV25 and you've got a recipe for disaster.

Improper camera settings is what sets this off. First of, the DVX100 naturally has very high color saturation. So if you are trying to use the "Cine-Like" color matrix, then you're going to have trouble. Add to this that many DVX100 users like to lower the Master Pedastal to get deep blacks. This also saturates your colors when you do this. Not to mention, the Phase adjustment which is almost useless without full RGB shading control. It's really only useful with a SMPTE Type C phosphor monitor for very minor tweaking of the Phase setting. Finally, the DVX100's high resolution CCD's especially when set to Progressive Scan and THIN detail will produce such sharp images that DV25's DCT compression can't handle it.

So what can you do?

First of all, understand the limits of NTSC and DV25. Don't push the color up, the blacks down, the detail up, and phase to whatever looks cool at the time. This will only result in noisy artifact ridden video. Second, forget about the scanning mode. These rules apply to 24P, 30P, and 60i all the same.

Now, if at all possible, get a professional monitor that you can calibrate. Calibrate it. Once you have a calibrated NTSC monitor, you can find settings levels that should be safe.

If you can't get your hands on a profesional monitor. attempt to calibrate your television. This will go a long way fixing alot of the color bleeding issues. Remember, your home televsion isn't designed to show you what you shot. It's designed and cal;ibrated to seel you that television. So the contrast will be too high, the colors will be too saturated, and the sharpness will be overly enhanced.

Atfer you get your television where it should be, try some settings that fall on what might seem like the "bland" side of things.

DETAIL LEVEL -5
CHROMA - 4
CHROMA PHASE 0
COLOR TEMPERATURE 0
MASTER PED -5
GAMMA - NORMAL
MATRIX - NORMAL
V DETAIL FREQUENCY - THIN
PROGRESSIVE - 24P or 30P

Now, while your cam is attached to your live monitor, see if these settings work for you. If not, tweak one at a time and see where they fall.

Things to keep in mind:

Always make sure your television is warm before you start calibrating or adjusting. It takes minimum 20 minutes with a signal for the CRT's to reach a proper warmth to be ready for calibration.

Same thing goes for the camera. Let it warm up a bit before locking into some settings. And don't white balance until the camera is warm and you're ready to shoot. Also, don't forget the black balance. Black balancing after the camera has been warmed for a bit or after several hours of use is just as important (if not more) than white balancing.

Also...

Detail - DV25's DCT compression can't handle overly sharp, overly edge enhanced sharpness. So don't go overboard trying to get a sharp picture. Trying to sharpen will produce worse results than a soft picture. If anything, soften the detail so that the compression can handle it. The smoother the detail, the easier the compression and more pleasing the image.

Chroma - Remember, NTSC can't handle overly saturated images. So don't push it. Cine-Like matrix is basically just overly saturating the image. So use it sparingly if you must. And tone it down when you do.

Phase - The phase adjustment on this camera is really only useful under very controlled conditions. If your monitor utilizes SMPTE Type C phosphors, then after you properly calibrate your monitor, you'll be able to tell if the phase of the camera is skewed one way or another.

Master Ped - This lowers your master black level. And by doing so, it will cause you color saturation to saturate as well. Be careful not crush your blacks to a point that will not only lose shadow detail, but also cause unnescesary color saturation.

Matrix - See above. Remember, Normal color matrix is the chroma level that is normal for NTSC. Pushing beyond this can be dangerous.

Gamma - Note the types of Gamma and the slopes they provide. Cine-Gamma is nice, but you lose Knee. So don't overexpose. Low-Gamma is great for contrast, but also causes the same Master Pedestal issues if not properly handled.

V-Detail - I know there's been alot of discussion with this one. Thick is fine is most all cases. But if you truly want to get a lot of image quality, try setting this to Thin and lowering you Detail Level way down. That way, you're getting resolution, but you're not screwing with the DCT compression too much. Also, don't hesitate to try some diffusion filtering with the Thin detail and the Detail setting at -5 or -6. It yields very nice high res, images without being overly edge enhanced.

24P or 30P - That's up to you. Both are great.

Of course, Purples are still going to be difficult to render, Blues will still be noisiest, and Reds will always bleed. But this approach should take the edge off. It should minimize (if not eliminate) incorrect colors, bleeding colors, and blocky artifacts.

I hope this has been helpful.

[Peter Jefferson]

thank you!!
Finally an answer tho the conundrum!!
and im in pal land and i see this shift sometimes (notice i said sometimes.. LOL)

thanks again

[Chris Hurd]

Excellent post, John -- much appreciated!

[Juan P. Pertierra]

Interesting post John.

Maybe you or someone else can help me with this, talking about difussion filters.

Normally, I want to get the greatest sharpness out of my DVX100 since I work a lot in post and can smooth it down if I want to, so my detail level is usually very high(until now i guess, never considered the artifacting).

I DO have a Tiffen Soft FX/3 which superficially works well as long as there is not too many whites/too bright(gives it that soap opera look then).

To understand the problem i'm having you have to look at a soft fx/3 glass, it has some small curved deformations all over, which are supposed to not be seen, but for some reason on the DVX100, I can pick them out, specially if they fall across straight edges...like the corner of a room.

Does anyone else use any of the tiffen diffusion filters with the DVX, and if so have you noticed this problem? if you want I could post an example of the problem with a screen shot.

Juan

[Jon Fordham]

Juan,

OK, now we're talking!

First of all, turn the sharpness down. Just try it. I promise it will practically eliminate the artifacting. NEVER EVER EVER turn the detail level UP. Always down. IF you HAVE to have more detail leave it 0. But I promise anything more than -3 will be asking for trouble in most cases. Especially if you are shooting in Progressive Scan. Like I said, try by shooting in THIN mode with the Detail setting turned way down. This will give you maximum resolution without causing much aliasing. But you do have to watch out for moire patterns.

Don't confuse sharpness with resolution. Resolution is what we want. Not sharpness.

When it comes to filters, Don't be afraid to experiment. Use them and see what you get. Personally, I like a Soft FX 1 or a 1/4 Black Pro-Mist on the DVX100 in Progressive with THIN mode and the Detail turned down. But that's just me.

Your problem with seeing the actual elements on the filter is caused by the DVX100's small CCD's. Depth of Field is an issue of the imaging plane. The DVX100's 1/3" CCD's are incredibly small. So you have to pay very special attention to the focal length and aperture to avoid picking up the filter elements.

To avoid picking up the filter elements, push in on the focal length a little and open up the aperture. If you're getting too much light, use your ND's to cut down the level. The camera has two built in and they should be sufficient in most cases. I always try to keep my stop between Open and F2.8. This should eliminate seeing the filter elements. Also, the DVX100 has a wider lens than most others in its class. So in most cases you should be able push in on the lens to at least Z10 and not have to sweat backing up to get a wide shot.

Also, one quick note, always bear in mind that a optical filter is totally different than an electronic filter. And while technology today allows us to recreate many types of FX, the knowledge of when and how to use an actual optical filter is priceless. Not to mention that you'll never be able to 100% electronicly duplicate the way an optical filter effects the light upon image capture.

I hope this helps...

[Scott Chapin]

Thank you Jon!

This is definitely "camera bag" material, and it will stay there until it is second nature. You took a lot of time answering the post, and it is MUCH appreciated.

The next $900 bucks goes towards a 5" Sony monitor, maybe. It has only 250 horizontal lines of resolution. Is that sufficient? The model is the: PVM-5041Q

[Stephen van Vuuren]

Probably not, especially for progressive modes. I had a Sony PVM14N6U which did not do a great job with DVX. It did not seem to resolve the 500 lines it claimed. My Sony XBR 32" did a much better job.

I've been eyeing the JVC TM-H1750CGU http://pro.jvc.com/prof/Attributes/p...l_id=MDL101336 for DVX both field and NLE, but unsure about the JVC tube quality compared to other pro monitors.

[Scott Chapin]

Thanks Stephen.

I thought 250 lines would be a little rough, but a 17" monitor is a little big for field work, isn't it? I don't know if I could tote it up a pressbox ladder.

[Stephen van Vuuren]

I'm toying with the idea of using my laptop when I need portable and the 17" for extended sets etc..

Hi-Res 5 & 8 monitors are major bucks.

[Scott Chapin]

Are you implying that LCD monitors would give an accurate depiction of what would be seen on an NTSC CRT?