Cropping of M240 files for different FOV

[jmahto]

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Did the cropping analysis on M240 file for different focal lengths FOV.

It is useful to me since I go out with just 15mm and 28mm for nature hikes. I wanted to know how much I can crop.

 

Note that I used focal lengths which I have, that's why 35mm is missing but it is close to 40mm.

 

Copping of 15mm to other FOV:

15mm to 21mm (15 on APS-C): 24 to 11 mp : Good for A4 print

15mm to 28mm: 24 to 7 mp : Good for A4 print

15mm to 40mm: 24 to 3.5 mp : Good for 5x7 print

15mm to 50mm: 24 to 2mp : Good for 4x6 print (still good for web viewing)

 

Copping of 28mm to other FOV:

28mm to 40mm: 24 to 12 mp : Good for A3 print

28mm to 50mm: 24 to 7 mp : Good for A4 print

28mm to 60mm (40 on APS-C): 24 to 5 mp : Good for 5x7 print

28mm to 90mm: 24 to 2mp : Good for 4x6 print. (still good for web viewing)

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[bocaburger]

I never went to that length to calculate, I just figured if I crop any lens to effectively double it's focal length, it will effectively halve the number of pixels, and 12mp is still very usable up to 16x20 because my 10 yr old CMOS Canon 5D is 12 mp and it does 16x20 beautifully.

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[jmahto]

I never went to that length to calculate, I just figured if I crop any lens to effectively double it's focal length, it will effectively halve the number of pixels, and 12mp is still very usable up to 16x20 because my 10 yr old CMOS Canon 5D is 12 mp and it does 16x20 beautifully.

 

Thanks, this is easier rule of thumb to remember. However my analysis showed that doubling the focal length reduces pixels to 1/3 (not half as you mentioned).

 

As for print size, I used 300dpi to calculate. I have noticed that doing less than 200dpi from my old Canon 40D (even with good glass) required very good pic to start with (that's why I seldom did 16x20. Mostly it was up to 11x16 from 10mp).

 

With my M9 and M, 200dpi is no brainer since the files are so sharp to start with.

[bocaburger]

You're correct about the change in pixels, it's not linear. That would be because the change in fov is not linear, as the change in fov decreases inversely to the increase in focal length (the difference in angle of coverage between a 25mm and 50mm is greater than between a 50mm and 100mm for example). I mainly crop 135mm shots because there are no native (mount to the body, couple to the rangefinder and focus to infinity) lenses longer than that. Now that the M240 has the EVF it's possible to use longer SLR lenses. Still that means increasing the weight and bulk of the kit.

[jaapv]

I don’t think that I agree with the “good for xx print”. I have had excellent A2 prints done out of 10 MP on the M8 and have seen pretty good A3 ones out of 6 MP or even less.

The simple mathematical approach of divide the pixels by 300 is not representative of good printing technique and certainly does not take the content of the image into account.

[jmahto]

I don’t think that I agree with the “good for xx print”. I have had excellent A2 prints done out of 10 MP on the M8 and have seen pretty good A3 ones out of 6 MP or even less.

The simple mathematical approach of divide the pixels by 300 is not representative of good printing technique and certainly does not take the content of the image into account.

 

I somewhat agree that 300dpi should not be general rule. Recently I tried to print a good samples of my old pictures and noticed that the pics from M were good enough till 180dpi (even for hand held distance viewing) but my old Canon photos were inferior at 200dpi. Partly it was related to my poor shooting technique. I relied on autofocus and many times shot in P mode letting camera choose the aperture (I have landscapes at f22 without any valid reason !!).

 

Printing technique is another area where I have little to no experience. Hope to keep learning.

Edited November 26, 2014 by jmahto

[A Almulla]

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TV sets from the 1950s would be better viewed from a distance than up close when compared to current TV sets and has a lot to do with the screen quality and resolution.

 

Printing an image in A3 and looking at it from 6 inches away compared to 10 feet away is not the same. The greater the distance you are looking at an image the lower the required resolution.

[jaapv]

I somewhat agree that 300dpi should not be general rule. Recently I tried to print a good samples of my old pictures and noticed that the pics from M were good enough till 180dpi (even for hand held distance viewing) but my old Canon photos were inferior at 200dpi. Partly it was related to my poor shooting technique. I relied on autofocus and many times shot in P mode letting camera choose the aperture (I have landscapes at f22 without any valid reason !!).

 

Printing technique is another area where I have little to no experience. Hope to keep learning.

 

There is a lot to it. For instance proper resizing will result in little to no visible quality loss.

[epand56]

Forgive the ignorance, but what (APS-C) stands for?

[jaapv]

Sensor size.

 

APS-C - Wikipedia, the free encyclopedia

[jmahto]

Leica T is APS-C sensor size camera whereas M is full frame that's why I showed APS-C frames as well.