Next week I hope to get a good chance to do my first Milky Way shoot. Last thing I struggle with is which of my lenses to use. I want to avoid startrails. In the final round are:

  • Sigma 17-50 2.8
  • Canon 10-18 4.5-5.6

From my point of view it is clear if I choose (17/) 18mm the Sigma wins because of 2.8 against 5.6, but what is to prefer if I use widest angel on both lenses?

What to prefer Sigma@17mm 2.8 OR Canon@10mm 4.5

I tend to use the Sigma, because 10mm - now my thesis - will give me more stars/Milky Way, but 4.5 is a bit slow. Is it only a question of perspective or will give me 10mm 4.5 more light than 17mm 2.8?

  • 1
    Do you have a fullframe body? What body do you have? This is going to differ based on if you are using a 6D or a Rebel T1i
    – tjons
    Aug 18, 2014 at 20:34
  • @tjons: No fullframae. I'm using a EOS 70D.
    – Micha
    Aug 19, 2014 at 10:12
  • Note that there is a Samyang/Rokinon 10mm f/2.8 lens available for APS-C cameras that costs about the same or less. Aug 26, 2014 at 21:51

1 Answer 1


If your goal is to minimize star trails then the wider aperture is always preferred.

The wider angle lens will allow you to get more of the milky way in a single shot, but if you are comfortable and willing to stitch multiple images together then it doesn't matter much.

See: How do I capture the milky way?

  • Thanks for your answer! I know the link and the "600 / focal length * crop factor"-rule to avoid startrails. that was one reason which confusing me, because with 17mm I can take a shot with 22 seconds exposure and with 10mm I get 37 seconds exposure time. But if I interpret your answer correctly 22 sec is still "better" than 37 sec because of the much better aperture 2.8 v.s. 4.5? But on the other hand it is logical becaue from 2.8 to 4.5 it is 1.33 f-stops faster, which is much much more light (about ~2.5 more?). Am I correct with that?
    – Micha
    Aug 19, 2014 at 10:25

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