DV Info Net - Possible Focusing Screen Alternative!

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Possible Focusing Screen Alternative!

Astronomy photographers have to use special focusing screens in their SLR cameras that have higher light transmission and less grain so they can see stars at night. That said, I point you to:

Nikon "D" Screen for F3 Cameras
http://www.bhphotovideo.com/bnh/cont...u=37515&is=REG

It is highly recommended by astrophotographers as a good, no-grain focusing screen for low-light conditions. However, it does not have a convex lens to redistribute the light as normal focusing screens do, so there should be vignetting, although they report it is minimal and does not really show up. I'm ordering it and am going to try it out as a possible GG alternative.

This is mentioned on page 3 of "Just Facts: Another Guide to Digital Filmaking" (on building an adapter) by those who made Marla the Movie:

http://www.marlathemovie.com/bonus/justfacts.pdf

I feel belittled. ;) Edit: Oh I see what you mean. No, I wasn't saying I came up with the idea of using a focusing screen, I'm just saying I found a particular one without grain or light loss. Edit: I'm feeling stupid now. So they do mention the D screen. Well, it looks like it works. I wish this site had a clearer thread that just lays down the summary of what works and what doesn't. This whole board is a bit ambiguous.

Please, if you're going to link to my tutorial, link to the index page which contains a lot of updated info:

http://ideaspora.net/oldskool/

Thanks.

- jim

>>"Please, if you're going to link to my tutorial, link to the index page which contains a lot of updated info:"

Will do. I was copying these from my old links that still appeared to work... I haven't looked at them in a while. Thanks. :-)

Possible Focusing Screen Alternative!

Hi all,
There must be reasons why people are not using Nikon D screen or Beattie intenscreen. I heard beattie had grain visible. Is grain visible in Nikon D screen too? I have following questions on nikon D

1)Do I need to use a condensor or diopter with NIkon D
2)Is the image size obtained on NIkon D big enough to capture from GS400 camcorder
3)Why no one is using it? There must be lot of reasons
4)Does nikon D screen fit 52mm filter ring?
5)I know some folks like Oscar Spier have used it?could they please comment
6)Is there vignetting?

Steev Dinkins uses a Beattie, or at least did, and I didn't mind the grain in his shots. I do mind paying $150 for something I'm going to have to take sandpaper to though to fit in a 55mm filter ring. One slip and you're out a whole lotta cash. I'm curious to see how the Nikon works out.

Quote:

Originally Posted by John McManimie

Thanks, back :)

Sounds like a good piece. Why else would it be used to take pictures of stars, if it introduces grain to the picture?

Could you imagine someone trying to name a newly discovered star, only to find out... :)

Cool! I got the focusing screen today. If you're building the thorlabs tube, there's an easy way to mount it, because of it's ideal size:

http://www.astronautradiomusic.com/nikonscreen1.jpg
http://www.astronautradiomusic.com/nikonscreen2.jpg

Fits right in the spacer.

Careful with the glue! While shooting the pictures I accidentally got a swab of some on the screen. Luckily it came off with a few daubs of rubbing alcohol (hence the q-tip). Do you think it is neccessary to block out the empty spaces around the screen, or can I leave that?

I'll mount it and get some test pictures up here asap.

Quote:

Originally Posted by Ben Winter

I'll mount it and get some test pictures up here asap.

Sounds good, please keep us updated.

I'm very curious to see the results. Could just be what I need...

Whew...what an adventure...

I went out to take some pictures, took some, came back to the computer and realized the GL2 had been in tape mode instead of card mode so no pictures were taken.

Went back outside, took more, came back in, and realized there were smudges on the focus screen from the rubbing alcohol. Not only that, I had been taking only standard quality, 640x480 images.

Went back out, retook 6 pictures out of the perhaps 40 I had taken previously.

A few notes:

Please ignore the vignetting and distortion. I'm using a very cheap canon SLR lens. I popped on a higher quality one and got no vignetting nor distortion, but both the focus ring and the aperture is broken on that one so I couldn't use it for testing.

Also, I'm looking into higher quality macros because these Asian ones are giving me too much chromatic abbheration and aren't really helpful. Once I get a higher quality SLR lens (its in the mail) I'll have a lot more usable space, and therefore won't have to zoom in as much, and therefore won't need as high a power macro. It's a domino effect of improvement.

Here's one I took before I had to retake them (notice the smudge):

http://www.astronautradiomusic.com/AUT_0073.JPG

Here are ones I took later. The grain is definately noticable, but--
Honestly, I'm about 80% satisfied with it. I could care less about grain that small. For my purposes, it's perfect. Plus, the focusing screen isn't just GG--It has a built-in PCXL on one side for even light distribution. Which brings me to: Was i installing it the right way? SLR lens hits GG, which then goes through PCXL, then goes to camera? or does the PCXL go between the GG and SLR lens?

http://www.astronautradiomusic.com/AUT_0074.JPG
http://www.astronautradiomusic.com/AUT_0075.JPG
http://www.astronautradiomusic.com/AUT_0076.JPG
http://www.astronautradiomusic.com/AUT_0077.JPG
http://www.astronautradiomusic.com/AUT_0078.JPG
http://www.astronautradiomusic.com/AUT_0079.JPG

I think the most important part to understand is that these are higher resolution than what native MiniDV captures, so you're not going to see that much anyway. I think a better understanding of what captured video will look like is the first, smaller picture, at 640x480.

I'll repost some pictures once I actually have a step ring to mount this thing to my camera (I was holding it up to the lens the whole time), plus the better SLR lens and a PCXL so I can compare the results with my optosigma GG.

As soon as my back stops hurting from hunching over (I'm 17...@#%*?!!) I'll go out and tape a moving pan, if it's not too dark by then.

EDIT: Well, it was too dark outside so I stayed inside and filmed this. Oddly enough it turned out great with no vignetting or distortion. Or grain (grain that's really obtrusive anyway)

http://www.astronautradiomusic.com/jukedoftest.mov (5~MB)
Thank you Sorenson Squeeze, is all I have to say about that.
Extra points to whoever can name the tune first ;)

For those of you who don't want to download the video, here are some screen grabs. These are probably the most reliable example of what this is capable of because it's directly off the video.
http://www.astronautradiomusic.com/juke1.bmp
http://www.astronautradiomusic.com/juke2.bmp
http://www.astronautradiomusic.com/juke3.bmp
http://www.astronautradiomusic.com/juke4.bmp
http://www.astronautradiomusic.com/juke5.bmp
http://www.astronautradiomusic.com/juke6.bmp

This was shot with the same stuff as those pictures...which proves that the GL2's focus is a very finicky thing. Sometimes you can focus up close...sometimes you can't. Weird.

Ben,
I am interested to see what the shots look like at night - can you give out some sample shots at night to see how well the focusing screen works?