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-   -   Tricky getting the correct exposure with the Sony's particularly the 2100 (https://www.dvinfo.net/forum/sony-vx2100-pd170-pdx10-companion/34693-tricky-getting-correct-exposure-sonys-particularly-2100-a.html)

Glen Elliott November 9th, 2004 08:48 AM

Tricky getting the correct exposure with the Sony's particularly the 2100
 
I just shot my first wedding using 70IRE zebras instead of 100IRE's. I set the exposure so I saw stripes on caucasion faces and in fact the exposure looked correct in the LCD. However after inspecting the footage at home on an external monitor- many of the shots are a hair over exposed. Not blown out but the highlights are a bit hot. Apparently the image was even brighter than my LCD had shown. A double edged sword indeed- because on one hand the dance footage at the dark reception looks much better than I expected- however footage that had ample lighting is a hair on the overexposed side.

Has anyone had this problem with their 170/2100. It seems to be more of an issue on the 2100 for some reason than on my 170 shots. Could it be my LCD is set too dark- or did I just use the 70IRE zebras incorrectly?

Boyd Ostroff November 9th, 2004 09:02 AM

Personally I prefer the 100 IRE setting, but that's just me. It lets me know when something is on the verge of blowing out and I can act accordingly. For example, I might intentionally let a bright spot blow out in order to bring out the detail in shadows or faces.

Initially I had problems getting correct exposure on my VX-2000 so I tried to roughly calibrate my LCD screen (although I think the VX-2100 has a different type of LCD). Plug the camera into your computer via firewire and bring up the standard NTSC color bars so they appear on the little LCD screen. Make sure the ambient lighting in your room is comparable to the place you will be shooting with the camera. Then adjust the LCD. The following link may be helpful: http://www.videouniversity.com/tvbars2.htm

Glen Elliott November 9th, 2004 09:18 AM

That's a really good idea....stupid me- I connected my camera to a tv and used the VX color bars and tried to get it to match my calibrated monitor. Problem is they don't have pluge bars...that's what's important for calibrating luminance for exposure.

Now when I use my NLE to feed color bars to external monitor through my cam....the image will show up on LCD as well. Correct? I never checked because I use a little TRV-33 as a digital/analog converter and never open the LCD while editing.

Thanks.

Boyd Ostroff November 9th, 2004 09:23 AM

Yep, that's how I do it. You are correct that the PLUGE bars are exactly what you need for this. Another approach would be to resize the NTSC bars to 640x480 and put them on a memory stick. Then you could call them up whenever needed in the field. I suppose you could also record them at the head of a tape.

Tom Hardwick November 9th, 2004 10:32 AM

It's not just you Boyd - I'm right alongside you in being a firm believer in the 100 zebra setting. I like to know what's just about to blow, and act accordingly.

Glen - it may be that your Sony is slightly over-exposing in it's factory preset auto mode, in which case you'll have to access the custom preset menu (at the base of the top handle) and dial down the level a click or two. You'll then have to live with 'CP' in your viewfinder, but no worries.

Next time you're filming in the manual mode and you're not quite sure if you've got too many zebras, push the little 'exposure' button to return the Sony to full auto exposure mode, and see what it suggests under those lighting conditions. If I'm unsure I always ask the camera its opinion, and then delve into my box marked 'experience' to decide which way to override it.

tom.

Glen Elliott November 9th, 2004 12:54 PM

<<<-- Glen - it may be that your Sony is slightly over-exposing in it's factory preset auto mode, in which case you'll have to access the custom preset menu (at the base of the top handle) and dial down the level a click or two. You'll then have to live with 'CP' in your viewfinder, but no worries.

tom. -->>>

Actually I don't use ANY auto controls- I use manual iris/gain, shutter, w/b, focus, and audio. I'm a control freak.

Even after setting my w/b with a card I usually have to manually tweak it just a hair so CP is always on my screen anyway. Along with the framing box....love that thing!

One wish....a "push auto" iris button. Now that would be nice!

Tom Hardwick November 9th, 2004 01:19 PM

You didn't read my post Glen. You most certainly do have a 'push auto' iris button.

Glen Elliott November 9th, 2004 02:43 PM

No....it doesn't. The "PUSH auto" (focus) allows you to quickly push the button while it make the auto adjustment and stays when you release your finger.

Hitting the iris button is the same as turning on autofocus. It engages the auto-mechanism for that setting.

Boyd Ostroff November 9th, 2004 04:16 PM

IIRC, pushing the SHUTTER SPEED button will cause the iris to be automatically set for a given shutter speed. I think all you need to do is push that button, but you might need to actually choose a shutter speed. Personally this I find this an annoying feature, but it could be used for what you suggest.

Tom Hardwick November 10th, 2004 02:40 AM

That's right Boyd. Chrome slider in middle position, shutter speed visible in v/finder. Now every time you push the 'exposure' button you toggle between locked and unlocked (ie auto) exposure. Isn't this what you're after Glen? I use it a lot.

tom.

Glen Elliott November 10th, 2004 06:48 AM

I was saying it would be nice to have a button act exactly like the "push auto" focus button. When the button is depressed it would iris automatically- as soon as you release your finger it would lock and keep the setting aquired when your finger was pressed.

What your describing might perform the same task but using other buttons to do so, in a slightly different way.

I just like the convenience and speed of a push auto button...press it in- locks exposure- release.

Peter TK Lee November 10th, 2004 08:36 PM

How about a push button to toggle the steady shot?

cheers,
Peter

Boyd Ostroff November 10th, 2004 08:59 PM

How about an FX-1? According to the manual you can assign steadyshot to one of the programmable buttons... :-)

Peter TK Lee November 10th, 2004 09:05 PM

<<<-- Originally posted by Boyd Ostroff : How about an FX-1? According to the manual you can assign steadyshot to one of the programmable buttons... :-) -->>>

Now that's handy to know. Time to check the manual :)

cheers,
Peter

Wayne Orr November 10th, 2004 10:24 PM

Zebra anomoly
 
In his original post, Glen wrote: "I set the exposure so I saw stripes on caucasion faces and in fact the exposure looked correct in the LCD. However after inspecting the footage at home on an external monitor- many of the shots are a hair over exposed."

It is very likely, Chris, that you have stumbled onto an issue that I have noticed on my PD 150, that I was concerned about, and was confirmed by Alan Barker at his very good site on these cameras at www.alanbarker.com. (Hope Chris doesn't object to this plug, because this site has some great info from a serious documentary filmmaker)

What I suspected, and Mr. Barker has confirmed, is that you can get two entirely different exposure settings using the zebras on a PD150, depending on which direction you come from to arrive at your setting. Confused? Bear with me.

As an operator who has logged many hours of betacam shooting, I use the 70% zebra setting because my primary area of concern is faces, and this is what the 70% zebra tells you. This was Glen's reason for choosing the 70% zebras. If you see the zebras appear in the highlight areas of the forehead, bridge of the nose, or cheek bones, you can be reasonably certain that your skin tones are falling in the sweet area of 65%. This is based on normal lighting on a caucasion skin tone.

You can reveal the 70% zebra by starting at f/11, for example, and opening the iris till you see the zebra pattern appear on the bridge of the nose at, let's say, f/5.6. Very good. But if you start at f/2.8 you will see zebras all over the picture, and as you stop down, the pattern will go away until you are left with the zebras on the bridge of the nose again at f/5.6. This is how it should work, but in practice with the PD150 (and I believe all similar Sony cameras), there is a problem. If you start at f/2.8, and move up to that "sweet" setting, you may end up with zebras on the bridge of the nose at f/4 or f/4.5. This will end up in your subject being overexposed, as Glen has noticed.

Alan Barker noted this same problem and put a scope on it and found the diffence in exposure could be as much as fifteen units on the waveform. This is a pretty dramatic difference in iris settings.

What I recommend (as does Alan Barker) is to always arrive at your iris setting by starting at a closed iris setting of f/11, and opening up the iris until you see the zebras appear in the highlight areas. And remember that the zebras are not the final answer, that there is a bit of "art" involved in this. If you are shooting a very low key scene with no source lighting, you may not wish to see any zebras in the shot, as even a "normal" setting may be too bright for the scene. Conversely, if you are shooting in bright sunlight, and you wish to convey that feeling, you might want zebras over pretty much all of the face to indicate the hot sunlight. This is part of the voodoo that you bring to the shoot. But please remember, that in general, these cameras do well with a bit of underexposure, but overexposure looks pretty ugly. IMHO.

Finally, I don't use 100% because I am interested in the faces, and if you are merely trying to keep your pictures within the 100% area, you are bound to underexpose a face when you don't want to. Through practice, I have learned to look at a scene and tell what is going to happen to the highlights, and if I need to shoot elsewhere, or adjust the lighting. Therefore I don't feel the 100% zebras bring much to the table, versus the all important skin tone exposure reading. But, hey, whatever works for you. (Did I mention learning how to squint?)

I would be happy to hear from any other Sony camera users who can confirm, or reject, these issues with the zebras. It makes no difference whether you use 70 or 100% zebras, you should still find this anamoly of a different exposure depending on whether you come from a closed or open setting.

Wayne Orr, SOC


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