Overscan in VX2000 LCD

[Paul Tauger]

I've previously reported that the Optex .65x wide angle lens (which has front threads) doesn't vignette -- this was based on looking through the viewfinder and at the LCD on my VX2000. Well, I've gotten my tape home, captured all 10 hours of it, and found to my dismay that the Optex DOES vignette with a standard UV filter in place. What's particularly annoying is, evidently, both the viewfinder and the LCD screen on the VX2000 overscans enough so the vignetting did show.

Why in the world would Sony design the viewfinder and LCD to overscan?

Fortunately, the vignetting is slight and won't show on any of the televisions for which this footage is destined, but I'm ticked -- I shot this in India, and it can't be replaced.

Aaaaargh!

[Mike Rehmus]

Paul, sorry that your footage is somewhat damaged.

I wasn't aware that the cameras displays are overscanned. Can you measure the amount of overscan and give us the results? I don't think my PD150 displays have overscan. I measure it when I get mine back and report.

It is possible that the 2000, being the consumer version of the camera tries to keep the user out of trouble with the other side of the issue. If they frame everything just within an non-overscan viewfinder, they will complain that some of the picture was 'missed' by the camera because their TV set overscans.

As you point out, the vignetting won't be visible to most viewers although I don't know if plasma and LCD television displays overscan or not. I'd guess they do.

[Wayne Orr]

Excuse me, Paul, but let's talk about that UV filter for a moment. If you put a UV on the front of the wide lens, then it is most likely the filter that is vignetting, not the lens. I would have to say it is your fault, rather than the lens manufacturer. As we have all said many times before, new gear should be tested before shooting any valuable footage. BTW, that wide lens is used extensively by the BBC.

But it sounds like you only see the vignetting on your computer monitor, and this "problem" will never be seen on any normal broadcast television. And the overscan on the lcd is pretty common knowledge. About the only thing the lcd should be used for is to confirm your white balance is in the ballpark and basic composition. If you have critical issues, you need an external professional monitor. Your lcd should not be used for critical focus or exposure settings. Everything tends to look good on the little lcd.

If you really want to know how much your lcd is overscanned, you can save a registration chart or similar to your memory stick and call it up in the camera. The display on the lcd will indicate what you are missing. Synthetic Aperature's website is a good place to download free test patterns.

Wayne

[Boyd Ostroff]

<<<-- Originally posted by Wayne Orr : Synthetic Aperature's website is a good place to download free test patterns. -->>>

Thanks for that tip! Their free "test pattern maker" is very cool:

http://www.synthetic-ap.com/downloads/dotpmm.html

I had noticed the overscan issue myself awhile ago. According to the "overscan percentage" test pattern at the above link, the VX-2000 overscans by 3%. If I crop the test patten in Photoshop so that it matches the VX-2000's LCD screen, the image is 670x462. I would be very surprised if this were different on the PD-150, but perhaps someone can perform the same test and report back.

FWIW, the Sony .7x wide converter does not show any vignetting, and some tests I did awhile ago didn't show any noticeable distortion or focus problems.

[Rhett Allen]

I actually did the test about 10 months ago on the PD-150 and it does indeed overscan by about 3-5%. Coming from a photography background I fully expected it to not show 100% of the camera image (very few cameras do) and so I did the test just to get an idea of it's range. I just shot a full frame resolution chart and compared the results on the camera, the computer and the NTSC monitor so I could reference it.
It is always best to do some test shooting and KNOW the limits of your equipment before you ever actually begin a shoot, it's much easier than trying to fix something that comes back wrong. And don't take someone else's word for it, check it yourself.

[Paul Tauger]

Wayne, I mis-wrote-- it is, of course, the filter that is causing the vignetting, and not the lens itself. There is no vignetting when the lens is used without filters or, for that matter, with a low-profile filter.

I had shot test footage before taking the camera to India. However, the vignetting seems to appear only at certain aperatures and, as luck would have it, my test footage didn't reveal the vignetting problem.

The vignetting is, indeed, only visible on my computer monitor, and doesn't appear either on my primary editing monitor, or the television I keep in my editing room to "check" edited footage. The vignetting will be noticeable only if the final edited DVD is played on a computer. I'm seriously considering apply slight cropping to the entire project to eliminate the clipped corners.

[Mike Rehmus]

How about compensating it with something like After Effects?

A graduated mask could be created that would correct the brightness in the corners, making the issue much less noticable.

Of course photographers burn in the corners of their prints to focus the viewer on the image.

I hadn't measured the 150 as of yet but thinking back, there is some obvious overscan. Worse, it may not be centered on the video field either. Another issue to check out when I get the camera back.

BTW, IIRC, my Nikon F3 provides a 100% field of view image in the viewfinder. Now if I could just get a video sensor back for that camera, I'd be in great shape. Hang a firewire drive on a belt and be off and running.

[Scott Shuster]

What exactly is 'vignetting' and is any of this an indication that I should think twice about buying a wide-angle lens?

[Boyd Ostroff]

Vignetting is a darkening or even cropping in the corners of the image, where the cylinder housing the lens is visible. I think the original concern in this thread centered around the fact that no vignetting was visible in the viewfinder (or on the LCD screen), but that it appeared on the computer screen during editing. This is due to the fact that most TV's and even the PD-150 LCD screen don't show the edges of the image.

[Wayne Orr]

Good explanation of vignetting by Boyd, but to answer SShuster's question; absolutely not. A good wide lens converter should be one of the very first accessories you purchase for a VX2K or PD150, as the built in zoom lens is not very wide at the wide end. Vignetting will not be a problem with any of the quality lenses, such as the Sony, Century Optics, Optex, etc. If you are getting a lens that is quite a bit less expensive than the above, you might want to test it before buying.

Other items to watch out for; wide angle barrel distortion (all "zoom through" lenses will distort to some degree), focus at various focal lengths (a good lens will hold focus as you "zoom through" its range), and sharp focus at the long end of the zoom range (less expensive lenses go soft at the end of the zoom).

There are other items to consider, such as the Sony lens has an especially large front element that is prone to flares, and will limit you to large 4x4 filters (which are expensive). But man, it is a good, sharp lens. Century Optics offers a wide converter that has a bayonet mount that goes on and off quickly and securely. Canon makes a good converter that comes with a lens shade, and costs less than the others, but it goes soft at the long end.

But do get the wide angle converter.