What I learned today.... at DVinfo.net

Paul Ramsbottom · September 24th, 2006, 12:04 AM

Well, several things:

1. Bob Hart knows wayyyyy too much about light and imaging.
2. Quyen is a good person to listen to about the Letus35A, he builds them after all, fancy that!
3. Focus pulling is a VERY difficult job.
4. Sachler's $25K tripod must be worth the money

So... a week or so ago I started futzing with my new Letus35A and some Canon FL lenses.

http://www.dvinfo.net/conf/showthread.php?t=75687

My early results left a little to be desired (to say the least) but with some good advice from Bob and Quyen I ventured out again today (minus 3 diopters and armed with some great info about setting up my Sony HVR-A1U.

Can't say I am 100% happy yet but I am getting there. My Sony lacks true manual aperture control, so instead I opted to set the shutter speed manually at 1/60th, and controlled the light via ND filters and the Canon Fl's iris. Still getting what looks like a slightly over-exposed image but I think I know what to do next to improve that.

I was using a Canon Fl 85mm f1.8. I am quickly learning that even a moderate focal length like a 85mm picks up every little movement. Think I'll go back to my 50mm f1.4. next week. Note, the pics below show my my camera set-up on a small Varizoom steadicam, which I did use last week but this time around I was using an inexpensive tripod.

Ben Winter also just sold me his Century Optics achromat, so I am looking forward to using that inplace of the standard Letus one. I observed chromatic aberations today (yellow and purple fringing) in the expected high-contrast areas, particularly in the out of foucus parts. I am hoping that the CO achromat and using the 50mm but not completely open-wide (like I was using the 85mm) will nail that.

Well, here's the updated page with clips:

http://web.mac.com/pramsbottom/iWeb/...s%20Tests.html

Ben Winter · September 24th, 2006, 01:42 AM

Paul,
It looks like you're blowing out your diffuser. You'll achieve sharper and more saturated footage if you step down the iris on your SLR lens.

Bob Hart · September 24th, 2006, 07:05 AM

Paul.

If you can hold the camcorder's automatic video gain to 0db with a manual setting, you may be able to get the image darker without bringing up video noise by auto gain digging deep to compensate starving the camera for light.

Ben suggests the diffuser image is blown out. This could well be.

A smaller aperture or ND gel on front of the SLR lens or in the space between the SLR mount and the dust glass on the Letus35 will help. Make sure your Letus35 model has a dust glass in there. The flips have it but I don't know if the non-flip versions do.

If you can't get ND gel, a trip to your local flower seller to scrounge some blue, red and green cellophane bouquet wrapper, stacking three colour layers and shooting through it after doing a white balance will be a dirty and likely colour abberant way of getting ND.

Another trick might be to shoot a test in early to mid morning or mid afternoon to late, with sun behind you and placing a small overbright object in the shot to fool the camera into limiting gain.

I can't see your clips as my computer doens't have Quicktime. If I could get a small clip, say 5mb as a half size frame downloadable or as an email attachment VideoLan will open it for me and my email computer will play it as ancient as it is.

I don't take downloads to the editing computer. I try to quarantine it from virus type mischief.

September 24th, 2006, 12:04 AM	#1
Paul Ramsbottom Regular Crew Join Date: Jan 2006 Posts: 85	What I learned today.... Well, several things: 1. Bob Hart knows wayyyyy too much about light and imaging. 2. Quyen is a good person to listen to about the Letus35A, he builds them after all, fancy that! 3. Focus pulling is a VERY difficult job. 4. Sachler's $25K tripod must be worth the money So... a week or so ago I started futzing with my new Letus35A and some Canon FL lenses. http://www.dvinfo.net/conf/showthread.php?t=75687 My early results left a little to be desired (to say the least) but with some good advice from Bob and Quyen I ventured out again today (minus 3 diopters and armed with some great info about setting up my Sony HVR-A1U. Can't say I am 100% happy yet but I am getting there. My Sony lacks true manual aperture control, so instead I opted to set the shutter speed manually at 1/60th, and controlled the light via ND filters and the Canon Fl's iris. Still getting what looks like a slightly over-exposed image but I think I know what to do next to improve that. I was using a Canon Fl 85mm f1.8. I am quickly learning that even a moderate focal length like a 85mm picks up every little movement. Think I'll go back to my 50mm f1.4. next week. Note, the pics below show my my camera set-up on a small Varizoom steadicam, which I did use last week but this time around I was using an inexpensive tripod. Ben Winter also just sold me his Century Optics achromat, so I am looking forward to using that inplace of the standard Letus one. I observed chromatic aberations today (yellow and purple fringing) in the expected high-contrast areas, particularly in the out of foucus parts. I am hoping that the CO achromat and using the 50mm but not completely open-wide (like I was using the 85mm) will nail that. Well, here's the updated page with clips: http://web.mac.com/pramsbottom/iWeb/...s%20Tests.html Last edited by Paul Ramsbottom; September 24th, 2006 at 01:40 AM.

September 24th, 2006, 01:42 AM	#2
Ben Winter Trustee Join Date: Jun 2005 Location: Hollywood, CA Posts: 1,675 Images: 1	Paul, It looks like you're blowing out your diffuser. You'll achieve sharper and more saturated footage if you step down the iris on your SLR lens. __________________ BenWinter.com

September 24th, 2006, 07:05 AM	#3
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,477	Paul. If you can hold the camcorder's automatic video gain to 0db with a manual setting, you may be able to get the image darker without bringing up video noise by auto gain digging deep to compensate starving the camera for light. Ben suggests the diffuser image is blown out. This could well be. A smaller aperture or ND gel on front of the SLR lens or in the space between the SLR mount and the dust glass on the Letus35 will help. Make sure your Letus35 model has a dust glass in there. The flips have it but I don't know if the non-flip versions do. If you can't get ND gel, a trip to your local flower seller to scrounge some blue, red and green cellophane bouquet wrapper, stacking three colour layers and shooting through it after doing a white balance will be a dirty and likely colour abberant way of getting ND. Another trick might be to shoot a test in early to mid morning or mid afternoon to late, with sun behind you and placing a small overbright object in the shot to fool the camera into limiting gain. I can't see your clips as my computer doens't have Quicktime. If I could get a small clip, say 5mb as a half size frame downloadable or as an email attachment VideoLan will open it for me and my email computer will play it as ancient as it is. I don't take downloads to the editing computer. I try to quarantine it from virus type mischief.