Busting the Lens dictates Focus Speed Myth

Started Mar 22, 2013 | Discussions
meland
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Re: More experience required
In reply to Schwany, Mar 25, 2013

Schwany wrote:

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?

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)?

Whats your take on it?

You need to try a larger sampling of lenses, and get in some experience photographing fast moving subjects. I agree that bodies do make a difference in focus speed, but there are certainly faster focusing lenses than others. Canon even makes a point of it in their product literature for the big Whites.

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.

My personal experience differs from yours. I've used and own many lenses. They are not all the same in sharpness nor focus speed. All of them would work equally well for cats though.

How about ducks?

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Suave
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Re: More experience required
In reply to Schwany, Mar 25, 2013

Cats?  Real photographers shoot brick walls.

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Scott Larson
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Re: Busting the Lens dictates Focus Speed Myth
In reply to MAC, Mar 25, 2013

MAC wrote:

Sovern wrote:

The 85L supposedly AF's noticeably slower than my 85 1.8 according to the lens "gurus". But I don't believe it.

The L is slower. But it can track people fine in AIServo.

Lens speed comes into play in action photography and AI Servo. That is where the 70-200 F2.8's for sports shine.

The cameras can compensate for the slower focus but the frame rate slows down. For kicks I tried shooting basketball with the 85mm f1.2. Yeah, it tracked but the frame rate on my 1D Mark IV went from "clickclickclickclick" to "click........click.......click.......".

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Sovern
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Re: Busting the Lens dictates Focus Speed Myth
In reply to Sovern, Mar 25, 2013

So the conclusion that I've drawn is that for fast moving subjects the differences in AF are apparent due to using AI Servo and the lens having to lock onto focus fast.

When photographing slow moving subjects such as people lens AF speed is not as important and won't make much of a difference because the lens can lock onto focus easily due to the subject not moving around very fast making the lens not have to change it's focal point.

Makes sense to me.

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Schwany
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Fortunately for me
In reply to Suave, Mar 26, 2013

Suave wrote:

Cats? Real photographers shoot brick walls.

Fortunately, I'm just a figment of my own imagination, and have no aspirations of becoming real anytime soon.

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Schwany
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About ducks
In reply to meland, Mar 26, 2013

meland wrote:

How about ducks?

I made that stuff up about cats. Don't have one. I just assumed any lens would work for a cat, and always be sharp and focus well enough to wow a cat person.

Some lenses are better for ducks than others though.

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joger
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Re: Busting the Lens dictates Focus Speed Myth
In reply to Sovern, Mar 26, 2013

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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irm
irm
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Re: About ducks
In reply to Schwany, Mar 26, 2013

Sorry, not this little black duck. While most of my cat shots are static there are time when a fast focusing lens is a boon. The best lens so far that I own for cat shots static of action is the 135 f2 L, but the one I sold and have since regretted was the 70-210 f4. I t was a light weight, very fast focusing lens on a 10D. Small close focus so allowed use in a confined space.

Pity the lens was discontinued.

Ian

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bertliza
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AF of the lens matters.
In reply to Schwany, Mar 30, 2013

I have a 40D, a Canon 17-55 f2.8 and a Tamron 17-50 f2.8. With the same camera setup and certain low light condition, the Canon 17-55 f2.8 mm can lock its AF but a Tamron 17-50 f2.8 would continuously hunt, and refuse to AF.

AF of the lens matters.

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kevindar
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Re: Busting the Lens dictates Focus Speed Myth
In reply to Sovern, Mar 30, 2013

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.

you are definitely blessed to find no sharpness difference between lenses or autofocus speed difference, and anyone who tries to convince you otherwise is doing you a great disservice.

and you know what, in many appllications, if there was a focus speed difference between the 85 1.8 and 50 1.8, or tamron 17-50 or kit lens (and I already told you I would never try to convince you there is a difference) you are correct that its inconsequential.

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WilbaW
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Re: Busting the Lens dictates Focus Speed Myth
In reply to meland, Mar 31, 2013

meland wrote:

The maximum aperture of the lens - a wider maximum aperture will let more light through for the AF system to do it's measurement.

(Assuming you're not just talking about the f/2.8 threshold that switches between the standard and high precision AF sensors...) No, the AF sensors don't see the scene like the image sensor does. Think of the image sensor as seeing the brightness in the room, and the AF sensors as telescopes looking through a window. If you open the curtains the room gets brighter but images through the telescopes don't get brighter.

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Sovern
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Re: Busting the Lens dictates Focus Speed Myth
In reply to Sovern, Mar 31, 2013

As an update to this thread, I'm going to do a video of the AF differences in shooting still life in low lighting conditions starting out with comparing the Canon 85 1.8 to the kit 18-55 lens......I'll update this thread when I get around to making the video and writing my findings.

So far let's just say that even in poor lighting conditions the 18-55 locks onto focus nearly as fast as the 85 1.8......this will help beginners and other enthusiasts know that they don't need to spend hundreds or thousands on more expensive lenses because they heard that a particular lens AF's much faster than a cheaper one.....

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WilbaW
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Re: Busting the Lens dictates Focus Speed Myth
In reply to bhollis, Mar 31, 2013

bhollis wrote:

the change in focusing speed when I put a 1.4x TC on my 70-200 f/4L IS is very noticeable.

That would be because the TC alters the relationships between the parameters required to calculate the lens commands. It's very apparent with a short extension tube - focus converges on the target by oscillating between front and back focus, rather than approaching the target from one direction.

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