15-85 or 17-70

Started 3 months ago | Discussions thread
Wave forest Regular Member • Posts: 350
Sigma 17-70 C rather than Canon 15-85 IS

If we have to choose between these two: Sigma 17-70 C or Canon 15-85 IS, it would be Sigma 17-70 C.

The reason are:

1. It is about one stop faster, making is more usable in low light situation, such as indoor or evening.

2. It is half price of Canon 15-85 IS.

3. It is very sharp, *if* tuned properly.

There are many reviews online on the two. However, the main difficulty of a Sigma lens is that it has to be tuned and the tuning may take a long time.

I have some discussions in User Experience of Sigma 17-70mm f/2.8-4 DC Macro OS HSM C with photos before tuning and after tuning and photos of StillLearning

For many comments which are not happy with the IQ of Sigma 17-70 C, a general issue I read is that they didn't claim they had tuned the lens into its optimal condition. In addition, I don't have the impression that they tried this lens with live view or manual as I did. Apparently, they only tried AF and made the claims. A Sigma lens has to be calibrated and tuned.

If the IQ of live view or manual is okay, the lens will be fine. because for Sigma or other third party lens manufacturers, there is no problem for them to mimic a Canon or Nikon lens, if both camera body and lens are in absolute precision. However, discrepancy on either lens or body, or both, happens and, as a result, variation is inevitable. For a native lens, as long as no obvious defect, i.e. in focus, a customer is happy, but this lens may not at its optimal position at all. This is why a high end camera has AF micro-adjustment.

For a Sigma lens, by calibration, not only can we know it is in focus, but also can we know it is in its optimal position.

To smummarise, Sigma 17-70 C is a better choice - it's reasonably priced, it's more versatile in tough condition and importantly, we can be confident with its AF.

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