Question about glass focus speed vs camera focus speed

nokout3839

Hi All,

Im starting to shoot some basketball and need faster glass for both focusing and shutter speed. I have a 350D and am looking seriously at the 85mm 1.8 USM. The question that has arisin from a previous thread on improving my shots:

Can my 350D keep up with the focusing speed improvements of the 85mm?
(I currently use the 18-55 Kit and a 75-300 4-5.6 if that helps for a basis of comparison)

Thanks, Nigel

cmason

nokout3839 wrote:

Hi All,

Im starting to shoot some basketball and need faster glass for both focusing and shutter speed. I have a 350D and am looking seriously at the 85mm 1.8 USM. The question that has arisin from a previous thread on improving my shots:

Can my 350D keep up with the focusing speed improvements of the 85mm?
(I currently use the 18-55 Kit and a 75-300 4-5.6 if that helps for a basis of comparison)

Thanks, Nigel

I don't think the lens helps that much in focusing speed. Of course, more light helps, but I have heard that focus speed really jumps when one goes to a pro model camera (1D..) or in some instances an L lens.

Of course 1.8 will certainly help with shutter speed, allowing you to open up, maintaining higher shutter speed settings in darker conditions. An IS lens can help as well, by giving you more stops at those higher shutter speeds (IS does not stop motion of course)

nokout3839

Still not sure

cmason wrote:

I don't think the lens helps that much in focusing speed. Of course, more light helps, but I have heard that focus speed really jumps when one goes to a pro model camera (1D..) or in some instances an L lens.

Of course 1.8 will certainly help with shutter speed, allowing you to open up, maintaining higher shutter speed settings in darker conditions. An IS lens can help as well, by giving you more stops at those higher shutter speeds (IS does not stop motion of course)

Thanks for the reply,

I still dont quite get this. If I went to a f1.8 lens then the autofocus should be able to work much faster (or is it better?) but by the sounds of it there is only so much the extra light can do after that a better camera is required. Does anyone have a 350D that has made a change like this that can offer a comparison? Does the auto focus points come into it? (I am using only one focus point).

Sorry to keep on about this but Im looking to spend the money soon.

Cheers

allan

This should help:

From: cwestfall@cusa.canon.com
Date: March 8, 2006 9:24:44 AM EST
To: allan michael <armichael@optonline.net>
Subject: Re: about this.....


Allan:

Most of our current cameras, including the 20D as well as the 30D and the 5D, offer the same level of high-precision AF on their center focusing point as the EOS-1 series cameras. When an f/2.8 or faster lens is used with these cameras, the baselength of the rangefinding portion of the AF sensor is tripled, thus increasing autofocusing precision.

The EOS-1 class cameras have 7 focusing points out of the total 45 points that become high-precision with f/2.8 or faster lenses, compared to just 1 high-precision focusing point on a 20D, 30D or 5D, and the center focusing point on an EOS-1 class camera has high-precision capability with lenses as slow as f/4, so one could say that the EOS-1 class cameras have a higher level of features. But in terms of autofocusing precision, the 20D, 30D and 5D are equal to the EOS-1 class when comparing the center focusing points of each camera.

Best Regards,

Chuck Westfall
Director/Media & Customer Relationship
Camera Marketing Group/Canon U.S.A., Inc.

Jamoke

In tying it back into your current lenses; You'll see an amazing increase in speed because of the difference in aperature. I have a 18-55, as well as a 70-300 3.5-5.6, and I have the 85 that you were looking at. I was blown away the first time I tried an aperature of 1.8 on my 20D. Try it out though. Plenty of stores cary the 85, 1.8. Just walk in and see if they'll let you slap it on y our camera and take it for a spin. See for yourself if it will give you the speed you expect or need.

wxwax

Jamoke wrote:

Plenty of stores cary the 85, 1.8. Just walk in and see if they'll let you slap it on y our camera and take it for a spin. See for yourself if it will give you the speed you expect or need.

That's the best way to find out if it will meet your needs.

Mitchell

Please forgive my Nikonian ignorance.:hide
Don't the Canon lenses with USM focus faster than the normal lenses regardless of camera body?

The Nikon equivalent is the AF-S lenses compared to standard AF. The AF-S lenses focus much more quickly and silently for me on both my pro body (D2x) and my prosumer (D70).

mercphoto

Mitchel wrote:

Don't the Canon lenses with USM focus faster than the normal lenses regardless of camera body?

Not all USM is created equal. The 75-300 USM will focus slowly on any camera. However the USM in a 300/2.8L is so fast its scary.

It is my understanding that focus speed is dependant BOTH upon the camera and upon the lens. The camera body calculates where to move the lens to. A 1D Mark II is fast in this regard because it has one microprocessor devoted solely to auto-focus, and a second one for all other tasks. But the lens is what is responsible for actually moving the lens element to the calculated position.

ziggy53

mercphoto wrote:

Not all USM is created equal. The 75-300 USM will focus slowly on any camera. However the USM in a 300/2.8L is so fast its scary.

It is my understanding that focus speed is dependant BOTH upon the camera and upon the lens. The camera body calculates where to move the lens to. A 1D Mark II is fast in this regard because it has one microprocessor devoted solely to auto-focus, and a second one for all other tasks. But the lens is what is responsible for actually moving the lens element to the calculated position.

Some camera makers put the focusing motor in the camera. All of the Canon EOS lenses have the motor in the lens. I think there are 5 different motor technologies that may be used in the Canon named lenses, and then each 3rd party manufacturer has there own versions to boot.

I have never seen any scientific method developed for testing the combinations and permutations possible between all the disparate technologies, so for now you have to live with user accounts and opinions, or try a lens for yourself on your own system. That makes for more interesting shopping trips.

ziggy53

ziggy53

OK, I found a document published by Canon. They claim 4 motor technologies are used in Canon lenses. (I could swear I read about a fifth. Maybe I was drinking a "fifth". No, I don't drink, that can't be it. Gosh am I old, maybe that's it. Yeah, that's it.)

Here's what they say,

Autofocus Motor
Designation Description .........Notes
AFD ..........Arc Form Drive ....Original EF Lens motor - compact but slower and noisier than USM lenses
MM ...........Micro-Motor .......Compact cheap motor typically fitted to "consumer" lenses
USM .........UltraSonic Motor ..Ring-type USM lens - the fastest quietest AF motor with benefit of Full-Time Manual focus (see below)
Micro-USM .Micro-USM Motor .Cheaper form of USM (using micro-motor rather than USM Ring) Still quiet but not as fast and does not generally provide FTM. Mark II version of Micro-USM introduced in 2003

P.S. Now I remember. The article I read about classed the Micro-USM and the Micro-USM II as different technologies. Canon just lumps them together. Ring-Type USM is obviously the one that makes the biggest difference with the most benefit.