Chromatic aberration

Sean Donnelly · April 20th, 2008, 07:29 AM

Yes. It's visible on a 17" monitor. The question of whether or not it is objectionable is an aesthetic question, and depends on many factors. I really do think it's inherent in the design, and that will happen with any affordable anamorphic converter. The iscorama also basically has a variable distance proxar as a focusing element, which may cause some aberration as well as not being designed for digital use, especially HD.

Mark David Williams · April 20th, 2008, 07:42 AM

OK so using it with my EX-1 is going to leave visible and in my opinion unpleasant artifacts. But I could use it with my standard 16mm camera to achieve a widescreen look? Probably free from this problem.

Tom Hardwick · April 20th, 2008, 07:50 AM

Paul - an anamorphic lens is a wide-angle converter but in one plane only, and isn't designed for any particular aspect ratio gate or chip. Turning it off the normal horizontal axis won't affect the CA in the slightest.

Mark - you ask if the colour bleed is such big problem that it would be noticeable on a large screen. The answer has to be yes if your films are yawn-a-mile boring, but no for any other production. If your clients are reduced to looking at the frame corners and whispering to their neighbours that resolution is down somewhat and vignetting is beginning to be a problem, then you've lost it as a filmmaker.

I'm pretty sure you're not amongst this group, so don't lose sleep over the edge definition. It's like that with my Aspheron on the Z1. It takes that lens's wide-angle equivalent of 32 mm down to a visually striking 17 mm, and with zero barrel distortion that's a strikingly powerful focal length.

There are losses to be had, for sure. But the gains in dof and perspective distortion control far outweigh the technical losses, I assure you.

tom.

Mark David Williams · April 20th, 2008, 07:59 AM

Tom Thank you. One more thing How in your opinion and if at all would this aberration affect chroma keying? and other FX work!

Tom Hardwick · April 20th, 2008, 08:09 AM

Good question. I'd say 'adversely'.

Mark David Williams · April 20th, 2008, 08:14 AM

I have tried to use the letus with a pentax lens and then the Anamorphic adapter. I cant seem to get good focus with this arrangement do you think if I bought the EX-1 Letus updated lens it may solve all problems? including the colour bleed?

Tom Hardwick · April 20th, 2008, 08:28 AM

You asking me Mark? The answer is I don't know, and no-one will know till they test it scientifically and carefully.

Thing is, anything you fit in front of your front element will degrade the image. From a UV filter to a wide-converter to an anamorphic to a grad to a Letus to a spinning disc to a prism, microscope, monocular of the double-glazed bus windows.

But if all or any of these things enable us to get the shot, then the loss of resolution has been worth it. Oh yes. It's a bit like Mercalli image stabilisation - you lose resolution but gain screen-cred.

tom.

Mark David Williams · April 20th, 2008, 08:43 AM

Tom Yes I agree. Would need to do tests. But possibly more money that may go nowwhere. Its my Birthday today and I have some cash. Choices? I have an old adobe premier I could upgrade to get the old serious magics On location program. Buy a cheap jib OR go for Hiens EX-1 achromat upgrade. Some have said Hiens new achromat loses more light? Swings and roundabouts? I think the likeliehood is Im not going to get rid of the chromatic aberration and just stick with it as is. Do I need to gain a little extra sharpness with Hiens new lens at the expense of light? As for the cheap jib? On location could be looking good!.

Sean Donnelly · April 20th, 2008, 09:08 AM

That sounds like a lot of glass involved, which is going to create lots of problems with maximum sharpness, and using a letus will never be as sharp as just the stock lens (that's one thing I like about it so much). I don't think you're going to get anamorphic without some kind of CA or other degradation for less than $100k, so follow Tom's advice and go for something that's going to really improve your shots.

Mark David Williams · April 20th, 2008, 09:12 AM

Quote:

Originally Posted by Sean Donnelly

That sounds like a lot of glass involved, which is going to create lots of problems with maximum sharpness, and using a letus will never be as sharp as just the stock lens (that's one thing I like about it so much). I don't think you're going to get anamorphic without some kind of CA or other degradation for less than $100k, so follow Tom's advice and go for something that's going to really improve your shots.

Sean my thinking was not about sharpness so much as the chromatic aberration

Sean Donnelly · April 20th, 2008, 09:23 AM

That definitely can come from a complex optical path as well. The achromat helps with uniform sharpness, but won't solve any CA problems. It'd be interesting to see a comparison between the iscorama and the standard lens cropped to 2.35 and scaled up.

Paul Curtis · April 20th, 2008, 12:56 PM

Quote:

Originally Posted by Tom Hardwick

Paul - an anamorphic lens is a wide-angle converter but in one plane only, and isn't designed for any particular aspect ratio gate or chip. Turning it off the normal horizontal axis won't affect the CA in the slightest.

Tom, okay i understand that. I would like to see a full 1920 x 1080 frame that has been squeezed via this adaptor? Mark is that possible? The ones shown are all cropped down and might as well have come from a crop of a normal HD frame. Im curious as to the quality of this adaptor with a full res frame and the EX1 at its widest setting.

cheers
paul

Mark David Williams · April 20th, 2008, 01:45 PM

Quote:

Originally Posted by Paul Curtis

Tom, okay i understand that. I would like to see a full 1920 x 1080 frame that has been squeezed via this adaptor? Mark is that possible? The ones shown are all cropped down and might as well have come from a crop of a normal HD frame. Im curious as to the quality of this adaptor with a full res frame and the EX1 at its widest setting.

cheers
paul

Hi Paul

Did you download the last picture I put up?

It shows 2797x1080?

Paul Curtis · April 21st, 2008, 02:20 AM

Quote:

Originally Posted by Mark David Williams

Hi Paul

Did you download the last picture I put up?

It shows 2797x1080?

Oops, no i didn't. Have now though.

I think the CA renders the image unusable (imho). If you're looking for a wider fov then perhaps a dedicated sony wide angle adaptor (which is designed specifically for the EX1 lens) and crop down. If you're looking for resolution then i'd try scaling with one of those intelligent scalers (like the instant HD ones) but i think the resolution is a minor point.

Or a 35mm adaptor with wide lenses.

Or just step back a long way :)

cheers
paul

Mark David Williams · April 21st, 2008, 05:27 AM

OK Today I took the whole thing outside. Set up a HD ready monitor and not full defination. Attached the letus with a pentax lens and then the anamorphic lens. I have added some colour correction of my own.

http://www.freewebs.com/markwilliams/Mark1.png

http://www.freewebs.com/markwilliams/Mark2.png

A few conclusions for me at least and with this setup. I cant trust the cameras LCD and histogram and getting focus right is very difficult. I now want a 1920 monitor.

April 20th, 2008, 07:29 AM	#31
Sean Donnelly Regular Crew Join Date: Jan 2008 Location: New York, NY Posts: 188	Yes. It's visible on a 17" monitor. The question of whether or not it is objectionable is an aesthetic question, and depends on many factors. I really do think it's inherent in the design, and that will happen with any affordable anamorphic converter. The iscorama also basically has a variable distance proxar as a focusing element, which may cause some aberration as well as not being designed for digital use, especially HD.

April 20th, 2008, 07:42 AM	#32
Mark David Williams Major Player Join Date: Dec 2007 Location: Hertfordshire UK Posts: 414	OK so using it with my EX-1 is going to leave visible and in my opinion unpleasant artifacts. But I could use it with my standard 16mm camera to achieve a widescreen look? Probably free from this problem.

April 20th, 2008, 07:50 AM	#33
Tom Hardwick Inner Circle Join Date: Mar 2003 Location: Billericay, England UK Posts: 4,711	Paul - an anamorphic lens is a wide-angle converter but in one plane only, and isn't designed for any particular aspect ratio gate or chip. Turning it off the normal horizontal axis won't affect the CA in the slightest. Mark - you ask if the colour bleed is such big problem that it would be noticeable on a large screen. The answer has to be yes if your films are yawn-a-mile boring, but no for any other production. If your clients are reduced to looking at the frame corners and whispering to their neighbours that resolution is down somewhat and vignetting is beginning to be a problem, then you've lost it as a filmmaker. I'm pretty sure you're not amongst this group, so don't lose sleep over the edge definition. It's like that with my Aspheron on the Z1. It takes that lens's wide-angle equivalent of 32 mm down to a visually striking 17 mm, and with zero barrel distortion that's a strikingly powerful focal length. There are losses to be had, for sure. But the gains in dof and perspective distortion control far outweigh the technical losses, I assure you. tom.

April 20th, 2008, 07:59 AM	#34
Mark David Williams Major Player Join Date: Dec 2007 Location: Hertfordshire UK Posts: 414	Tom Thank you. One more thing How in your opinion and if at all would this aberration affect chroma keying? and other FX work!

April 20th, 2008, 08:09 AM	#35
Tom Hardwick Inner Circle Join Date: Mar 2003 Location: Billericay, England UK Posts: 4,711	Good question. I'd say 'adversely'.

April 20th, 2008, 08:14 AM	#36
Mark David Williams Major Player Join Date: Dec 2007 Location: Hertfordshire UK Posts: 414	I have tried to use the letus with a pentax lens and then the Anamorphic adapter. I cant seem to get good focus with this arrangement do you think if I bought the EX-1 Letus updated lens it may solve all problems? including the colour bleed?

April 20th, 2008, 08:28 AM	#37
Tom Hardwick Inner Circle Join Date: Mar 2003 Location: Billericay, England UK Posts: 4,711	You asking me Mark? The answer is I don't know, and no-one will know till they test it scientifically and carefully. Thing is, anything you fit in front of your front element will degrade the image. From a UV filter to a wide-converter to an anamorphic to a grad to a Letus to a spinning disc to a prism, microscope, monocular of the double-glazed bus windows. But if all or any of these things enable us to get the shot, then the loss of resolution has been worth it. Oh yes. It's a bit like Mercalli image stabilisation - you lose resolution but gain screen-cred. tom.

April 20th, 2008, 08:43 AM	#38
Mark David Williams Major Player Join Date: Dec 2007 Location: Hertfordshire UK Posts: 414	Tom Yes I agree. Would need to do tests. But possibly more money that may go nowwhere. Its my Birthday today and I have some cash. Choices? I have an old adobe premier I could upgrade to get the old serious magics On location program. Buy a cheap jib OR go for Hiens EX-1 achromat upgrade. Some have said Hiens new achromat loses more light? Swings and roundabouts? I think the likeliehood is Im not going to get rid of the chromatic aberration and just stick with it as is. Do I need to gain a little extra sharpness with Hiens new lens at the expense of light? As for the cheap jib? On location could be looking good!.

April 20th, 2008, 09:08 AM	#39
Sean Donnelly Regular Crew Join Date: Jan 2008 Location: New York, NY Posts: 188	That sounds like a lot of glass involved, which is going to create lots of problems with maximum sharpness, and using a letus will never be as sharp as just the stock lens (that's one thing I like about it so much). I don't think you're going to get anamorphic without some kind of CA or other degradation for less than $100k, so follow Tom's advice and go for something that's going to really improve your shots.

April 20th, 2008, 09:23 AM	#41
Sean Donnelly Regular Crew Join Date: Jan 2008 Location: New York, NY Posts: 188	That definitely can come from a complex optical path as well. The achromat helps with uniform sharpness, but won't solve any CA problems. It'd be interesting to see a comparison between the iscorama and the standard lens cropped to 2.35 and scaled up.

April 21st, 2008, 05:27 AM	#45
Mark David Williams Major Player Join Date: Dec 2007 Location: Hertfordshire UK Posts: 414	OK Today I took the whole thing outside. Set up a HD ready monitor and not full defination. Attached the letus with a pentax lens and then the anamorphic lens. I have added some colour correction of my own. http://www.freewebs.com/markwilliams/Mark1.png http://www.freewebs.com/markwilliams/Mark2.png A few conclusions for me at least and with this setup. I cant trust the cameras LCD and histogram and getting focus right is very difficult. I now want a 1920 monitor.