EF 20mm f2.8 vs EF 24mm f2.8 IS vs EF 28 f1.8

Alan GT wrote:

Hi - why don't you just buy the ultra cheap EF-S 24 2.8 pancake lens for your 400D? You won't get any real image quality advantage on the 400D with the much more expensive EF 24 2.8 IS other than it having IS. The pancake is cheap enough not to worry about the fact that it is APS-C only, and you can easily sell it. If you upgrade to FF you could always get the similar EF 40mm pancake or as someone else sugggested the EF 35mm f2 IS.

Alan

Ditto. HIts the bullseye on all your requirements:

1. Use on an EOS 400D body for inconspicuous street photography - this is the primary intention.

Nothing is smaller, lighter, less conspicuous

2. Use of the lens on a full frame body (most probably 6D, yet to be purchased) for indoor low light photography, size is less of an issue here. This also means that EF-S or third party crop-only lens are out of the question.

I reject this out of hand. Buy lenses optimal for the camera system you have. You'll spend more for a suboptimal solution if you buy lenses for a camera you don't have.

Requirements:

1. Fast lens (at least f2.8)

Check.

2. Small as possible (preferably similar in size to the 50 mm f1.8 which I own)

Check, none smaller.

3. Wide angle field of view up to effective 40mm (meaning 28mm lens on the 400D), preferably in the vicinity of effective 28-35mm.

Check.

4. Budget up to 700 USD.

$150 USD retail, $120 from Canon USA Refurbished with free shipping (but add state sales tax) and same 1yr Canon USA warranty as new).

https://shop.usa.canon.com/shop/en/catalog/ef-s-24mm-f-28-stm-refurbished