Autofocus speed - is there a principal difference with/without built-in-lens motor?

[tomas_telensky]

Is there any principal difference between the focusing speed of lens

with the built in motor and without it? This question is NOT about

ultrasonic motors at all - this is a way different class.

 

For example - Minolta's autofocus is driven by the motor in the body,

and the motion is transfered mechanically to the lens. On the other

hand, Canon EF lens of the EOS system all have the built-in motor,

including the cheapest ones.

 

What concerns me is the comparison of the performance of mechanical

transfer, used by Minolta, and the performance of built in motor. Is

the motion faster in either case? Any ideas?

 

 

It is known fact that Dynax (Maxxum) 4, Dynax 5 and Dynax 7

outperformed the other brands in the same class. In 2000, Dynax 7 was

the fastest autofocus in the world. How is it possible? One would

expect the built-in motor system to be faster.

 

I'm going to buy Maxxum 7. It's focusing speed with 24-105 IF lens

will be fast as hell, I'm sure. But what about using this mechanical

transfer system with a really long glass, like Sigma 170-500 RF? The

RF focusing element of Sigma will be probably significantly heavier

than the IF element of 24-105. Is it still comparable to lens with

built-in motors (non USM of course)? Do you have any experiences with

that?

 

Thanks

 

Tomas

 

 

P.S.: Or could the bottle-neck of autofocus speed be somewhere else

than in the motor speed? Probably not, because faster USM motors make

a big deal, and so do the IF/RF focusing systems with lightweight

focusing element.

[rob_murray]

Well maybe minolta could claim fastest AF with something like

a 50mm lens.Stick a 600mm (if minolta even makes one) on there

and see how fast it is. Not only do the motors have to move fast, they have to stop fast and have enough torque to move the elements.Canons motors in the lenses are optimal for that particular lens. Nikon liked the idea so much they started putting motors in lenses too..

[steve_dunn2]

<p>As far as the mechanics, it's really as simple as how much torque the motor produces vs. how much mass it has to move. Some of Canon's lenses have lightning-fast AF; others are very slow - there are even a couple of lenses with ring USM (the best type of AF motor) which are brutally slow to focus because the optical design of the lens requires the motor to move most or all of the lens elements rather than just one or two groups. I have no idea how strong the AF motor is in the Maxxum 7 but there's no inherent reason why an in-body motor couldn't be quite powerful.</p>

 

<p>I take it you're also familiar with some other things which affect AF performance, irrespective of motor, such as lens speed and the speed with which the body's AF system determines how to achieve focus.</p>

[fmueller]

<i>600mm (if minolta even makes one)</i><p>

 

Thanks, Rob, for including this qualifier into your post. If it wasn't there, an unsuspecting reader might think your comment was based on knowledge, not prejudice ;-)</p>

 

http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=35208&is=USA

[Jochen_S]

O.K. there's a Minolta 600mm. Have we got a performance compairing test against EOS?

I don't know any Minolta more sophisticated then the old 5000. But I use Pentax. I had a body with broken AF motor. - I'd have prefered a broken motor in one lens only. If I remember complaints about power sucking 400mm EOS lenses, so I believe putting the right motor in each lens makes lensconstruction easyer. I doubt my Pentax AF motors could deliver enough torque to move a very conventional telephotolens like my Russian 1000mm. Manual focus override at any moment isn't offered by camera motor AF too, as far as I know. The design of my 100mm macros focusing ring seems optimized for AF, so it delivers a acceptable focusing speed but isn't funny with manual focusing. At least it has a own AF of lever and a additional focusing ring brake for manual focusing. Twisting a af motor without operating 2 switches before should be nicer.

On the other hand: What are we thinking about? You like a 24-105 lens; when you ever need a 600mm f4.0, buying a middleclass EOS body to mount it on will be peanuts.

Something to follow: You quoted a test from 2000 and also limit it to consumer class bodys. The Dynax 7 has no real pro ambition according to Minolta nomenclatura. So what's about the cameras used by pro sports photographers?

Fast as hell is a quite personal point of view. A old digicam has a shutter lag leaving you time to shave and smoke a cigarette not even rolled when you start pressing the shutter. 0.1 sec might count a lot, if you are interested in portraits or sports, so there is still room for improvement... Why do you let out the USM lenses? Get what you can. Don't fear 3 bodys out of 2 camera systems. If you like the Sigma 170-500; mount the best body you can find for it, especially if you are able to change film midroll with both cameras. I myself have been dreaming of a Tamron 180mm macro, but I fear I might waste it on Pentax.

[ron c sunshine coast,qld,a]

That oft quoted marketing drivel really bugs me- "Each lens can have the right size motor"

<br>What rubbish canon!

<BR>Are they really trying to claim that their lens (pick any model) will focus quicker than a competing motor-in-camera design...if the camera focus drive motor is twice(or more!) as powerfull?!

<BR>Ok,they only make the focus motor in the camera so big (depending on the model body) but the "right size motor for each lens" is all to do with economics and marketing- very little else.

 

 

 

 

<p>Tomas,the minoltas *claimed* to have the fastest autofocus in the class...but at the very same time i saw canon advertising claiming the very same thing!

So we know that none of them can be trusted to give the absolute truth so we'll have to rely on independant reports.

<BR>Sadly there is a lack of anything comprehensive on this subject.I've seen occasional reports of nikon(mechanical drive) beating canon (usm) in certain classes of body /lens combo..but no other claims of nikon being better so we can assume that nikon are very close/better in some areas but probably a fair bit slower than canon over the whole lens/body range.

<p>I'm guessing (from 2nd hand reports) that minolta are in a similar situation

<P>I must say that this whole USM thing is way overblown.

<BR>In the better grade lenses- used with a good body-USM is genuinely VERY quick.This is mostly because a true ring USM motor is slightly more efficient(or so i've read)...and gains a little more efficiency by having no drive gears.

<BR>The 'USM' on the consumer lenses is mostly just marketing drivel.Compare a consumer USM lens to a normal micromotor lens and you'll mostly find them to have near identical focus speeds!

<BR>I've tested many cnosumer zooms' focus speeds and could only really recommend buying the usm version is the lens needs every little extra bit of focus speed it can get (such as the 75-300 models)

 

 

<P>Hope these comments make sense-i wrote two seperate parts and just lumped them together....

[rokkor fan]

Some brief comments for Jochen

 

"O.K. there's a Minolta 600mm. Have we got a performance compairing test against EOS?"

 

Yes, it's on a par with EOS and Nikon, refer:

 

http://www.wildpicture.com/pages/photography/teletest.htm

 

"I don't know any Minolta more sophisticated then the old 5000."

 

OK, so you are talking like an authority and all of your information is based upon a consumer model camera (not even the top of the line) released in 1986. I'm sorry, wasn't that BEFORE the first EOS body was even released! (March 1987). Surely Minolta can't have advanced any further in AF technology since then!

 

"But I use Pentax. I had a body with broken AF motor. - I'd have prefered a broken motor in one lens only."

 

Sure, and if this were a discussion about Pentax bodies your experience in this respect may be worth something. How many Minolta cameras have you heard of that have had their AF motor break down? Really, have you heard of any?

 

"I doubt my Pentax AF motors could deliver enough torque to move a very conventional telephotolens like my Russian 1000mm."

 

Well, thanks again for that vote of confidence for Pentax. perhaps you should remotely consider that you don't know anything about the Minolta AF system.

 

"Manual focus override at any moment isn't offered by camera motor AF too, as far as I know."

 

Well, you know wrong. That may be the case with the 1986 5000, but the Maxxum 7 has a AF button on the rear - similar to the EOS 1v using CF4-1. Very handy, and means no expense on FTM lenses. Perhaps you should do a little research? Refer:

 

http://www.photo.net/equipment/minolta/maxxum7

 

"The design of my 100mm macros focusing ring seems optimized for AF, so it delivers a acceptable focusing speed but isn't funny with manual focusing. At least it has a own AF of lever and a additional focusing ring brake for manual focusing."

 

More not applicable Pentax issues.

 

"Twisting a af motor without operating 2 switches before should be nicer."

 

Oh, like the Maxxum 7 (Dynax 7) enables? Yes you may be correct!

 

The Dynax 7 has no real pro ambition according to Minolta nomenclatura.

 

Do you have any idea whatsoever what you are talking about? It is the most technologically advanced Minolta AF body. That's like saying that no pro's will use an EOS 3 because it doesn't have a 1 in front of it.

 

"I myself have been dreaming of a Tamron 180mm macro, but I fear I might waste it on Pentax."

 

Why? Because a Pentax would take a different picture with that lens to an EOS or a Minolta? Do you think for a minute that when shooting in macro that the film body will make any difference at all to the image?

 

OK, now all that has been said, here's the answer to the main question.

 

The Maxxum 7 (Dynax 7) is an outstanding camera, and the in camera AF is very fast. However, the test where it was fastest was with a 50mm. At super long lengths it will AF slower that lenses with USM or SSM. That said, Minolta are now releasing these lenses. For shorter lenses it will be as fast or faster than an equivalent Canon.

 

When you consider the price (US$400 at B&H a month ago) it provides incredible value, particularly when cameras like the EOS 3 don't include all of its features. The back LCD used in the 7 has just been picked up by Nikon for their F6.

 

Just for the record, the only AF cameras I own are a EOS3 and EOS 1v. Canon is a better choice if you want long glass, not because of the quality of the Minolta lenses (which are excellent), but simply due to economics. Canon sell more, hence there are lower prices on super teles enabled by longer production runs. Also, Canon keep parts for these lenses worldwide due to the requirements of the pro users. With Minolta a 600mm is a rarity, and you may wait for a service for some time.

 

Finally, the bigger market means your 600mm will be more saleable if you ever choose to sell it.

 

That's why Canon is the best choice for super telephotos. However, for other uses the Minolta is a great alternative, and with the new 7D with in body IS it may even be superior if you plan to shoot digital.

 

Cheers,

 

Antony

 

 

 

[rokkor fan]

Jochen,

 

Sorry, that response was a bit rude - I apologise. But seriously, that sort of disinformation makes me pretty mad. That's why I responded as I did.

 

Regards,

 

Antony