April 23, 2018, 10:20:32 AM

Author Topic: MTF Charts  (Read 601 times)

chrysoberyl

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MTF Charts
« on: April 12, 2018, 12:20:41 PM »
Should MTF charts supplied by different lens manufacturers be compared?  I don't see why not, but I defer to more experienced photographers.

Specifically, I want to buy a 50mm lens and when I compare the Samyang 1.2 to the Sigma Art, the Samyang looks very close.

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MTF Charts
« on: April 12, 2018, 12:20:41 PM »

Zeidora

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Re: MTF Charts
« Reply #1 on: April 12, 2018, 01:22:37 PM »
Should? not necessarily. Can? certainly, as long as you compare apples with apples. Depending on lens and manufacturer, they may or may not use the same spatial frequencies and may or may not show the data at same f-stop. I have not seen them given for all f-stops (even full f-stops). Usually all open, then f/5.6 or f/8, then either f/16 or f/22 or so. And then also for radial and tangential target orientation.

Would I base my purchase solely on MTF charts? Hell no! But it is a piece of information that at least has a normed acquisition pathway. So no room for ambiguities. Bokeh is one of those infamous subjective attributes.
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chrysoberyl

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Re: MTF Charts
« Reply #2 on: April 12, 2018, 02:22:44 PM »
Should? not necessarily. Can? certainly, as long as you compare apples with apples. Depending on lens and manufacturer, they may or may not use the same spatial frequencies and may or may not show the data at same f-stop. I have not seen them given for all f-stops (even full f-stops). Usually all open, then f/5.6 or f/8, then either f/16 or f/22 or so. And then also for radial and tangential target orientation.

Would I base my purchase solely on MTF charts? Hell no! But it is a piece of information that at least has a normed acquisition pathway. So no room for ambiguities. Bokeh is one of those infamous subjective attributes.

Oh, I would never base my purchase solely on MTF charts!  But I have the Samyang 14mm 2.4 and it is a pleasure to use.  So I conclude the 50mm will have similar construction.  I also expect it to have bokeh that is acceptable or better to me.  The weight and size do not bother me.  Coma is likely to be quite good.  I already have 86mm filters.

Flare, distortion, vignetting - I'm willing to take a chance.  So it comes down to resolution.

Thanks for the input, once again.

neuroanatomist

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Re: MTF Charts
« Reply #3 on: April 12, 2018, 02:30:37 PM »
Except for Zeiss, MTF charts are theoretical – computer generated based on the optical design.  My experience with Samyang lenses is buy three, test them and keep the best. 
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chrysoberyl

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Re: MTF Charts
« Reply #4 on: April 12, 2018, 02:40:52 PM »
Except for Zeiss, MTF charts are theoretical – computer generated based on the optical design.  My experience with Samyang lenses is buy three, test them and keep the best.

Based on the optical design - I am glad I asked!  Thanks.

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Re: MTF Charts
« Reply #4 on: April 12, 2018, 02:40:52 PM »