Reading MTF charts

[Hiding_Pup]

I've just been wondering - and maths was never really my strong point - how much of the x-axis of any MTF chart do M8 users need to take account of? Presumably there's a chunk on the far right that measures things that have long since fallen off the edge of the sensor?

 

[35mmdelux]

Huh? The MTF charts simply desribe the charateristics of the lens, not the camera, no? In other words, the lens is what it is.

 

[sojournerphoto]

Huh? The MTF charts simply desribe the charateristics of the lens, not the camera, no? In other words, the lens is what it is.

True, but it's not all relevant to the M8 as the smaller than 35mm frame sensor doesn't 'see' that part of the image circle.

Mike

 

[Tom Niblick]

As I understand things, you can disregard the far right of the chart when looking at using a lens on a M8.

Here is a brief guide to MTF curves:

http://www.photodo.com/topic_108.html

And here, for example is an independent MTF curve for a 35 Summicron type IV

http://www.photodo.com/product_917_p4.html

 

[Rob-F]

Sure, it makes sense that one may disregard the extreme right of the X-axis. The M8 sensor has a 1.33 crop factor, so the M8 diagonal is 43mm / 1.33, or 32.3mm. (Because the full 35mm frame diagonal is 43mm.) Thus you may disregard the area to the right of 32.3mm. (Call it 32mm for all practical purposes.)

 

[amigadave]

Sure, it makes sense that one may disregard the extreme right of the X-axis. The M8 sensor has a 1.33 crop factor, so the M8 diagonal is 43mm / 1.33, or 32.3mm. (Because the full 35mm frame diagonal is 43mm.) Thus you may disregard the area to the right of 32.3mm. (Call it 32mm for all practical purposes.)

The x axis of MTF charts is defined as a radius from the centre of the lens' imaging circle, not as a distance across a diagonal (although the maximum radius will be to the corner of a frame, i.e. along the diagonal), so 32.3 mm / 2 ~= 16 mm. The MTF curve after 16 mm can be ignored for use on an M8.

 

[Hiding_Pup]

Cheers, guys!