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Sony VX2100 / PD170 / PDX10 Companion
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Old September 17th, 2004, 08:17 PM   #1
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VX2000 : best lens sharpness aperture?

Hi,

Is an aperture for best lens sharpness known for the VX-2000 ?
Most of my footage is of indoor sports, which are poorly light by fluorescent light banks. I've noticed that my footage is much sharper using an aperture of f/4 and compensating for underexposure in post-processing than shooting at a wider aperture with proper exposure. Is the vx2000 lens designed for optimum sharpness in the middle of the f/1.6 .. f/11 range , as with many zoom lenses? I'd like to know this because I have some indoor sports venues in which I can control the lighting.

Thanks for any tips.
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Old September 17th, 2004, 08:54 PM   #2
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Unless otherwise noted, almost all lens will perform at their best about 1-2 stops down from max.

That said, I'd not expect a pronounced change in image focus. I use my PD150's all over the zoom range and don't find issues with focus. At least other than the cameras can be difficult to focus manually in dim light and auto focus almost doesn't work in low light at all.
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Old September 17th, 2004, 09:13 PM   #3
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Most physically small lenses suffer severally from diffraction if stopped down all the way. That's why most of these lenses only stop down to f/8 or f/11. Mike is absolutely correct in stating that most lenses are at their peak 1 to 2 stops down from their maximum lens opening.

The real dilemma is the under exposure of the scene. Usually if the scene is underexposed noise is introduced and negates any benefit gained in sharpness. I generally will shoot for proper exposure or even over exposure (as long as the highlights are not blown) and sharpen in post.

I generally find reduced sharpness preferable to noise in most circumstances. However, it is certainly a personal aesthetic preference.
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Old September 19th, 2004, 04:38 AM   #4
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I agree with Jeff, don't under any circumstances under expose your footage in an attempt to stay away from maximum aperture. Remember too that the Sony lens is way better at maximum aperture than it is at min, but of course that applies to all lenses fitted to Mini DV camcorders.

My Panasonic MX300 appears to contradict this statement in that pushing 'replay' on reviewing the tape shows that incredibly detailed footage is being shot at apertures as small as f16. Of course this isn't so, and most camcorders these days (the VX/PD being a notable execptin) are shooting at f4 with loads if (invisible) ND filtration in the light path. The readout simply tells lies (unhelpfully). The TRV950/PDX10 is shocking in this respect.

My VX2000 is at its best at f4 throughout the zoom range. The lens is slightly flairier at wider apertures, but still sharp. At f16 and smaller it gets horribly unsharp - there's no other word for it. The image vignettes at wide-open, as can be clearly demonstrated by switching on the zebras to 100%.

Stay with wide apertures I say. I find that using both NDs isn't enough on a sunny day, and upping the shutter speed to 1/100th (much as I hate doing it) effectively soaks another stop.

Don't under-expose and post tweak Gints!

tom.
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Old September 20th, 2004, 04:38 PM   #5
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Thanks to Mike, Jeff and Tom for the advice and education !

Gints
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Old September 20th, 2004, 06:00 PM   #6
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Of course there is a question as to what is "proper exposure." Is it where the iris sets it in auto? Is it where the zebras appear on a white card when they are set at 100%? Or, is it when you see zebras on a caucasion skin set to 70%? And did you arrive at that setting by opening up the lens, or closing it down? (You will notice the zebras appear at different f/stops depending on which way you move the iris.)

And what about shooting in the late afternoon? If you allow the camera to select the setting, it will open up till you get more of a "mid-day" look, rather than late afternoon. Is this a "correct" exposure? Here is a link to some material I shot in the late afternoon, using manual exposure to maintain the feel for the time of day. Some may say it is underexposed. I don't know if it is, but I know I like what I see. (about 9megs)
www.digitalprods.com/movies/Sequence2c.mov

Just to be orrnery, I actually prefer footage underexposed by one half to one stop. Seems to have more pop to it. "Correct" exposure always seems a bit washed out to me. However, you certainly cannot go wrong shooting for "correct exposure" and then applying color correction in post.

As long as you are not crushing your shadow detail, I don't think you will go wrong with a bit of underexposure. But, I for one, cannot recommend overexposing in any circumstance.

Just my 2

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Old September 20th, 2004, 06:45 PM   #7
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I'm setting exposure manually with the 100% zebra stripes, opening it up totally, then stopping it down until the zebras disappear almost entirely. With a wide-angle lens and a wide aperture (near full open) that yielded some soft-looking video.
I didn't realize that the zebras would show up differently depending on which way I adjust the iris. Hmmmm.

I shoot martial arts sparring in this garage at a specific time every other week, so changing the time or location is not an option.
The cause of any of the blow-outs is largely due to brightly colored shirts or metallic implements. Most of my video shoots take place in my two car garage under ten banks of 4-bulb fluorescent lights under various angles, so doubling the lighting overall would be a big deal. I suppose I could add some reflective material such as parchment paper.

Thanks for the iris advice,
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Old September 20th, 2004, 06:59 PM   #8
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Just paint your walls a light medium gray! Sort of like a Kodak Gray Card.
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Old September 20th, 2004, 08:53 PM   #9
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OK, Gints, here is what I would do.

First of all, 10 lamp fixtures with 4bulbs each should be plenty of light in a two car garage. I don't think that's a problem.

I don't understand why you would use the 100% zebras??? Do you have white walls in the garage, and you are using them for your white reference? Or, possibly the white uniforms of the students? If the walls are white, are they really getting hit full-on by the fluorescents, or are they just picking up the spill from the lights. If it is only the spill, then they probably will not be close to 100%. More likely, 100% would be the shoulders of the white uniform standing under a fluorescent. If that is what you want to use to set your exposure, then please close the lens toward f/11 and begin opening it untill you see the zebra appear in the shoulder areas. This would be very close to 100%. Notice that this is the opposite way in which you arrive at 100% by going from wide open toward f/11. Please try my way.

But, actually I would prefer you use skin tones and 70% zebras. Pick out a pretty average complexion student and stand him under a fluorescent bank. This should be about the brightest area in your garage. Zoom in till his face pretty pretty well fills the frame (but not full tight), and with the zebras at 70%, go from f/11 toward wide open, and watch for the zebras to appear in highlight areas on his face, such as the bridge of his nose, forehead, or cheek bones. When you see a bit of zebra in the highlights, stop and use this as your f/

stop. You might try this in different areas of the garage, and hopefully you won't have more than a one stop difference in the various areas. This means you are free to shoot without worrying about the iris.

You might check the 70% iris setting with the camera's auto iris: line up the shot on the student as in the above scenario, then with the camera in manual iris, stop down all the way to "close" or f/11. Now, press "auto" iris control, let the camera set the exposure, and release the iris button, locking the setting. Hopefully you will be within about a half stop of where you arrived at using the earlier method. I'm betting the camera will tend to overexpose a bit more than using the manual method with the 70% zebras. IMHO, video cameras all tend to overexpose a bit, but we are not talking major differences here.

As a final step, you can check to see what happens when you switch on the 100% zebras. If you find that my suggestions leads you to overexpose the uniforms by two or more stops, then you will have to stop down even more, which will underexpose the flesh tones a bit. But I'm betting you'll be alright.

BTW, if you can manage with the help of the ND's to shoot around f/2.8, you should get pretty much the best the lens can do, and give you good depth of field for focus. I really can't believe with all those lights you would end up shooting near wide open, unless you are using a heavy ND. You're not shooting at a fast shutter speed, are you?

Let us know how it works out.

Wayne
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Old September 20th, 2004, 08:55 PM   #10
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Good suggestion. The walls were originally blue, primarily because the fighters showed up with grey or black clothing .
A few weeks ago, I did paint the walls a light grey. They were looking a little dull, so I mottled up the walls with some slightly darker gray. Also, I added a mural on one of the walls as well.
Yes, I just killed my grey card and increased the load on the MPEG2 encoder, but I just couldn't stand the monotony of a uniform grey.
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