Test footage with LetusXL with 50mm 1.2 at DVinfo.net

Tim Bickford · July 2nd, 2007, 08:24 PM

I thought I would post this... not a lot of action. Kinda peaceful...

I think I may have got a little carried away with color correction.

Anyway - here it is...

http://www.blip.tv/file/288445/

Bob Hart · July 3rd, 2007, 11:20 AM

The XLs have a nice organic look (quoting from somebody else here but it fits so I'll use it.).

Were you mixing Letus and direct-to-camera wides or were they all Letus35? The wides looked sharper than I would have expected for the f1.2 lens. If the wides were on the f1.2 what was your aperture setting?

Tim Bickford · July 3rd, 2007, 05:23 PM

Bob-

All shots were with the Canon XL2 with LetusXL w/50mm lens. I was using a lot of different F stops while shooting. Sorry I do not remember the setting for each one.

Perhaps you can help with a question. I noticed, on some shots, that the image grain was a bit shaky and wavy. Could this be due to weak batteries in the LetusXL?

Thanks...

Bob Hart · July 4th, 2007, 12:10 AM

" --- that the image grain was a bit shaky and wavy"

If what you are seeing are faint soft blotches against a bright plain coloured sky, overcast especially, or the plain side of a passing bright coloured vehicle or bus, that is the "fixed pattern artifact" or "film of grain" referred to in previous posts.

There is not a lot you can do about it except choose your backgrounds, (if it is to be soft, make it dark,) and stay in the region f3.5 or wider on your SLR lens and f2.8 - f5.6 on your relay lens aperture.

You will see the artifacts on this clip ----

http://www.youtube.com/watch?v=-O-Dl7oZTZs

---- even though it is YouTube resolution, as blocking, but in this instance they were provoked to extremity by a shutter speed of 1/400th second against a hostile sky.

If the artifact is actually shimmering or moving distinctly, then your shutter speed may be a bit high. Normally at 1/50th or 1/60th second, the artifact will be seen as faint soft freckles or blemishes which are not shimmering or moving in any other way.

The artifact is related to the motion of the groundglass, which over most of its area is elliptoid ( grain of rice shape ) and canted to the left. This results in two points of slower motion in the excursion at the ends of the ellipse pattern.

You can tune this out a little by selectively rotating the groundglass panel support pillars in their rubber grommets to make the ellipse pattern as circular as you can get it but you won't eliminate it entirely.

http://www.youtube.com/watch?v=yugfv4ZVXgg

When rotating the pillars, do this with a big heavy lens mounted firmly on front to provide resistive mass (handholding is no good as your fingerflesh is too flexible.) You observe the grain by looking through the groundglass at an operating CRT television set screen.

If you can't see the grain, use a whiteboard sharpie to make four little spots in the very corners of the GG to be cleaned off later with a cotton tip or draw whiteout or chinagraph pin spots on the corners of the frame around the GG screen and view the motion with the light from the CRT TV coming from behind.

The motor and GG must be in its normal upright operating condition otherwise you may be tricked into thinking the motion has become circular.

Another artifact which will become apparent is related to video noise generated by a video camera itself, normally masked in detail clutter and only apparent when video gain is cranked up.

This manifests as a fine moving grain artifact which seems to be about 4 to 8 pixels in area.

Tim Bickford · July 4th, 2007, 03:53 PM

Bob-

Thank you! I appreciate your advice.

I read through your unauthorized Letus manual. Setting the Relay lens (rear lens of LETUS35 assembly) to an aperture f5.6. really made the difference. I never noticed your manual until last night. Very nice job… very well written.

Tim

Marty Hudzik · October 25th, 2007, 10:59 PM

Quote:

Originally Posted by Tim Bickford

Bob-

Thank you! I appreciate your advice.

I read through your unauthorized Letus manual. Setting the Relay lens (rear lens of LETUS35 assembly) to an aperture f5.6. really made the difference. I never noticed your manual until last night. Very nice job… very well written.

Tim

To what "manual" are you referring? I have a letusXL on the way and need to get up to speed pronto!

Thanks.

Tim Bickford · October 29th, 2007, 05:20 PM

Marty-

See this link.

http://www.dvinfo.net/conf/showthread.php?t=97868

July 2nd, 2007, 08:24 PM	#1
Tim Bickford Major Player Join Date: Sep 2005 Location: New Hampshire Posts: 448	Test footage with LetusXL with 50mm 1.2 I thought I would post this... not a lot of action. Kinda peaceful... I think I may have got a little carried away with color correction. Anyway - here it is... http://www.blip.tv/file/288445/ __________________ Tim Bickford

July 3rd, 2007, 05:23 PM	#3
Tim Bickford Major Player Join Date: Sep 2005 Location: New Hampshire Posts: 448	Bob- All shots were with the Canon XL2 with LetusXL w/50mm lens. I was using a lot of different F stops while shooting. Sorry I do not remember the setting for each one. Perhaps you can help with a question. I noticed, on some shots, that the image grain was a bit shaky and wavy. Could this be due to weak batteries in the LetusXL? Thanks... __________________ Tim Bickford

July 4th, 2007, 12:10 AM	#4
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,477	" --- that the image grain was a bit shaky and wavy" If what you are seeing are faint soft blotches against a bright plain coloured sky, overcast especially, or the plain side of a passing bright coloured vehicle or bus, that is the "fixed pattern artifact" or "film of grain" referred to in previous posts. There is not a lot you can do about it except choose your backgrounds, (if it is to be soft, make it dark,) and stay in the region f3.5 or wider on your SLR lens and f2.8 - f5.6 on your relay lens aperture. You will see the artifacts on this clip ---- http://www.youtube.com/watch?v=-O-Dl7oZTZs ---- even though it is YouTube resolution, as blocking, but in this instance they were provoked to extremity by a shutter speed of 1/400th second against a hostile sky. If the artifact is actually shimmering or moving distinctly, then your shutter speed may be a bit high. Normally at 1/50th or 1/60th second, the artifact will be seen as faint soft freckles or blemishes which are not shimmering or moving in any other way. The artifact is related to the motion of the groundglass, which over most of its area is elliptoid ( grain of rice shape ) and canted to the left. This results in two points of slower motion in the excursion at the ends of the ellipse pattern. You can tune this out a little by selectively rotating the groundglass panel support pillars in their rubber grommets to make the ellipse pattern as circular as you can get it but you won't eliminate it entirely. http://www.youtube.com/watch?v=yugfv4ZVXgg When rotating the pillars, do this with a big heavy lens mounted firmly on front to provide resistive mass (handholding is no good as your fingerflesh is too flexible.) You observe the grain by looking through the groundglass at an operating CRT television set screen. If you can't see the grain, use a whiteboard sharpie to make four little spots in the very corners of the GG to be cleaned off later with a cotton tip or draw whiteout or chinagraph pin spots on the corners of the frame around the GG screen and view the motion with the light from the CRT TV coming from behind. The motor and GG must be in its normal upright operating condition otherwise you may be tricked into thinking the motion has become circular. Another artifact which will become apparent is related to video noise generated by a video camera itself, normally masked in detail clutter and only apparent when video gain is cranked up. This manifests as a fine moving grain artifact which seems to be about 4 to 8 pixels in area. Last edited by Bob Hart; July 4th, 2007 at 12:23 AM. Reason: error

July 4th, 2007, 03:53 PM	#5
Tim Bickford Major Player Join Date: Sep 2005 Location: New Hampshire Posts: 448	Bob- Thank you! I appreciate your advice. I read through your unauthorized Letus manual. Setting the Relay lens (rear lens of LETUS35 assembly) to an aperture f5.6. really made the difference. I never noticed your manual until last night. Very nice job… very well written. Tim __________________ Tim Bickford

October 29th, 2007, 05:20 PM	#7
Tim Bickford Major Player Join Date: Sep 2005 Location: New Hampshire Posts: 448	Marty- See this link. http://www.dvinfo.net/conf/showthread.php?t=97868 __________________ Tim Bickford

July 3rd, 2007, 11:20 AM	#2
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,477	The XLs have a nice organic look (quoting from somebody else here but it fits so I'll use it.). Were you mixing Letus and direct-to-camera wides or were they all Letus35? The wides looked sharper than I would have expected for the f1.2 lens. If the wides were on the f1.2 what was your aperture setting?