70-200mm F/2.8 IS II can't make background more blurred than 135mm f/2????

70-200mm F/2.8 IS II has longer focal length, however, its max aperture is 2.8. 135mm f/2 has shorter focal length, but it have wider max aperture.

So, Canon 70-200mm F/2.8 IS II at 200mm - f/2.8 and Canon EF 135mm f/2 at 135mm - f/2, what make more blurred background??? ( when take photograph of a same model at same size of that model's face/body (compare to full size of the picture))

It's not as simple as comparing focal length and aperture size. You would also need to take into account distance to subject and distance from subject to background, etc..

Clockwork Frog wrote in post #16500293
It's not as simple as comparing focal length and aperture size. You would also need to take into account distance to subject and distance from subject to background, etc..

when take photograph of a same model at same size of that model's face/body (compare to full size of the picture)

Walkundertherain wrote in post #16500296
when take photograph of a same model at same size of that model's face/body (compare to full size of the picture)

If I understand you correctly, and forgive me if I don't, I think you are saying that with the same framing, i.e. with the subject the same size in the shot? In that case, the 135mm lens would have to be closer to the subject than the lens at 200mm, in order to achieve the same framing .

Here are the VWDOF calculator results:


Adjusting object distance for equal framing (4 and 2.7m resp.), the zoom at 200/2.8 delivers a more intense blur at infinity, while the 135/2 gets you more blur on background located 5m behind the object (POI = Point Of Interest: could be set relative to camera or object).

You can download this calculator to better research the various cases - very informative! IIRC, the APS-C sensor size has to be added to the list by the user.

http://toothwalker.org​/optics/vwdof.html

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Clockwork Frog wrote in post #16500293
It's not as simple as comparing focal length and aperture size. You would also need to take into account distance to subject and distance from subject to background, etc..

I don't think this guy understands lol

In the grand scheme of things why does it even matter? Can you actually spot the differences between them? The DOF at 2.8 @200mm on the 70-200 is razor thin too, that much you do notice. Blurred out of focus areas isn't a reason I'd buy a lens or not.

OneJZsupra wrote in post #16500359
I don't think this guy understands lol

He is speaking perfect sense, so what is it you don't like about his comment?

Paulstw wrote in post #16500500
Blurred out of focus areas isn't a reason I'd buy a lens or not.

For portraits it very much is.

Edit:: I remember someone on this board saying: I spent so much money on the EF 85/1.2 ... to have 90% of the picture out of focus.

OneJZsupra wrote in post #16500359
I don't think this guy understands lol

focal length, aperture size, distance to subject, and distance form subject to background etc. What else is there looks like all the important parts of the equation are covered.

200mm WILL make better background than 135, and 85 1.2, but working distance is tough to work with.

Charlie wrote in post #16500933
200mm WILL make better background than 135, and 85 1.2, but working distance is tough to work with.

Not necessarily: depends on distance to background, as shown by the calculator above.

For me 70-200mm f2.8 IS II is more flexible.

Here at 120mm f2.8

The more appropriate comparison for this pair would be the 70-200 @ 135mm f2.8 and the 135 f2 with the same framing, I would think. In which case, no, the zoom will not produce the same or more blurred background.

As others have said, though, you can adjust position. of camera/subject/backgro​und to modify that result.

Here:

135mm @f2