I finally have a Canon and a Letus!

Stathis Athanasiou · January 19th, 2008, 02:00 PM

I haven't had time to test the difference between open and closed iris on the camera. Thinking about it, I believe it wouldn't make much of a difference changing the iris on the camera lens, as opening and closing the iris on the photographic lens itself. Because changing the camera iris doesn't change how the scene is perceived by the photo lens, which is what matters when using the Letus.
But that has yet to be proven by test.
(tomorrow maybe)

Oleg Kalyan · January 19th, 2008, 08:53 PM

Great, look forwards to your test,
and appreciate your effort, we all as a community learn here!

Stathis Athanasiou · January 21st, 2008, 01:54 AM

Ok, here goes.
I shot some flowers with varying ND, F stop and shutter trying to get the same exposure. I didn't use a monitor or waveform to judge accurately, but I think the results are obvious.
So, if you step down the camera using ONLY the shutter speed, with iris wide open and Shutter at 1/25, then the ground glass can be clearly seen on brightly lit areas.
If you step down using ND and/or F stop, the image looks clearer.
I believe that using the highest possible F stop on camera, then the image will be clearer, and this makes sense if you consider that you increase the depth of field this way, so the ground glass is sharply focused, as opposed to having an open iris and a more shallow depth of field.
Of course this is not a scientific test, as no scientific instruments were used, nor was a scientist present. And we all know that these are though times for scientists with 2012 approaching and all.

Oleg Kalyan · January 21st, 2008, 04:21 AM

Thank you for your test, pictures look very sharp.
Good to know you can still shoot wide open on camera, so that light loss is minimal, I mostly concerned about low light shooting, and possible light loss.
The lowest f stop on camera is 1.7 did you have to zoom in more, so that it become 2.4?

Thanks again.

Oleg.

Stathis Athanasiou · January 21st, 2008, 05:26 AM

Yes, the zoom reading was 1.4m and F2.4 was the most open at this length.

Brandon Freeman · January 23rd, 2008, 05:39 PM

What were the settings for the last picture you posted? I'm seeing an artifact on the out of focus light in the background there not seen in the other photos -- like you can kind of see the pin of light through the bokeh. There's documentation of this artifact elsewhere, but you seem to be avoiding it in all the other photos.

Do you remember what settings you had for each photo?

Stathis Athanasiou · January 23rd, 2008, 05:49 PM

Brandon, if you roll over with your mouse you can see the settings for each photo.

Stathis Athanasiou · January 23rd, 2008, 05:50 PM

no ND
F 9.5
S 1/50

I haven't noticed it until now.
What is it? Is it random?

Brandon Freeman · January 23rd, 2008, 06:02 PM

Well, I can't find the other thread, now, but YAY! I actually don't have the Letus Extreme yet (should be here soon), and this artifact was a concern for me till now. It looks like the camera iris needs to be kept fairly open, or else somehow the bokeh is slightly see through. Makes no sense to me, but it is a great relief to know how to work around it.

Bummer about having to keep the camera open, though, because that means it'll be harder to focus on the ground glass (I'd think).

EDIT: Keep in mind my sole form of education in all matters is trial and error -- I'm sure there is someone more "head-learned" than I who can make sense of this in a technical way.

Me, I's just happy 'bout the purty pictures. :)

Stathis Athanasiou · January 23rd, 2008, 07:12 PM

Quote:

Originally Posted by Brandon Freeman

Me, I's just happy 'bout the purty pictures. :)

I second that !

Brandon Freeman · January 23rd, 2008, 08:51 PM

Found the thread:

http://www.dvinfo.net/conf/showthread.php?t=106882

Stathis Athanasiou · January 24th, 2008, 03:27 AM

Thanks.
From what I see from the pictures I posted, using ND and having the iris wide open, produces a sharply focused ground glass that doesn't show through.
To my eyes the sharpest picture is the one with ND1/32 f2.4 S1/25

January 21st, 2008, 01:54 AM	#18
Stathis Athanasiou Regular Crew Join Date: Jun 2007 Location: Athens, Hellas Posts: 73	Ok, here goes. I shot some flowers with varying ND, F stop and shutter trying to get the same exposure. I didn't use a monitor or waveform to judge accurately, but I think the results are obvious. So, if you step down the camera using ONLY the shutter speed, with iris wide open and Shutter at 1/25, then the ground glass can be clearly seen on brightly lit areas. If you step down using ND and/or F stop, the image looks clearer. I believe that using the highest possible F stop on camera, then the image will be clearer, and this makes sense if you consider that you increase the depth of field this way, so the ground glass is sharply focused, as opposed to having an open iris and a more shallow depth of field. Of course this is not a scientific test, as no scientific instruments were used, nor was a scientist present. And we all know that these are though times for scientists with 2012 approaching and all. Attached Thumbnails

January 23rd, 2008, 05:39 PM	#21
Brandon Freeman Major Player Join Date: Feb 2007 Location: Boise, ID Posts: 226	What were the settings for the last picture you posted? I'm seeing an artifact on the out of focus light in the background there not seen in the other photos -- like you can kind of see the pin of light through the bokeh. There's documentation of this artifact elsewhere, but you seem to be avoiding it in all the other photos. Do you remember what settings you had for each photo? __________________ Canon EOS 7D, Final Cut Studio 2

January 23rd, 2008, 06:02 PM	#24
Brandon Freeman Major Player Join Date: Feb 2007 Location: Boise, ID Posts: 226	Well, I can't find the other thread, now, but YAY! I actually don't have the Letus Extreme yet (should be here soon), and this artifact was a concern for me till now. It looks like the camera iris needs to be kept fairly open, or else somehow the bokeh is slightly see through. Makes no sense to me, but it is a great relief to know how to work around it. Bummer about having to keep the camera open, though, because that means it'll be harder to focus on the ground glass (I'd think). EDIT: Keep in mind my sole form of education in all matters is trial and error -- I'm sure there is someone more "head-learned" than I who can make sense of this in a technical way. Me, I's just happy 'bout the purty pictures. :) __________________ Canon EOS 7D, Final Cut Studio 2

January 23rd, 2008, 08:51 PM	#26
Brandon Freeman Major Player Join Date: Feb 2007 Location: Boise, ID Posts: 226	Found the thread: http://www.dvinfo.net/conf/showthread.php?t=106882 __________________ Canon EOS 7D, Final Cut Studio 2

January 19th, 2008, 02:00 PM	#16
Stathis Athanasiou Regular Crew Join Date: Jun 2007 Location: Athens, Hellas Posts: 73	I haven't had time to test the difference between open and closed iris on the camera. Thinking about it, I believe it wouldn't make much of a difference changing the iris on the camera lens, as opening and closing the iris on the photographic lens itself. Because changing the camera iris doesn't change how the scene is perceived by the photo lens, which is what matters when using the Letus. But that has yet to be proven by test. (tomorrow maybe)

January 19th, 2008, 08:53 PM	#17
Oleg Kalyan Major Player Join Date: Apr 2006 Location: MOSCOW Posts: 860	Great, look forwards to your test, and appreciate your effort, we all as a community learn here!

January 21st, 2008, 04:21 AM	#19
Oleg Kalyan Major Player Join Date: Apr 2006 Location: MOSCOW Posts: 860	Thank you for your test, pictures look very sharp. Good to know you can still shoot wide open on camera, so that light loss is minimal, I mostly concerned about low light shooting, and possible light loss. The lowest f stop on camera is 1.7 did you have to zoom in more, so that it become 2.4? Thanks again. Oleg.

January 21st, 2008, 05:26 AM	#20
Stathis Athanasiou Regular Crew Join Date: Jun 2007 Location: Athens, Hellas Posts: 73	Yes, the zoom reading was 1.4m and F2.4 was the most open at this length.

January 23rd, 2008, 05:49 PM	#22
Stathis Athanasiou Regular Crew Join Date: Jun 2007 Location: Athens, Hellas Posts: 73	Brandon, if you roll over with your mouse you can see the settings for each photo.

January 23rd, 2008, 05:50 PM	#23
Stathis Athanasiou Regular Crew Join Date: Jun 2007 Location: Athens, Hellas Posts: 73	no ND F 9.5 S 1/50 I haven't noticed it until now. What is it? Is it random?

January 24th, 2008, 03:27 AM	#27
Stathis Athanasiou Regular Crew Join Date: Jun 2007 Location: Athens, Hellas Posts: 73	Thanks. From what I see from the pictures I posted, using ND and having the iris wide open, produces a sharply focused ground glass that doesn't show through. To my eyes the sharpest picture is the one with ND1/32 f2.4 S1/25