I know this has been asked alot..

I have Canon 600D with Canon EF-S 18-135mm f/3.5-5.6 and Canon 50mm f/1.8 lenses.

I'm looking to upgrade the zoom lens with something with better IQ, sharpness, bokeh and low light performance.

I read alot about those 2 Sigma lenses and I understand that the compromise is between constant aperture and additional reach.

I mostly shoot at outdoor trips / hikes, etc.. and have my first baby on the way so it'll be used for family shots as well.

I'm also using my camera for mountain biking videos, using those 2 lenses I have and some vintage manual lenses.

I need some expert advice for choosing between the 2 Sigma lenses..

  • \$\begingroup\$ i recently bought the 17-70(c), was in the same descission. read a lot of reviews, compared many sample-images and so on :) the main reason why i bought the 17-70 was the macro-ability and the higher zoom. but it depens on your needs. sharpnes is great but not as good as your prime 50mm \$\endgroup\$
    – fubo
    Commented Aug 18, 2014 at 8:03
  • \$\begingroup\$ DON'T GO FOR THE Sigma 17-50/2.8 !!! I have/had one by my own: It has strong back focus problems at photos with light background and small motive. And also: one of the inner lens elements become lose! My Sigma 17-50/2.8 is trash now. \$\endgroup\$
    – Horitsu
    Commented Jun 26, 2018 at 4:46

2 Answers 2


I'd go with the constant f/2.8 version. I don't think I've ever used my Canon 17-55/2.8 wide open at less than 55mm, yet have used it wide open @ 55mm a lot, especially for pictures of people (including babies).

The IS allows me to use a lower shutter speed at f/2.8 than my 50 f/1.8 wide open, albeit with wider depth of field.


This really comes down to a personal choice: whether you prefer the constant aperture and slightly better center of frame sharpness of the 17-50 or the extra reach and better sharpness on the edges and in the corners of the 17-70. For the outdoor stuff the reach of the 17-70 is probably a little better, but for the family photos (especially indoors) the f/2.8 is what you would want.

Why not get the best of both worlds with the Tamron 24-70mm f/2.8 Di VC? It outperforms the original Canon EF 24-70mm f/2.8 L, includes Vibration Compensation (Tamron's version of IS), and is quite the lens for the price. It normally sells for around 1,100-1,200 USD but I've seen it on sale for 750-850 USD several times.

Several years ago I went with the Tamron 17-50mm f/2.8 and have never regretted it. For the money it was a great lens that I got many good shots with until I moved on to shooting most wider angle stuff with a full frame camera. On the rare occasion when I need to shoot wide angle on an APS-C body I still reach for the Tamron 17-50 over my EF 17-40mm f/4 L. On the APS-C bodies the Tamron is a full stop faster and ever so slightly sharper than the "L".

  • \$\begingroup\$ I know the no one lens can do it all.. If I keep the entry level 18-135 would you say I better get the 17-50? \$\endgroup\$ Commented Aug 16, 2014 at 9:22
  • \$\begingroup\$ Tamron 24-70mm is a full frame lense - if you calculate with a crop factor 1.5 you get a 36-105 \$\endgroup\$
    – fubo
    Commented Aug 18, 2014 at 7:58
  • \$\begingroup\$ @fubo Since the "crop factor" for Canon is 1.6x, the 24-70 shows a 38-112mm Full Frame FoV when attached to an APS-C camera. In which case for comparative purposes the 17-50 is a 28-80mm. Focal length is focal length and has nothing to do with sensor size. If you are comparing a FF lens and an EF-S lens you need to multiply both by the crop factor to get the equivalent FoV. \$\endgroup\$
    – Michael C
    Commented Aug 18, 2014 at 12:26

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