2 wk. ago • 66%

Best Budget Telephoto Lens for Low-light photography

I’m trying to pick a DSLR-compatible Canon telephoto lens for wildlife photography in low-light conditions (also, I like doing urban candid photography/street photography from distances, so that too). Naturally, this means high ISO and low f-stop. For some reason, all I can find are like f-4; is that normal? Also, what’s with all the “telephoto” lenses that max out at 200mm? Shouldn’t something like 400mm be better? I suppose I don’t want something too bulky, so 400mm is probably pushing it but idk… if you have experience in this, let me know what you think. I can only seem to find a handful of options, and most are for mirrorless cameras which sucks because I don’t want too many camera bodies so getting ANOTHER one for this purpose would really clutter my shelves as I don’t have any mirrorless Canon’s.

Anyways, budget is tight, nothing north of $1000, let me know what you think!

Edit: Posted in wildlife photo community, but it was dead (no posts since like 2 months ago) so figured I'd move it here.

8 comments

Unfortunately, you're asking for the worst-case scenario for lenses. This has to do with physics, and how much glass is required to shape the light onto the camera sensor. These lenses exist.. but the prices are ooof

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Well there is a 800mm f5.6, and a 600mm f4, and a 400mm f2.8, but of course they are bulky and pricey. More light needs bigger glass.

And then there's budget lenses. You can't have it all at once.

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Cause physics. F-number is calculated by (focus length / diameter of entrance pupil). Say you want a 400mm focal length with max f2.8, your front element diameter would need to be 400/2.8 = 143mm. Looking at the Canon EF 200mm F2.8, which has a filter diameter of 72mm, 200/2.8 = 72. Math checks out.
(Edit: Front element diameter is not actually equal to entrance pupil diameter, but here let's just say it is. You can look up the physics if you're interested.)

Have you actually looked up the lenses yourself? Canon EF 400mm f2.8 lens exist, but you're looking at 10x your budget brand new, and really huge sizes. And if you want zoom on top of that? Just search the Sigma 200-500mm f/2.8, aka the "Bigma". I'd say you're better off using f4 lenses or whatever is within your budget, and try to work within the limits.

TLDR: If you want telephoto with super wide aperture, the lens would need to be massive, and expensive.

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- thank you for explaining!!!!
  
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  Happy to help!
  
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The words “low light”, “400mm”, “wildlife” (implying excellent autofocus), “DSLR” (old), and especially “budget” don’t belong together.

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- thank you haha. duly noted.
  
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If you want to sacrifice f-stops and gain budget, focal length and reduce bulkiness look into mirror lenses.

Otherwise the physics are just not in your favour. If you really want to use that lens look into selling your existing lenses or renting one.

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