Poor resolution on telephoto - is it normal?

Leonard Levy · April 6th, 2009, 11:00 PM

Serena, Unless my lens is a fluke (which I doubt) you will probably see quite serious CA on real world shots at full telephoto where there is a lot of contrast and a bright background . I first saw it with a black clad surfer walking across the frame withy the sky behind him. He had a red line all along one side. The rest of the shot looked great, and the sky was cloudy, so not way over 100% if even that, but it was unusable.
I've also seen it on birds on the beach and other contrasty objects. I've just become wary of full telephoto.

I have not actually done careful tests to sus out when and where it occurs though. Perhaps my iris was closed beyond f8 and that had an effect. I should test it more carefully and if I get the chance I'll report here.

Serena Steuart · April 7th, 2009, 01:10 AM

That is CA, not diffraction. Haven't seen anything like that effect (I also shoot yachting events using full focal length). You had a high contrast subject, so it would show any problems.

EDIT: Just to check I took the camera outside and shot this at full focal length, f/3.4. Focussed on the power pole. There is evidence of CA on the aerial on the right; that isn't in the same plane as the power pole.

Serena Steuart · April 7th, 2009, 04:26 PM

Incidentally, diffraction limited resolution is a function of aperture diameter (not really about sharp edges) and is quite well explained here: Angular resolution - Wikipedia, the free encyclopedia

Keith Moreau · April 7th, 2009, 06:39 PM

Quote:

Originally Posted by Leonard Levy

Serena, Unless my lens is a fluke (which I doubt) you will probably see quite serious CA on real world shots at full telephoto where there is a lot of contrast and a bright background . I first saw it with a black clad surfer walking across the frame withy the sky behind him. He had a red line all along one side. The rest of the shot looked great, and the sky was cloudy, so not way over 100% if even that, but it was unusable.
I've also seen it on birds on the beach and other contrasty objects. I've just become wary of full telephoto.

I have not actually done careful tests to sus out when and where it occurs though. Perhaps my iris was closed beyond f8 and that had an effect. I should test it more carefully and if I get the chance I'll report here.

For me the way to get rid of the unusable blue fringing with birds against the sky (CA I guess or maybe some other artifact) when using extreme telephoto and cheapo Telephoto adapters was to stop way down, beyond f8 up to f16. That however resulted it very soft images, but at least usable.

Serena Steuart · April 7th, 2009, 07:50 PM

You have to be careful about clipping a colour channel, which can lead to very odd effects. Most of the chromatic aberration is contributed by the outside of the lens (off axis optical errors). Closing the aperture reduces the portion failing to bring all colours to a common focus. Similarly errors in focussing can show colour fringes (particularly in 3 sensor cameras).

Leonard Levy · April 9th, 2009, 12:04 AM

Serena -the pole on the side was the CA I 'm talking about.
If in focus it would be more noticeable and it is much worse the more off axis you are. If you were following a larger subject ( like that pole) across the frame the CA would follow it across and maybe go away in the center but might be quite noticeable off axis and might be completely unusable if it were the subject of the shot- say a bird or a surfer in a black suit walking across the frame.

Also that is not a high contrast shot. My experience is that if you had a brighter sky ( perhaps an hazy overcast day or a backlit sky) and a subject either black or in shadow the CA would be even more noticeable. I have only seen it in that kind of circumstance but it was very noticeable.
I don't remember ever seeing such bad CA in professional cameras in many previous years, though maybe I just missed it or in SD it was less noticeable.
I still love the camera though.

lenny levy

Serena Steuart · April 9th, 2009, 06:37 AM

Yes, I understand what CA is, and the signs of it in an image (as I pointed it out). What I said was that I see it near the edges but not in the central region. That particular frame grab was extracted from a clip where I panned the pole from right to left, and actually employed different gammas and detail on/off. The frame grab shows the power pole and fittings in good detail and in focus without noticeable CA, which contradicts what you've said above. So I do not see what you describe. The subject is quite high contrast (but not backlit) and the image indicates (to me) a lower mtf than I would like. Attached is a frame grab taken today, where the boat fills the frame. There are signs of CA fore and aft, but I don't see that in the majority of the frame. Now I'd like to have the image pin sharp with high MTF all over the frame, but you said "unusable" and I don't find that clip unusable or even questionable (I'd be less happy if it was my Canon 5D).
Discussions of faults or strengths are not a matter for defending a product. I don't make or sell the EX and it doesn't matter to me whether other owners like it or not. Whether or not my experience matches that of other owners is of interest to me and might be of some use to others. I've no doubt that you've accurately described the performance you're getting. I suggest getting the lens checked.

Leonard Levy · April 9th, 2009, 12:12 PM

Serena,
I'll have to check my camera more carefully.
The images I describe were not the results of tests but just some shots I took that surprised me. I'll check more carefully in the next few weeks and if I can find that shot I 'll post it.

I think it may require higher contrast and that would be a good thing as it would not be that common , but perhaps there is another explanation.

Are you used to seeing the off axis CA you've seen on the EX-1 on other professional cameras ( not baby cameras but professional cameras that I am telling clients my EX-1 can compete with.)
At least an HVX200 and higher quality. ( don't expect it to beat an F900 .)

Serena Steuart · April 21st, 2009, 11:12 PM

Here's something to think about: http://www.biox.kth.se/kjellinternet/Pinhole.pdf

Tom Hardwick · April 22nd, 2009, 01:47 AM

Thanks for the link Serena. I've had a lot of fun with my DSLR. Simply take off the lens and cover the mirror-box bayonet with some aluminium kitchen foil. Use a needle to pin-prick the centre of the foil to make your pinhole, and leave the camera exposing.

Easy and quick to enlarge the pinhole for another attempt, because finding the right size is trial and error. The bigger the chip in your DSLR the more tolerant it seems to be of pinhole size.

tom.

Steve Shovlar · April 23rd, 2009, 04:26 PM

If you are not happy with telephoto resolution you could always use the Adaptimax on an EX3 with Nikon lenses. It gives edge to edge sharpness and way better telephoto. A 200mm Nikon would give 1080mm and a 300mm Nikon would give the equivelent of 1620mm!!! You can see some footage here.
Sony PMW EX3 Nikon Adaptor.

April 7th, 2009, 01:10 AM	#17
Serena Steuart Major Player Join Date: Jun 2006 Location: Studio Alnitak, Melbourne, Victoria, Australia Posts: 640 Images: 3	That is CA, not diffraction. Haven't seen anything like that effect (I also shoot yachting events using full focal length). You had a high contrast subject, so it would show any problems. EDIT: Just to check I took the camera outside and shot this at full focal length, f/3.4. Focussed on the power pole. There is evidence of CA on the aerial on the right; that isn't in the same plane as the power pole. Attached Thumbnails Last edited by Serena Steuart; April 7th, 2009 at 02:08 AM. Reason: to attach image

April 7th, 2009, 07:50 PM	#20
Serena Steuart Major Player Join Date: Jun 2006 Location: Studio Alnitak, Melbourne, Victoria, Australia Posts: 640 Images: 3	You have to be careful about clipping a colour channel, which can lead to very odd effects. Most of the chromatic aberration is contributed by the outside of the lens (off axis optical errors). Closing the aperture reduces the portion failing to bring all colours to a common focus. Similarly errors in focussing can show colour fringes (particularly in 3 sensor cameras). Last edited by Serena Steuart; April 7th, 2009 at 08:41 PM.

April 9th, 2009, 06:37 AM	#22
Serena Steuart Major Player Join Date: Jun 2006 Location: Studio Alnitak, Melbourne, Victoria, Australia Posts: 640 Images: 3	Yes, I understand what CA is, and the signs of it in an image (as I pointed it out). What I said was that I see it near the edges but not in the central region. That particular frame grab was extracted from a clip where I panned the pole from right to left, and actually employed different gammas and detail on/off. The frame grab shows the power pole and fittings in good detail and in focus without noticeable CA, which contradicts what you've said above. So I do not see what you describe. The subject is quite high contrast (but not backlit) and the image indicates (to me) a lower mtf than I would like. Attached is a frame grab taken today, where the boat fills the frame. There are signs of CA fore and aft, but I don't see that in the majority of the frame. Now I'd like to have the image pin sharp with high MTF all over the frame, but you said "unusable" and I don't find that clip unusable or even questionable (I'd be less happy if it was my Canon 5D). Discussions of faults or strengths are not a matter for defending a product. I don't make or sell the EX and it doesn't matter to me whether other owners like it or not. Whether or not my experience matches that of other owners is of interest to me and might be of some use to others. I've no doubt that you've accurately described the performance you're getting. I suggest getting the lens checked. Attached Thumbnails

April 6th, 2009, 11:00 PM	#16
Leonard Levy Trustee Join Date: Feb 2006 Location: USA Posts: 1,684	Serena, Unless my lens is a fluke (which I doubt) you will probably see quite serious CA on real world shots at full telephoto where there is a lot of contrast and a bright background . I first saw it with a black clad surfer walking across the frame withy the sky behind him. He had a red line all along one side. The rest of the shot looked great, and the sky was cloudy, so not way over 100% if even that, but it was unusable. I've also seen it on birds on the beach and other contrasty objects. I've just become wary of full telephoto. I have not actually done careful tests to sus out when and where it occurs though. Perhaps my iris was closed beyond f8 and that had an effect. I should test it more carefully and if I get the chance I'll report here.

April 7th, 2009, 04:26 PM	#18
Serena Steuart Major Player Join Date: Jun 2006 Location: Studio Alnitak, Melbourne, Victoria, Australia Posts: 640 Images: 3	Incidentally, diffraction limited resolution is a function of aperture diameter (not really about sharp edges) and is quite well explained here: Angular resolution - Wikipedia, the free encyclopedia

April 9th, 2009, 12:04 AM	#21
Leonard Levy Trustee Join Date: Feb 2006 Location: USA Posts: 1,684	Serena -the pole on the side was the CA I 'm talking about. If in focus it would be more noticeable and it is much worse the more off axis you are. If you were following a larger subject ( like that pole) across the frame the CA would follow it across and maybe go away in the center but might be quite noticeable off axis and might be completely unusable if it were the subject of the shot- say a bird or a surfer in a black suit walking across the frame. Also that is not a high contrast shot. My experience is that if you had a brighter sky ( perhaps an hazy overcast day or a backlit sky) and a subject either black or in shadow the CA would be even more noticeable. I have only seen it in that kind of circumstance but it was very noticeable. I don't remember ever seeing such bad CA in professional cameras in many previous years, though maybe I just missed it or in SD it was less noticeable. I still love the camera though. lenny levy

April 9th, 2009, 12:12 PM	#23
Leonard Levy Trustee Join Date: Feb 2006 Location: USA Posts: 1,684	Serena, I'll have to check my camera more carefully. The images I describe were not the results of tests but just some shots I took that surprised me. I'll check more carefully in the next few weeks and if I can find that shot I 'll post it. I think it may require higher contrast and that would be a good thing as it would not be that common , but perhaps there is another explanation. Are you used to seeing the off axis CA you've seen on the EX-1 on other professional cameras ( not baby cameras but professional cameras that I am telling clients my EX-1 can compete with.) At least an HVX200 and higher quality. ( don't expect it to beat an F900 .)

April 21st, 2009, 11:12 PM	#24
Serena Steuart Major Player Join Date: Jun 2006 Location: Studio Alnitak, Melbourne, Victoria, Australia Posts: 640 Images: 3	Here's something to think about: http://www.biox.kth.se/kjellinternet/Pinhole.pdf

April 22nd, 2009, 01:47 AM	#25
Tom Hardwick Inner Circle Join Date: Mar 2003 Location: Billericay, England UK Posts: 4,711	Thanks for the link Serena. I've had a lot of fun with my DSLR. Simply take off the lens and cover the mirror-box bayonet with some aluminium kitchen foil. Use a needle to pin-prick the centre of the foil to make your pinhole, and leave the camera exposing. Easy and quick to enlarge the pinhole for another attempt, because finding the right size is trial and error. The bigger the chip in your DSLR the more tolerant it seems to be of pinhole size. tom.

April 23rd, 2009, 04:26 PM	#26
Steve Shovlar Major Player Join Date: Feb 2005 Location: Dorset UK Posts: 697	If you are not happy with telephoto resolution you could always use the Adaptimax on an EX3 with Nikon lenses. It gives edge to edge sharpness and way better telephoto. A 200mm Nikon would give 1080mm and a 300mm Nikon would give the equivelent of 1620mm!!! You can see some footage here. Sony PMW EX3 Nikon Adaptor.