Beginner Another Canon "portrait" lens type question.

[Zimmer]

I have made the plunge and have a Canon 6D en route. (ssshh don't tell wife )
I already have a 100mm Canon 2.8 Macro (non L), and a 24-105L. and someday, I will get a 70 - 200 f4 IS

Was reading the 50mm vs 85mm portrait thread here, I started thinking to myself (dangerous, I know)
I know it's a kinda nonsensical pondering, but

Say if shooting an outdoor portrait in decent light and using f4 with each of the following:

Canon 85mm f1.8 (and walking forward a little lol) - f4
100mm f2.8 Macro - f4
24-105L f4 at 100mm - f4
70 - 200 IS f4 at 100 - f4

I was wondering, assuming all lenses are sharp copies, would there be much/any image quality difference in the 4 shots ?
Could an "expert" tell without exif which lens was used.
Assuming the composition was fine and f4 was the chosen aperture, would a "pro" just use whichever lens happened to be ON the camera ?

 

[woof woof]

Lenses are often better stopped down a bit so maybe a f1.8 or f2.8 lens will be better at f4 than an f4 lens?

If you can Google your way to some lens reviews they may well tell you at what aperture each of your lenses performs best at or you could just shoot a series of shots at wide open to decreasing aperture and decide what looks best as what aperture lenses are "best" at is maybe a different question to the final image and what you think looks "best."

 

[Zimmer]

Thanks m8, I understand that and have read zillions of lens reviews. It was more a generic question, than which lens is "best"
Was just wondering in the "real world" at normal sizes, at similar apertures and focal length, would anyone even notice the difference between any of the "good" lenses listed above.
I suspect not, but then maybe I should just go to bed, rather than posting nonsense after a few beers.

 

[MatBin]

I have the 85 1.8 and it needs stopping down to 3.5 before its as sharp as my 70/200 f4 L wide open. I also have the 100 2.8 macro. Assuming you have enough room between you and subject I think the macro would give the best results, partly because its not as imposing as the zoom (white) lens and it is sharp wide open, although better at f4. No experience of the 24/105. I also have a 24/70 ,2.8 and that would be the lens I would use if I could frame OK.
All the lenses are good though, maybe too god depending on sitters age and sex
Matt

 

[woof woof]

Thanks m8, I understand that and have read zillions of lens reviews. It was more a generic question, than which lens is "best"
Was just wondering in the "real world" at normal sizes, at similar apertures and focal length, would anyone even notice the difference between any of the "good" lenses listed above.
I suspect not, but then maybe I should just go to bed, rather than posting nonsense after a few beers.

Isn't this what a forum is for?

Personally, the look, bokeh etc... would be more important to me than ultimate sharpness.

For example I recently compared some old manual 50mm lenses to my spanking brand new Sony FE 55mm f1.8 and there's no denying that the new 55mm is better in any measureable way but that doesn't stop pictures taken with the old lenses looking nice and in fact some of my most favourite portraits have been taken recently with old manual lenses but probably not wide open, maybe stopped down.

 

[andy1868]

Not all lenses are created equal due to different element configurations, coatings, aperture setups...... Another thing to bear in mind is distortion, be it barrel or pincushion or anything in between (I have a cheap Cosina that has moustache distortion )

There's plenty to make them look different with different characteristics but I find this is half the fun of researching new lenses and the perfect excuse for GAS "yes I know I already own 4 50mm lenses but THIS one is different"