Busting the Lens dictates Focus Speed Myth

Started Mar 22, 2013 | Discussions thread
joger Veteran Member • Posts: 5,021
Re: Busting the Lens dictates Focus Speed Myth

Sovern wrote:

Why is that I hear so much on this forum and other forums that more expensive lenses especially primes AF faster than cheaper lenses and the kit lens a long with other cheap but more than capable lenses are such a bad lens for AF speed?

I have one of Canon's fastest focusing lenses (Canon 85 1.8 USM) and the kit lens and they both AF at the speed speed no manner the lighting conditions.

I have also had the Tamon 17-50 2.8 and 50 1.8 in the past and have never felt a difference in AF speed between any of these lenses they all lock on focus very fast.

Is this "This lens has faster AF" a myth sort of like how people claim that their $2,000 prime is "sharper" than a $350 primes or zoom (myth in my opinion)?

From what I have read the AF focusing system built on the camera determines the AF speed and not the lens itself (besides cycling between MFD and infinity being a minor difference obviously).

Whats your take on it?

Personally I'm not convinced.

I believe from my own personal experience that the body determines AF speed as my 40D AF's faster than my xsi but all of my lenses AF just as fast/precisely no manner the lighting conditions from my own experience using them myself.

rent the lenses you're interested in and try them. There's fortunately a lot of places where you can have a two or three day run with the lens of your 'desire' and get your own impressions.

Don't trust the hype of things and don't trust forums where the gear owners try to connivence you that their new toy is the best you can get - there seems to be a clear agenda at some of the posters.

Get your own hands on and judge yourself. It might be useful for some to use this or that combination instead of another - the only guy that can judge is yourself.

The funny thing is that people judge on combinations they actually never tested for more then a few images or never had in their hands.

It is also deponent on the light conditions and most of all on your personal ability to get the utmost out of your gear. There is a certain level of craftsmanship that is required to work on the differences.

Not everyone would drive a formula one car the fastest possible way around the race track - keep in mind that the mileage of different photographers vary and it is not necessarily a black and white judgement possible all the time.

What works good for you must not be good for someone else necessarily.

BUT excellent (speed optimized) primes like the new type II tele lenses from Canon just are a bit faster then the rest of the lenses in this area - no doubt that a 85 f/1.2 is not speed optimized - this lens has a different purpose. Try to understand that every lens is built to a certain user profile.

There are aspects like convenience, weight, optical resolution, bokeh and AF speed that can be better or worse - not necessarily expensive lenses are faster - speed optimized lenses are faster in combination with an appropriate body - try and find your what suits you rather then believing what some "specialists" suggest.

That said it is always good to get a first impression with forums and tests - it is a good starting point and that's also the reason for me to contribute to forums to give others an out of the box thinking start.

just my 2CT

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