Canon MTF charts, meaning of blue-gray?

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Bill Tuthill - 25 Aug 2005 17:54 GMT

In Canon's MTF charts, what do the blue, black and gray lines indicate?
I have no experience reading them, but kinda understand Photodo.

Presumably solid lines show saggital MTF and dotted lines show tangential.

Thanks in advance.

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David Littlewood - 25 Aug 2005 20:42 GMT

In article <430df7c2@news.meer.net>, Bill Tuthill <can@spam.co> writes

>In Canon's MTF charts, what do the blue, black and gray lines indicate?
>I have no experience reading them, but kinda understand Photodo.

In the "EF Lens Work" book, black is MTF at maximum aperture for the
lens, blue at f/8. Thick black/blue line is MTF at 10 lines/mm, thin
line at 30 lines/mm.

>Presumably solid lines show saggital MTF and dotted lines show tangential.

Yes.

I can't be sure that the same protocol is followed in whatever you are
looking at, but it seems likely there would be some consistency. I
imagine that the grey lines you see may be the thin black ones. You may
be able to deduce this from the curves!

David

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David Littlewood

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Bart van der Wolf - 25 Aug 2005 21:47 GMT

> In Canon's MTF charts, what do the blue, black and gray lines
> indicate?

See MTF chart How to read at:
<http://consumer.usa.canon.com/ir/controller?act=GlossaryAct&fcategoryid=216&alpha=MNO>

Bart

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Stephen M. Dunn - 26 Aug 2005 03:30 GMT

$In Canon's MTF charts, what do the blue, black and gray lines indicate?

Blue is f/8; black is wide open. Thick is 10 lp/mm; thin is 30.
Sometimes they use gray rather than thin black.

$Presumably solid lines show saggital MTF and dotted lines show tangential.

Yup.

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Bill Tuthill - 26 Aug 2005 17:42 GMT

> Blue is f/8; black is wide open. Thick is 10 lp/mm; thin is 30.
> Sometimes they use gray rather than thin black.

Thanks all, especially Bart for the glossary definition.

I notice some lenses do not have MTF charts on the Canon website.

Using a statistically insignificant sample size (2) I noted that the
10-22 EFS and 17-85 EFS do not have charts. Perhaps not coincidentally,
these are two lenses that everybody says are overpriced.

Why do some lenses not have MTF charts posted? The 18-55 EFS does,
and that's not an L lens. Its MTF is surprisingly good.

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Bart van der Wolf - 26 Aug 2005 21:22 GMT

SNIP

> Using a statistically insignificant sample size (2) I noted that
> the 10-22 EFS and 17-85 EFS do not have charts.

There are charts, but not all sites carry all of them.

This one also has EF-S charts, although you need a bit of imagination
to get them ... (or a web-translator):
http://cweb.canon.jp/camera/ef/catalog/category/
Note the smaller radius when comparing to non-EFs lenses.

Bart

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Bill Tuthill - 29 Aug 2005 18:07 GMT

> This one also has EF-S charts, although you need a bit of imagination
> to get them ... (or a web-translator):
> http://cweb.canon.jp/camera/ef/catalog/category/
> Note the smaller radius when comparing to non-EFs lenses.

Thanks again.

The Canon MTF charts show that the 17-85 EFS IS should be better
than the 18-55 EFS, although in real life situations the difference
doesn't appear to be great.

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