How to Read MTF chart?


sfoto100

Senior Member
Nov 29, 2009
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#2

ovaltinemilo

Senior Member
Sep 12, 2009
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Sin jia Po lah
#3
it shows sharpness from center to a distance away from center of lens...measured at different spatial frequency(different colours)...dotted lines tell something too...

Help you get started with your investigation...:)
 

jsprtan

New Member
May 12, 2010
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#4
Help you get started with your investigation...:)
:bsmilie: I shall also give my 2 cents..

The 2 different colour line are for 2 different aperature. one wide open and the other is for f8.0.
 

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ovaltinemilo

Senior Member
Sep 12, 2009
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#5
:bsmilie: I shall also give my 2 cents..

The 2 different colour line are for 2 different aperature. one wide open and the other is for f8.0.
actually, we should read legend to confirm:)
the chart tells a lens at wide open.

http://www.sigmaphoto.com/pu-mtf-chart-guide
 

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knpan

Senior Member
May 2, 2006
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#7
Quote from website :
The readings at 10 lines per millimeter measure the lens's contrast ability (red lines), repeating fine parallel lines spaced at 30 lines per millimeter measure the lens' sharpness ability (green lines), when the aperture is wide open.

Fine repeating line sets are created parallel to a diagonal line running from corner to corner of the frame, are called Sagittal lines (S)

Bros, able to elaborate the red ones i highlighted?

jsprtan also said 1 of the line is F8, the website did not state F8 . . :dunno:

What is image height from 0 to 20mm ?

So as website says 1 is the higest value for contrast, does the Y axis ( Vertical line) show for sharpness too ?
 

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knpan

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May 2, 2006
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#9
O so different companies have different style, meaning etc on MTF charts?
 

Aug 3, 2008
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Hougang
www.geekbrains.com
#10
Hey dude, the link that jsprtan has provided from luminous landscape explains it all. Sharpness is based on the resolving power and it's inseparable from the contrast. I couldn't find any legend for the Sigma MTF though.

PS: Most of the times, the manufacturer's MTF do not translate to actual field performance of the lens as MTF doesn't capture lens flaring issues, coma noise, vignetting, aberrations etc
 

henry soh

New Member
Aug 29, 2008
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#11
Hi, MFT chart has a line pairs with a dotted line. They should be as close together as possible and higher from the y-axis and move straight as far as possible and not dipping down. All these go to indicate how sharp the lens is. This is only theory. Practically, the lens should be tested wide open and checked on the camera's LCD screen by zooming in 8x and scrolling to see
whether the sharpness at centre and corners are the same or otherwise. If there is a difference, then the lens is not an L lens e.g.24-105mm canon. Stopping down the lens means that only light from the central axis is being used to capture the image and not the overall light from the lens.
 

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