New 400mm f2.8 L IS MkII or current 500mm f4 L IS?

[Scotty McAdam]

So Roger what your saying is
That they are all very similar in resolution.
For eg.
The 600 F4 would be the same cropped as the 800 f5.6 would be no crop?
Same goes with the 500 F4 etc?
Or is this comparing the 600 + 1.4x TC? etc.
Just to clarify i am a dimwit lol!.

[Roger Clark]

Roger, I am really trying to understand this stuff.

Basic question: is resolution the same as sharpness?

Possibly the same question in a different form. When you say, "The 800 f/5.6 plots between the 500 f/4 and 600 f/4" are you saying that the old 600 f/4 produces sharper images than the 800 f/5.6?

Hi Artie,
I see you posted this a year ago and I never answered (sorry--I must have been traveling).

Resolution is not the same as sharpness, though they tend to be related. For example, consider two closely spaced hairs on an animal in an image. Resolution is the ability to show that there are two hairs. Sharpness is how good those to hairs look. and perceptually is more about edge contrast.

Regarding 600 f/4 versus 800 f/5.6, put a 1.4x TC on the 600, and you will resolve slightly more detail (840 mm versus 800) and because the lens has a larger diameter, one gets the same signal-to-noise ratio per pixel. If the optics were perfect, the sharpness would be the same between the two lenses. Supertelephotos are close to perfect (diffraction limited), but not quite. So only those with experience can say which combination is sharper in real world situations. But I bet the new 600 II will push new quality and I bet the 600 f/4 II + 1.4x TC III will beat the 800 f/5.6 if the current 600 one does not. Have you imaged the same subject side by side from the same location with 600+1.4 and 800, with the same body (1D4 or 7D) and at the same ISO, exposure time and f/ratio?

Canon's MTF charts on the 600 f/4 II + 1.4x III show the combination to be very impressive and higher or equal MTF as for the 800 at most frequencies (image detail) and most positions in the image plane.

So Roger what your saying is
That they are all very similar in resolution.
For eg.
The 600 F4 would be the same cropped as the 800 f5.6 would be no crop?
Same goes with the 500 F4 etc?
Or is this comparing the 600 + 1.4x TC? etc.
Just to clarify i am a dimwit lol!.

Hi Scott,
Crop factor has nothing to do with resolution on the subject. Resolution requires 3 things:
1) focal length, 2) lens aperture (diameter) where larger lens has less diffraction, and 3) pixel size to sample the image, with smaller pixels sampling finer details.

600 f/4 + 1.4x TC = 840 mm focal length, lens diameter = 150 mm.

800 f/5.6 = 800 mm focal length, lens diameter = 143 mm

500 mm f/4 has only 125 mm lens diameter, so diffraction is greater than the 800 or 600.

Ultimate resolution is limited by diffraction and diffraction in terms of angular resolving power is set by lens diameter.

Performance metrics then favor the 600 f/4 assuming quality optics (which are impressive in version 1, and even better in version 2).

See also this related thread:
http://www.birdphotographers.net/for...V-better-noise

Roger

[Aravind Krishnaswamy]

Someone correct me if I'm wrong but it sounds like Moose is out to lunch. When attaching a TC, the depth of field would also be equivalent to f/5.6 (and not anything wider). I don't see a reasonable explanation of why it would be any different in that excerpt from his book other than him just claiming it to be so. It doesn't seem to make sense.

Bill

Well, yes and no. A 400DO f4 with a 1.4 has an effective f stop of 5.6 for light purposes, but the depth of field will only be around f4.6. So its not exactly equivalent to a lens made to 560mm f5.6.


Moose likes teleconverters for this depth of field effect.... If you'd like a good explanation, Moose Peterson has it in his book. You can find it on page 35 of http://books.google.com/books?id=6rM0UcvqfnwC&pg=PA37&lpg=PA37&dq=teleconverter+depth+of+field+moose&source=bl&ots=jAhC1HrPwb&sig=-jRgAeZox8w5EgP5_0beqqLbMfc&hl=en&ei=KTMpTfmGNoGqsAO6xYnHBw&sa=X&oi=book_result&ct=result&resnum=2&ved=0CCAQ6AEwAQ#v=onepage&q=teleconverter depth of field moose&f=false

And I agree with Lynn's assessment of the 1200.

Best regards
Don

[Roger Clark]

Someone correct me if I'm wrong but it sounds like Moose is out to lunch. When attaching a TC, the depth of field would also be equivalent to f/5.6 (and not anything wider). I don't see a reasonable explanation of why it would be any different in that excerpt from his book other than him just claiming it to be so. It doesn't seem to make sense.

Aravind,
You are correct. Attaching a TC changes focal length. Depth of field is set by clear aperture and focal length, so changing either changes depth of field.

Roger