Buying advice: Canon 16-35mm f2.8 vs 16-35mm f4 for 5D classic

[Robin]

Is the difference in capability between f2.8 and f4 substantial?

16-35 F2.8 is often sold for less price in the used market, than the 16-35 F4. Why?

I have 50mm F1.8 STM prime and now on a hunt for used 70-200mm f2.8 for my 5D Mark I. I'm thinking 16-35mm should fill the 'wide angle' gap. Or should I get a 35mm prime (or) 24-70mm f2.8?

Based on my experience with 50mm F1.8, I realized that I'm more of a portrait guy, and enjoy looking at portraits I shot 80% of the time or may be I have limited experience in wide angle, as I'm yet to try.

Not interested in buying brand new lenses, so will look at used market. Recommendations for someone in tight budget, please ?!

[Bharat Varma]

There are three versions of the 16-35 F/2.8.
There's only one version of 16-35 F/4.

16-35 F/2.8 version 3 or by far the very best, but very expensive. The F/4 is also a very good lens indeed, and very highly recommended.

If you are on a tight budget and more into portraits, just close your eyes and get the Canon 17-40 L F/4 lens. Greatest range, very sharp in the center, lovely L lens colors. Relatively very cheap as well.

[Robin]

Thanks!! Checked few more reviews and made up the mind.
Not seeing any 17-40mm f4 L in the classifieds. Will post a WTB and wait.
Hoping I find a reasonably priced one here itself.

[Robin]

Got the Canon 17 - 40 f4 L outside the forum.
Thanks for the recommendation, Bharat! This topic can be locked.