how to read Canon MTF chart

[gordeaux]

I'm studying the optics of several of the lenses on Canon's web site. They have an MTF chart for most of the lenses. I've read the description of how to read an MTF chart, but I can't figure out what all the lines are for, though.

There are black and blue lines. There are solid and broken lines (looks like in pairs). Total of 8 lines (4 pairs).

Does anyone know what the 8 lines are showing me & which is which? :?

[Kevin M]

Of immediate concern are the unbroken lines. Black for wide open and blue for stopped down to F8. The thick lines represent contrast and the thin lines represent resolving of fine detail. The dashed lines refer to bokeh etc - if you are concerned.

The higher up the chart the lines are and the closer together with the least fall off to the right (edge/corner performance) the better the optical quality of the lens.

You should be aware that most mtf charts are shown for full frame cameras - but if you are using a 10d which crops at 1.6 you are only concerned with performance to 13 on the horizontal scale. Thus a lens which has a mediocre chart at the edges at full frame may be quite respectable on 1.6 crop camera.



http://homepage.eircom.net/~bot/paint/10d-img/mtf.gif

[PaulB]

My copy of EF Lens Work 3 gives the following information for reading the Canon MTF charts.

The thick lines refer to a spatial frequency of 10 lines/mm
The thin lines refer to a spatial frequency of 30 lines/mm
The solid lines refer to S curves
The dotted lines refer to M curves
Black lines refer to maximum aperture
Blue lines refer to f8
The more the S and M curves are in line the more natural the blurred image becomes.

An MTF of 0.8 or more at 10 lines/mm indicates a superior lens.
An MTF of 0.6 or more at 10 lines/mm indicates a satisfactory image.

Note that the Canon MTF curves are computed for each lens and are not readings taken from an actual lens. This means that it may not be possible to directly compare the Canon figures with MTF charts published by reviewers or other manufacturers

[bosmankb]

I just downloaded Zeiss's detailed info about it and i cant bring myself to read it lol.

[Higgs Boson]

in laymans terms:

the higher for longer the better.

[bosmankb]

in laymans terms:

the higher for longer the better.

That dd not clear things up the way you worded that. I think i get the gist just thought i might like to know more about all the dashed lines. Turns out i don't. The only L lens i dont have is the Canon 15mm fisheye, else every lens is pure gold!

[Higgs Boson]

That dd not clear things up the way you worded that. I think i get the gist just thought i might like to know more about all the dashed lines. Turns out i don't. The only L lens i dont have is the Canon 15mm fisheye, else every lens is pure gold!

we have a surprisingly similar gear list.....my 24-70 is getting sold tomorrow and I plan to pick up the 15 soon as well as a 2xiii....weird. I also want the 500Lii....need another job for that one though....

[bosmankb]

:pwe have a surprisingly similar gear list.....my 24-70 is getting sold tomorrow and I plan to pick up the 15 soon as well as a 2xiii....weird. I also want the 500Lii....need another job for that one though....
Do you grab the 100 macro for portraits or is it more for specialty for you? Yes we do have a similar profile.
I have owned and sole the 85 1.2 l VI, 35 1.4L, 135 L. Sold them all over time. 85 is the only one i miss and hate at the same time. The others don't have avantages over my other lenses.

[Higgs Boson]

I also used to have the 135l and 35L but not the 85.

I do use the macro for portraits sometimes for sure, it kind of depends what's on my camera already and the situation and I don't want to lug around the 70-200.....

[Gregg.Siam]

Kind of related...there's an app for the iphone called CanonSGlens (SG is for Singapore) which has every Canon lens and the MTF chart. You can also compare lenses, compare MTF charts, FOV simulator, depth of field calculator, specs for each lens.