Canon 70-200 f/2.8 IS III vs Similar f/4.0 for Canon 90d (or any crop sensor)

by Miles Hanley
(Columbia, SC)

"I just purchased the Canon 90d and bought the ef-s 17-55mm f/2.8. I am looking at purchasing the Canon 70-200 f/2.8 is iii and I just read your article on the 70-200mm f/2.8 vs. the f/4.0. You made some compelling arguments for getting the less expensive f/4.0. And this would make sense on a full frame camera. But with crop sensor cameras the crop not affects the focal length but also the minimum and maximum (if not constant) aperture. So the f/2.8 is effectively an f/4/5 and the f/4.0 is effectively f/6.4. Would this make it more sense to purchase the faster lens with a crop sensor camera?"

Hi Miles,

Congrats on choosing the 90D. I am really enjoying mine too, for several reasons! The topic of the comparison of the Canon 70-200 f/4 vs. f/2.8 is a fascinating topic for Canon nerds like me (and perhaps you). My biggest points for choosing the f/4.0 vs. the f/2.8 are price and size. But, I've got to tell you. You can't go wrong with choosing the 70-200mm III.

Effective f-stop on Full Frame vs. 90D crop sensor

Although technically maybe the "effective" f-stop might be different, it's the practical differences that matter. Whether you use am f/4 lens or an f/2.8 lens set on f/4 the same amount of light will enter your 90D all the same. If you can afford the f/2.8, you're going to love it. I've been shooting the majority of portraits I shoot with the 70-200mm f/2.8 I for many years.

Also, How many times will you be shooting either of the 70-200mm lenses at the smallest apertures? The amount of benefit of having that extra full f/stop (twice as much) and the added background blur (bokeh) are the 2 factors that make the most difference in your shooting.

I encourage you not to get too wrapped up in minor technical differences-I'm guilty of this frequently-and focus on your technique and creativity.

Miles, Thanks for your question about choosing a Canon 70-200mm f/4.0 versus the f/2.8 version. I think it's just a matter of the situations you're in, both financially as well as the situations you photograph.

I look forward to hearing back from you to see whether you select the 70-200 f/2.8 III or the f/4.0.

Thanks,
Bruce
Canon 70-200 f/2.8
Canon 70-200 f/4.0