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[quote name='nandadevieast' timestamp='1355759557' post='21212']

Hi,

I have a question to you, great if you can help me:

This 70-200 F4 has a MFD of 3.2 ft...but it has F4 only

The nikkor 180 F2.8 has a MFD of 5 ft...but it has F2.8

Which one will have smoother/less DOF at the long end (200mm), at MFD of course, lets say, while shooting a portrait (head/head and shoulder).

What if we are shooting not at MFD but a full length plus some background kind of portrait?

All wide open.

regards,

anurag

[/quote]

It does not make sense what you ask. <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/unsure.gif' class='bbc_emoticon' alt=':unsure:' /> Both lenses have a different MFD, so both lenses will have a totally different framing. Why would you want to compare a shot of a nose and mouth with a shot of a head?



One can not say anything about the smoothness of the blur by looking at such specs.



With the same framing and the same FOV, obviously the f2.8 lens will have more blur and a more shallow DOF than the f4 lens.