can 70-200L F4 IS replace Sigma85?

as titled.
thanks in advance

Well, if you never use it faster than f4, then, yes.

It's very hard for someone else to answer that for you. Why are you considering it ?

If you want an f4 zoom instead of an f1.4 prime, then yes. In the same way as a 10mm fisheye could replace a 600mm telephoto if you want a 10mm fisheye instead of a 600mm telephoto.

for portrait shots. can 70-200 f4 IS replace sigma85?

Dr.TC wrote in post #12503988
for portrait shots. can 70-200 f4 IS replace sigma85?

bohdank already answered that for you. If you never use your 85 1.4 faster than f4, then yes.

If you only need f4, then yes. Honestly, these are 2 completely different lenses to really be able to answer this question.

Dr.TC wrote in post #12503988
for portrait shots. can 70-200 f4 IS replace sigma85?

In some ways, yes. You can take great portraits with either one, but they'll both have their benefits.

If we're talking strictly studio headshots here, I think I'd prefer the 70-200. Upper torso and full body portraits, the 85.

For me it wouldn't. YMMV.

I dont think so imo, my 85 1.8 Canon is one of my preffered lens
Then again also is my 70-200
the beauty of the fast 85 is the control on DOF that you get
Although the 70-200 is very sharp, it will give you well only f4, you can zoom to 100 to 200mm and shrink the DOF but then your compression and FOV is different and you'll need to be much farther away from your subject
Both lens complement each other nicely IMO

Dr.TC wrote in post #12503988
for portrait shots. can 70-200 f4 IS replace sigma85?

It depends on what kind of portraits you are trying to take.

I do a lot of portrait shots with my 85mm around f/2.8. You can get the eyes tack sharp with great bokeh background.

On the other hand, if there is more than one person in the picture, the DOF is too narrow to get everyone's face in focus at f/2.8, so I usually use f/4-5.6. For these kind of pictures the 70-200 f/4 would be fine.

In terms of its ability to blur the background into oblivion, 85/1.4 will do a better job (by 20%) than the 70-200 f4 at the longest FL (the background blur for remote objects is proportional to the size of entrance pupil of the lens, or FL divided by the aperture number; for Sigma, it's 85/1.4~60mm, for Canon, it's 200/4=50mm). Also, with the Canon at 200mm, you'd have to stand 2.4 times farther for the same foreground framing, and will get much less background into the photo (background compression) - but if all you need is to annihilate the background, it shouldn't matter.