Comments on: Have You Seen My Acutance? http://www.lensrentals.com/blog/2009/06/have-you-seen-my-acutance Photo/video thoughts from the largest rental house Tue, 21 May 2013 21:28:18 +0000 hourly 1 http://wordpress.org/?v=3.3.2 By: Eugene http://www.lensrentals.com/blog/2009/06/have-you-seen-my-acutance/comment-page-1#comment-36279 Eugene Fri, 29 Mar 2013 19:02:57 +0000 http://localhost:6081/news/2009.06.13/have-you-seen-my-acutance#comment-36279 I'm wondering how easy would it be to see MTF differences in your photographs. As I understand, digital cameras first blur the image (to prevent aliasing), and then sharpen it in post-processing. So if you look at the RAW image with no sharpness enhancement, then everything will look blurry. If you look at sharpened RAW images (which is what most people use), then differences in acutance might have been removed by the sharpening process. So how do you properly test your lens for sharpness? I’m wondering how easy would it be to see MTF differences in your photographs. As I understand, digital cameras first blur the image (to prevent aliasing), and then sharpen it in post-processing. So if you look at the RAW image with no sharpness enhancement, then everything will look blurry. If you look at sharpened RAW images (which is what most people use), then differences in acutance might have been removed by the sharpening process. So how do you properly test your lens for sharpness?

]]> By: Anthony http://www.lensrentals.com/blog/2009/06/have-you-seen-my-acutance/comment-page-1#comment-32504 Anthony Mon, 11 Mar 2013 22:02:05 +0000 http://localhost:6081/news/2009.06.13/have-you-seen-my-acutance#comment-32504 Roger, I was wondering if there's any easy way to relatively convert between the MTF50 numbers you typically post in your articles, and the values in the MTF charts that the manufacturers provide? I tried posting elsewhere on a forum and got a 1200+ word essay "answer" on how Canon's MTF charts are done (included mention of Airy Discs and comments asking if I know how to read an MTF chart or not. The general gist I've gotten is that either they're two different systems and I shouldn't be trying to compare them, or I don't want to know the math involved. Thanks, Anthony Roger,

I was wondering if there’s any easy way to relatively convert between the MTF50 numbers you typically post in your articles, and the values in the MTF charts that the manufacturers provide? I tried posting elsewhere on a forum and got a 1200+ word essay “answer” on how Canon’s MTF charts are done (included mention of Airy Discs and comments asking if I know how to read an MTF chart or not. The general gist I’ve gotten is that either they’re two different systems and I shouldn’t be trying to compare them, or I don’t want to know the math involved.

Thanks,
Anthony

]]> By: Feng Chun http://www.lensrentals.com/blog/2009/06/have-you-seen-my-acutance/comment-page-1#comment-25763 Feng Chun Wed, 12 Dec 2012 08:11:21 +0000 http://localhost:6081/news/2009.06.13/have-you-seen-my-acutance#comment-25763 This is really a great post on MTF chart. I have found your site from a forum and read your blog from 2012 till now. Really enjoyed it. This is really a great post on MTF chart.

I have found your site from a forum and read your blog from 2012 till now. Really enjoyed it.

]]> By: Roger Cicala http://www.lensrentals.com/blog/2009/06/have-you-seen-my-acutance/comment-page-1#comment-24503 Roger Cicala Tue, 06 Nov 2012 14:33:07 +0000 http://localhost:6081/news/2009.06.13/have-you-seen-my-acutance#comment-24503 Phil, I think that's an excellent tool that SLR Gear has. Very intuitive. Blur index is proprietary, so we can't know exactly what it measures (although some people say they've reverse engineered it) but it still gives a great comparison tool. We have the wide end MTF chart for the 70mm: https://www.lensrentals.com/rent/canon/lenses/telephoto/canon-70-300mm-f4-5.6-is and 15-85:https://www.lensrentals.com/rent/canon/lenses/normal-range/canon-ef-s-15-85mm-f3.5-5.6-is-usm but I don't have the telephoto end anymore. Not sure where they've gone. But you can usually find them at the Canon Museum EOS section. Roger Phil,

I think that’s an excellent tool that SLR Gear has. Very intuitive. Blur index is proprietary, so we can’t know exactly what it measures (although some people say they’ve reverse engineered it) but it still gives a great comparison tool.

We have the wide end MTF chart for the 70mm: https://www.lensrentals.com/rent/canon/lenses/telephoto/canon-70-300mm-f4-5.6-is and 15-85:https://www.lensrentals.com/rent/canon/lenses/normal-range/canon-ef-s-15-85mm-f3.5-5.6-is-usm but I don’t have the telephoto end anymore. Not sure where they’ve gone. But you can usually find them at the Canon Museum EOS section.

Roger

]]> By: Phil Olenick http://www.lensrentals.com/blog/2009/06/have-you-seen-my-acutance/comment-page-1#comment-24502 Phil Olenick Tue, 06 Nov 2012 14:14:58 +0000 http://localhost:6081/news/2009.06.13/have-you-seen-my-acutance#comment-24502 Brilliantly clear piece. I went looking for MTF charts for my Canon lenses, couldn't find one for my new EF-S 15-85, which I got before opting for the new EF-S 18-135 STM "movie zoom" kitted with my new crop sensor EOS T4i (called the 650D, I believe, in most of the world) - trying to decide if the 18-135 is as sharp as the 15-85. Before getting those this summer, I've done most of my shooting with the f/2.8 17-55 on an XTi (400D), which is beautifully sharp wide open - I hardly ever stopped it down. I traded in my original EF-S 17-85 and lots of additional moolah for the 17-55, which was well worth it. I've found Canon's MTF charts for all of those except the 15-85. Any leads to finding those charts? I'd also like to find the charts for the standard (not the DO) EF 70-300, which I also consider to be a very good lens. Before finding this piece, my main source for evaluating lenses has been the interactive blur level charts at http://slrgear.com/reviews/showcat.php/cat/2, which show "blur" levels across the frame at different apertures and focal lengths as a color-coded surface with sliders for the two factors. (You have to click on the static image to bring up the interactive version.) I'd be interested in your reaction to that tool. Brilliantly clear piece. I went looking for MTF charts for my Canon lenses, couldn’t find one for my new EF-S 15-85, which I got before opting for the new EF-S 18-135 STM “movie zoom” kitted with my new crop sensor EOS T4i (called the 650D, I believe, in most of the world) – trying to decide if the 18-135 is as sharp as the 15-85.

Before getting those this summer, I’ve done most of my shooting with the f/2.8 17-55 on an XTi (400D), which is beautifully sharp wide open – I hardly ever stopped it down. I traded in my original EF-S 17-85 and lots of additional moolah for the 17-55, which was well worth it.

I’ve found Canon’s MTF charts for all of those except the 15-85. Any leads to finding those charts? I’d also like to find the charts for the standard (not the DO) EF 70-300, which I also consider to be a very good lens.

Before finding this piece, my main source for evaluating lenses has been the interactive blur level charts at http://slrgear.com/reviews/showcat.php/cat/2, which show “blur” levels across the frame at different apertures and focal lengths as a color-coded surface with sliders for the two factors. (You have to click on the static image to bring up the interactive version.) I’d be interested in your reaction to that tool.

]]> By: RP http://www.lensrentals.com/blog/2009/06/have-you-seen-my-acutance/comment-page-1#comment-17132 RP Fri, 24 Aug 2012 01:21:42 +0000 http://localhost:6081/news/2009.06.13/have-you-seen-my-acutance#comment-17132 Roger, Why Canon shows 2 continuous blue and black lines at wide and tele? What do they mean? Thick blue is f/8 at 28mm and thin blue what is it? Roger,

Why Canon shows 2 continuous blue and black lines at wide and tele? What do they mean? Thick blue is f/8 at 28mm and thin blue what is it?

]]> By: Andy http://www.lensrentals.com/blog/2009/06/have-you-seen-my-acutance/comment-page-1#comment-14897 Andy Sat, 21 Jul 2012 18:14:53 +0000 http://localhost:6081/news/2009.06.13/have-you-seen-my-acutance#comment-14897 Thanks for this article! Very well written, very informative. Thanks for this article! Very well written, very informative.

]]> By: Maji http://www.lensrentals.com/blog/2009/06/have-you-seen-my-acutance/comment-page-1#comment-7204 Maji Wed, 25 Apr 2012 19:10:54 +0000 http://localhost:6081/news/2009.06.13/have-you-seen-my-acutance#comment-7204 Thank you for the great explanation. Very informative and well presented article of an extremely complicated subject. Thank you for the great explanation. Very informative and well presented article of an extremely complicated subject.

]]> By: Freddie Parker http://www.lensrentals.com/blog/2009/06/have-you-seen-my-acutance/comment-page-1#comment-3733 Freddie Parker Thu, 08 Mar 2012 08:15:18 +0000 http://localhost:6081/news/2009.06.13/have-you-seen-my-acutance#comment-3733 Thanks, I now have a clearer understanding of the MTF charts. Will now go and check my lenses. Thanks, I now have a clearer understanding of the MTF charts. Will now go and check my lenses.

]]> By: Roger Cicala http://www.lensrentals.com/blog/2009/06/have-you-seen-my-acutance/comment-page-1#comment-3632 Roger Cicala Tue, 28 Feb 2012 22:01:58 +0000 http://localhost:6081/news/2009.06.13/have-you-seen-my-acutance#comment-3632 Larry, I must be missing something - I couldn't find a question from Matt? Larry, I must be missing something – I couldn’t find a question from Matt?

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