How to mount wide angle lens

[Samuel Birkan]

I just got a Century wide angle adapter for my 950. I keep a UV filter permanently on the camera lens.
Does it make a difference if I mount the lens on top of the filter or remove the filter first?
To my naked eye I cant see a difference. Does any one know if there is a "correct" way to mount this.
By the way I previously had the "cheap" Sony wide angle and the quality difference is noticable, just the weight of the Century is almost double that of hte Sony

[Michael Brumback Jr.]

I have a PDX10 and I mounted my Century lens right to the camera, then purchased a UV protector for the wide angle lens. Because when you put out that amount of money for that lens, you need to protect it more than the smaller lens under it.

And I'm not sure of how the lens was developed, so I'm guessing here, but I would image you should have nothing between the lens and the camera, just incase the lens was developed on certain distances from the CCD.

Yes it is a heavy lens, but you will find your shots have a bit more to them now because that weight helps smooth out small movements.

mJR
www.mjrworld.com

[Boyd Ostroff]

Two concerns with the filter between the lens:

1. The filter might not be strong enough to support the lens if it's heavy. Probably not an issue, but it's possible the lens could fall off in an extreme case (like bumping it).

2. I think the main concern would be vignetting (cutting off the corners of the image). You probably won't see this on the viewfinder or LCD because they overscan (don't show the entire frame). Capture a little footage with the lens on the camera and set for full wide zoom. Look in your NLE then, which should show the full frame. You can check to see if the corners are vignetted.

Michael also raises a good point about the distance from the lens to the camera, but I'm guessing this will be less of an issue. Again, check the image in your NLE. You could also snap a still photo since that will be higher resolution and use the full surface of the CCD. Any problems should be more obvious when you view that JPEG on your computer.

[Samuel Birkan]

I tested over the weekend with the filter on and off.
As far as width and clarity there was no discernable difference.
The shots with the filter on did show a tiny bit of vignetting (these were stills) at the widest zoom.
I was a bit surprised by the barrel effect, it was very obvious in photos of a brick wall, not so obvious in a general landscape type picture.
As Michael mentioned, the first thing I did was to get a 62mm UV for it.

[Michael Brumback Jr.]

yes, when you pull back to the wideset angle you will see some curvature. usually you won't notice it that much when filming motion and things indoors, which is why I purchased that lens. but when outside with buildings and trees, I usaully zoom in a tad and it's ok.

you can put 2 filters on the lens before you see the edges in the frame. I also purchased a 62mm .9 ND filter for the bright outdoors.

with the lens zoomed all the way out it's about a 30mm lens, I believe. this is what my 3d tracking software calcualtes it as when I track my video and send that data to my 3d animation software.

I hope one day to track the camera at EACH ZOOM TICK MARK with the .65 wide angle lens off and on to get a "rough" estimate of what milimeter equivilant you are using.

michael JR.
www.mjrworld.com

[Boyd Ostroff]

<<<-- Originally posted by Samuel Birkan : The shots with the filter on did show a tiny bit of vignetting (these were stills) at the widest zoom. -->>>

That isn't surprising, but shouldn't be an issue for you (unless you need to shoot stills). On the TRV-950 the only time the whole CCD is used is in photo mode. Shooting 4:3 video uses a smaller rectangle centered on the CCD, 16:9 mode is slightly wider but not as tall and it still does not use the full CCD width. This should also minimize barrell distortion in video mode since you won't see the edges of the image.

This is something we've discussed here before. Sony deliberately crippled the TRV-950 through firmware so that it is lower resolution than it's pro cousin, the PDX-10. The PDX-10 still doesn't use the full CCD in 4:3 mode, however it does use the full width in 16:9 and also more height than the TRV-950. This makes it a little more sensitive to vignetting in this sort of situation. But it sounds like you've done your homework and found workable solutions.

Regarding focal length equivalents in 35mm still photo terms (which is what I assume you're talking about Michael). Take a look at your manual, it will give those specs for the camera's lens at each end of the zoom range, which will be different for 4:3, 16:9 and still photo modes. Now just multiply those numbers by .65 and you'll have the 35mm equivalents for your lens.

[Michael Brumback Jr.]

here is an image to display the amount of distortion with the Century .65 lens full wide

http://www.mjrworld.com/sonypdx10/pdx10_.65_distortion_mjr.jpg

as you can see in my case on my green screen, it's important to have an undistorted image or the 3d tracking software cannot figure out straight lines, until I tell it what is suppose to be a straight line.

other wise it will track wrong, also when I composite back in 3d objects they need to have the same distortion on them, because the background live action plate will have distorted, curved straight lines and all my 3d objects will have perfectly straight lines.

michael JR.
www.mjrworld.com

PS yes that is my garage with the garage door opener right there in middle top of my screen :(

[Boyd Ostroff]

That's very cool Michael; but where do you park your car? ;-) Are you getting good results with your PDX-10 for compositing? This is something I may need to get into myself.

FWIW, on the PDX-10 the lens is spec'ed at 49-588mm in 4:3 mode, 41-492mm in 16:9 mode, and 41-492mm in still photo mode. The numbers will be different for the TRV-950 since it samples a smaller area of the CCD.

[Michael Brumback Jr.]

thanks, I park it outside, and it's snowing today here in the windy city :( oh well, the art comes before anything else, well it's right after God, my family, and my country

then it's my art :) car is just a car in the end.. art is forever

yes and no. DV compression in itself is a pain when it comes to Chroma keying. if I would have gotten my butt in gear years ago, I would have tried hard to save for a use Betacam deck or something analog, just for effects, but then the quality wouldn't be as good.

I have pulled decent keys with Combustion, there not perfect, but good enough to work within the technical limitations of 4:1:1

The camera does a great job of color and quality of the image, compared to say my mother's 500$ Canon Elura. but DV in itself is not 100% for chroma.

if you look at my page I will be posting some new comps and test I'm doing as I work my way up to a short.

mJR