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06/07/2005 11:10:09 PM · #1 |
Can anyone please provide a simple explanation as to how to read MTF charts, and what they tell you. (for anyone who doesnt know what a mtf chart is look here for example //consumer.usa.canon.com/ir/controller?act=ModelDetailAct&fcategoryid=149&modelid=10512)
thanks in advance!
Message edited by author 2005-06-07 23:10:48.
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06/09/2005 12:05:51 PM · #2 |
Goto //www.google.com and enter 'MTF' and Chart' in the little white box in the middle of the screen.
Then click the little button called 'I'm feeling lucky'. Even if you aren't.
That's what I would do before posting a question.
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06/09/2005 12:32:10 PM · #3 |
Originally posted by Tom_Robbrecht:
Goto //www.google.com and enter 'MTF' and Chart' in the little white box in the middle of the screen. Then click the little button called 'I'm feeling lucky'. Even if you aren't. That's what I would do before posting a question. |
I think what you meant was:
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06/09/2005 01:09:32 PM · #4 |
The result is a Mitsubishi Japanese Stock Exhange Rate Chart...
Kudos for the advice....and baseless ego. Sorry, this site/forum is much more useful than Google.com on photography matters. Sure you can find it via google.com but that doesn't mean you'll be able to easily find something that isn't too technical and often (particularly with a short three letter common acronym like MTF) you'll get so many unrelated superflous links.
//finance.yahoo.com/q/bc?s=MTF
Nico, sorry...i don't have an answer for you. But I just thought said person's advice was rude. Hope they never ask a question on the forum.
Message edited by author 2005-06-09 13:10:20.
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06/09/2005 01:12:12 PM · #5 |
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06/09/2005 01:13:04 PM · #6 |
Originally posted by nico_blue:
Can anyone please provide a simple explanation as to how to read MTF charts, and what they tell you. |
Sorry that I don't have an answer for you, although I'm now curious about what that means myself after seeing your link.
Sorry also that people feel its necessary to bash someone for asking a legitimate photography question in a photography forum... |
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06/09/2005 01:15:55 PM · #7 |
I found this article by tweaking the suggested search to include 'lens'. As indicated if you don't know enough you can waste plenty of time slogging through unrelated information. This article may not have what you need either.
Sorry, I have no knowledge of how to read these charts and will be perusing this article myself to see if it makes any sense.
//fotogenetic.dearingfilm.com/how_to_choose_a_lens.html
Message edited by author 2005-06-09 13:32:27. |
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06/09/2005 01:21:15 PM · #8 |
MTF charts (short for Modulation Transfer Function) provide a graph analyzing a lens’ ability to resolve sharp details in very fine sets of parallel lines, and a lens’ contrast or ability to provide a sharp transfer between light and dark areas in sets of thicker parallel lines. Fine repeating line sets are created parallel to a diagonal line running from corner to corner of the 35mm frame, directly through the exact center of the image area. These are called sagittal lines, sometimes designated “S” on Canon’s MTF charts. At a 90° angle to these, additional sets of repeating lines are drawn, called Meridional (or “M”) line sets. Repeating extremely fine short parallel lines spaced at 30 lines per millimeter measure the lens’ ability to record fine details, or its resolution.
Even more important in the eyes of many optical designers is the lens’ contrast capability, which is measured with thicker sets of parallel repeating lines drawn at 10 lines per millimeter. At first glance, it would appear that any good lens would record lines running parallel to a diagonal drawn across the film with the same accuracy as lines drawn perpendicular to them. However, in real-world testing, this is often not the case. Especially in the Meridional direction, faithful reproduction of fine line sets becomes increasingly difficult as you move away from the center of the image toward one of the corners. And it’s a fact that almost all lenses produce sharper results in general near the center of the frame than at the outer edges.
MTF charts display the lens’ performance from center to corner. Running along the chart’s horizontal axis, labeled 0 to over 20, is the distance from the dead center (“0”) of a 35mm image along a diagonal line to the corner of the frame, which is about 21.5mm away. On the chart’s vertical axis is a scale representing the degree of accuracy with which the fine and coarse line sets are reproduced, in both the sagittal (parallel to the diagonal of the film format) and meridonal directions. Solid lines on the MTF charts indicate the performance of sagittal lines (parallel to the diagonal of the film), dashed lines are for the perpendicular meridional test target lines.
In theory, a perfect lens would produce nothing but straight horizontal lines across the very top of an MTF chart, indicating 100% accurate reproduction from the center of the picture (toward the left of the chart) to its outermost corners (at the right side of the chart). Of course, no such thing as a perfect lens exists from any SLR manufacturer, so MTF charts typically show lines that tend to curve downward as they move left to right (tracking the lens’ performance from center to corner of the frame).
Canon’s MTF charts give results at two apertures: wide-open, and stopped down to f/8, with the lens set to infinity focus. While MTF charts don’t include many factors that can be important when selecting a lens (size, cost, handling, closest focusing distances, AF speed, linear distortion, evenness of illumination, and of course features like Image Stabilization which may produce superior real-world results), they can indicate to the knowledgeable reviewer some of the optical characteristics they can expect from a particular lens.
Quoted from Canon: link to glossary
Message edited by muckpond - added link. |
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06/09/2005 01:23:10 PM · #9 |
BTW, it was the first link if you google
'canon mtf chart'
'how to read mtf chart'
'canon mtf'
'mtf chart lens'
Etc.
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06/09/2005 02:48:49 PM · #10 |
Very nice attempt at an apology, I must say...
Originally posted by mavrik:
BTW, it was the first link if you google
'canon mtf chart'
'how to read mtf chart'
'canon mtf'
'mtf chart lens'
Etc. |
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06/09/2005 03:21:27 PM · #11 |
Originally posted by alansfreed:
Originally posted by nico_blue:
Can anyone please provide a simple explanation as to how to read MTF charts, and what they tell you. |
Sorry also that people feel its necessary to bash someone for asking a legitimate photography question in a photography forum... |
I was thinking the same thing :/
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06/09/2005 03:40:53 PM · #12 |
If you go to the Sigma site, every lens's profile page has a MTF chart, and just beneath it is a link labelled MTF chart guide that opnes a window with a brief explanation. Here's alink to one of their macros: APO MACRO 180mm F3.5 EX IF HSM
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10/21/2008 03:49:11 PM · #13 |
I was gonna start another thread, but found this thread instead.
I am surprised Canon do not explain their MTF charts on the lens webpages. The axes in the charts are not even named (for what they represent)!!! So even if one assumes the horizontal axis is for image size (mm) and the vertical for the measured response, there is no way to tell which line represents what spatial frequency. If I *guess* again, the higher a line runs on the chart, the lower frequency it represents.. as it is relatively easy to resove lower frequency patterns.
Sigma's lens pages are much better in this regard. They at least have the axes marked, and also have a legend explaining which lines represent what spatial frequency in the test image.
Am I the only one to notice this, or do Canon always leave the charts up for guessing? |
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10/10/2010 10:26:26 AM · #14 |
| lol, i did google it. and it lead me to this forum where a bunch of bashers are telling someone to go somewhere else. in a photography forum no less. |
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10/10/2010 11:08:19 AM · #15 |
Originally posted by kanombpang:
lol, i did google it. and it lead me to this forum where a bunch of bashers are telling someone to go somewhere else. in a photography forum no less. |
LOL Classic internet. rofl |
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10/10/2010 11:50:00 AM · #16 |
Originally posted by kanombpang:
lol, i did google it. and it lead me to this forum where a bunch of bashers are telling someone to go somewhere else. in a photography forum no less. |
this was 5 years ago - time to let it go I feel. ;) |
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10/10/2010 12:59:41 PM · #17 |
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