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12-18-2007, 08:41 AM   #1
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AF speed: how much is camera, and how much is lens?

As you already know if you read my "Notes from a 5D experience", I've been very dissatisfied with the AF speed of my K10D + FA43 & FA77 lenses. With the Sigma 18-50 it's a bit better, but still nowhere near the 5D + 50/1.4, 100/2 & Tamron 28-75 I've been trying out lately.

I understand that the FA Limiteds are among the slowest focusing lenses on the K10D. However, I've also heard that the Sigma 18-50 is among the fastest. So, obviously the construction of a lens has a lot to do with how fast it focuses on a camera body. But, the camera body also plays a role in determining focusing speed - as the difference between the *ist and K10D indicates.

My question is, how much can a camera body improve upon a lens's focusing speed if that lens isn't well-constructed for fast AF in the first place? In other words, could the FA43 & FA77 ever focus quickly on a Pentax camera body (such as the new K20D, for example)?

The reason I ask is this: the only reason I haven't sold my Pentax gear and gone with the 5D is that I love the FA43 & FA77, as well as the other DA Limited primes. I'm also as curious as everyone else to see what Pentax announces on Jan. 24th. However, if those Limiteds will never focus as quickly as the 50/1.4 and 100/2 do on the 5D, then I probably just need to move on now.

The DA70 is a bit faster than the FA77, I know, but still fairly slow with AF. Also, it's a half-stop slower in terms of aperture than the 100/2 - which is the equivalent focal length on a K10D. The Pentax 50/1.4, which is the closest to the Canon 50/1.4 in terms of aperture (but not focal length) is also known to be pretty slow with AF, especially wide open.

I guess I'm just thinking ahead to figure out if, even with a new K20D body with faster AF, the lenses I'd want to use will focus as quickly as I need them to.

12-18-2007, 09:54 AM   #2
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QuoteOriginally posted by switters Quote
As you already know if you read my "Notes from a 5D experience", I've been very dissatisfied with the AF speed of my K10D + FA43 & FA77 lenses. With the Sigma 18-50 it's a bit better, but still nowhere near the 5D + 50/1.4, 100/2 & Tamron 28-75 I've been trying out lately.

I understand that the FA Limiteds are among the slowest focusing lenses on the K10D. However, I've also heard that the Sigma 18-50 is among the fastest. So, obviously the construction of a lens has a lot to do with how fast it focuses on a camera body. But, the camera body also plays a role in determining focusing speed - as the difference between the *ist and K10D indicates.

My question is, how much can a camera body improve upon a lens's focusing speed if that lens isn't well-constructed for fast AF in the first place? In other words, could the FA43 & FA77 ever focus quickly on a Pentax camera body (such as the new K20D, for example)?

The reason I ask is this: the only reason I haven't sold my Pentax gear and gone with the 5D is that I love the FA43 & FA77, as well as the other DA Limited primes. I'm also as curious as everyone else to see what Pentax announces on Jan. 24th. However, if those Limiteds will never focus as quickly as the 50/1.4 and 100/2 do on the 5D, then I probably just need to move on now.

The DA70 is a bit faster than the FA77, I know, but still fairly slow with AF. Also, it's a half-stop slower in terms of aperture than the 100/2 - which is the equivalent focal length on a K10D. The Pentax 50/1.4, which is the closest to the Canon 50/1.4 in terms of aperture (but not focal length) is also known to be pretty slow with AF, especially wide open.

I guess I'm just thinking ahead to figure out if, even with a new K20D body with faster AF, the lenses I'd want to use will focus as quickly as I need them to.

With all due respect, why don't you sell your gear and get the 5D.. i started to read your other thread, but it seems like u have your mind made up and are trying to justify it...
First of all what did a K10D cost when it came out?
What did a 5D cost when it came out?
As for the lenses, you will have more of a choice with Canon anyway....
Stop trying to compare apples and oranges...If your looking for speed go with canon...If your looking for quality, then I would say that after looking at Chris's pics and Benjakins, pics as well as many others, then Pentax is the way to go...
12-18-2007, 09:58 AM   #3
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QuoteOriginally posted by jgredline Quote
With all due respect, why don't you sell your gear and get the 5D.. i started to read your other thread, but it seems like u have your mind made up and are trying to justify it...
First of all what did a K10D cost when it came out?
What did a 5D cost when it came out?
As for the lenses, you will have more of a choice with Canon anyway....
Stop trying to compare apples and oranges...If your looking for speed go with canon...If your looking for quality, then I would say that after looking at Chris's pics and Benjakins, pics as well as many others, then Pentax is the way to go...
Actually I'm looking for both AF speed and quality. I could care less about fps - 3 is more than enough.

And no, my mind isn't made up. I prefer the ergonomics, color rendition, and lens choices (though there are fewer) of Pentax to what Canon offers. That's why I am curious about the K20D. However, as you correctly observed, I prefer the AF speed and high ISO performance of the 5D, and I think it's pretty fair to say the IQ of that camera is widely revered.

We'll see what happens in January, but my original question about to what degree the camera or lens determines AF speed is still valid.
12-18-2007, 10:57 AM   #4
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Generally speaking:
- Plastic barrel lenses focus faster than the heavier metal barrel lenses because there is less mass to move
- Lenses with IF (Internal focus) are faster than those without because there is less mass to move
- Lenses with built-in focusing motor are most likely faster than those without

If you compare AF speed you should compare apples to apples, plastic to plastic, IF to IF, etc.

The heavy Limited lenses will never be ultra fast; their quality is in the IQ, the beautiful finish and the suitability for precise, manual focus.

12-18-2007, 11:00 AM   #5
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Put your same lenses on a K100 and you'll see that the K10 focuses a fair amount faster.
However like you said put on a different lens and it'll focus a lot faster.

So they both play a part in the focus speed.

That being said, it sure sounds like your happier with Canon.
So I kind of agree with jgredline.

I prefer Ford over Chevy, so as a result I'll never be happy driving a Chevy.
Does it mean that they are bad vehicles.... No
It just means that I'm better of in the Ford.
Cameras are no different.

I should mention that I could really care less what I'm shooting with, and can get quality pictures out of any camera.
I chose Pentax because I had a few old lenses.
If I start using another brand soon it's because I was offered in insensitive to use it.
12-18-2007, 02:11 PM   #6
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For the record, I completely agree. The truth is that all of the DSLRs out there are capable of producing quality images. What's more, some of my favorite shots of all time have come from a plastic $15 Holga and various other "toy" film cameras.

So, the choice of a camera becomes a matter of determining one's needs and then finding a good fit. When I first chose Pentax a year ago, I was primarily interested in street and travel photography. The compact, high-quality Limited primes were therefore a big part of my decision to get a K10D.

One year later, a lot has changed in my life and I no longer have much time for street, landscape or travel photography. These days kids (my own and my extended family and friends) and people in general are my main subject. And guess what? People move. Kids in particular. So, my needs changed and AF speed and high ISO performance (which weren't that important when I first chose Pentax) are at the top of the list.

Of course it's a valid question to ask why I don't just sell the Pentax gear and get a 5D. Well, I might. But I have to say I've really enjoyed the IQ and colors of the Pentax RAW images; they have a special, film-like quality that people often talk about. I think the 5D is better in this regard than Canon's other offerings, which have a more "plastic" look to them. This is due to the FF sensor, I imagine. But even with manipulation and calibration in ACR/LR, I still don't get quite the look with the 5D that I get with the K10D.

So there you have it. Not an easy decision for me. If it was, I wouldn't be posting this.
12-18-2007, 04:10 PM   #7
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QuoteOriginally posted by switters Quote
Actually I'm looking for both AF speed and quality. I could care less about fps - 3 is more than enough.

And no, my mind isn't made up. I prefer the ergonomics, color rendition, and lens choices (though there are fewer) of Pentax to what Canon offers. That's why I am curious about the K20D. However, as you correctly observed, I prefer the AF speed and high ISO performance of the 5D, and I think it's pretty fair to say the IQ of that camera is widely revered.

We'll see what happens in January, but my original question about to what degree the camera or lens determines AF speed is still valid.
If you collect the SDM lenses that are suppose to appear real soon now (or the ones aalready
on the market, focusing speed is not an issue.
12-18-2007, 05:50 PM   #8
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QuoteOriginally posted by Ole Quote
Generally speaking:
- Plastic barrel lenses focus faster than the heavier metal barrel lenses because there is less mass to move
- Lenses with IF (Internal focus) are faster than those without because there is less mass to move
- Lenses with built-in focusing motor are most likely faster than those without

If you compare AF speed you should compare apples to apples, plastic to plastic, IF to IF, etc.

The heavy Limited lenses will never be ultra fast; their quality is in the IQ, the beautiful finish and the suitability for precise, manual focus.
All these points are true and I'd also like to add the following;
  • Gearing. A lens that is geared for precision (usually manual) work will require more "turns of the wheel" to reach a given point than a lens that is geared for speed. The Limiteds fall in the former group, although anyone with extensive macro lens experience would probably consider them relatively fast.
  • Power. The larger and more efficient the power source (battery usually), the faster it can move the lens. Older batteries tend to degrade over time and the focus speed will degrade with them.

Your Limiteds will never be speed demons, so if you're hanging on in the hope that the K20D will somehow make them perform differently then I'm afraid you may be disappointed...

I use AF for approximately 1% of my photography (and I could probably live without that) so if the K20D was MF only it'd be no skin off my nose - I too happen to love the look that the Pentax Limiteds give me and would only move if I could afford to stump up for a Leica M8 and a choice selection of lenses (not likely to happen in this lifetime). It sounds like your priorities are different though so make the move - there's no point sticking with a system that no longer suits you when there are others out there that do.

Just my $0.02

12-18-2007, 05:53 PM   #9
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QuoteOriginally posted by switters Quote
I prefer the ergonomics, color rendition, and lens choices (though there are fewer) of Pentax to what Canon offers. I think it's pretty fair to say the IQ of that camera is widely revered.

It doesn't matter how low the noise is, or how fast the AF is on the 5d if the colors suck. Personally, I hate the look of 5D skin tones, and reds. Being that it is the curve, it doesn't matter how you set up ACR, the color IQ is just passable compared to K10D results.

But if your taste sees some kind of dreamy quality to the look of 5D images, then get it. We've all seen Ricehigh's photography, and quality of artistry has vastly improved with his 5D. And he found it a pittance to afford. What's a few thousand dollar difference if you found it pretty easy to aquire that kind of money - so get it!
12-18-2007, 07:00 PM   #10
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QuoteOriginally posted by mutley Quote
It doesn't matter how low the noise is, or how fast the AF is on the 5d if the colors suck. Personally, I hate the look of 5D skin tones, and reds. Being that it is the curve, it doesn't matter how you set up ACR, the color IQ is just passable compared to K10D results.

But if your taste sees some kind of dreamy quality to the look of 5D images, then get it. We've all seen Ricehigh's photography, and quality of artistry has vastly improved with his 5D. And he found it a pittance to afford. What's a few thousand dollar difference if you found it pretty easy to aquire that kind of money - so get it!
Well, I definitely prefer the colors of the K10D but I wouldn't say the 5Ds suck. It's all subjective.

The K10D isn't working for me, so I'm not comparing the 5D against it. I'm comparing it against the K20D. That's silly, I know, because it doesn't exist yet. But there seems to be a general idea that it will cost about $1200-$1400. That's not "thousands" less than a 5D - they're available for as little as $1900 new and I regularly see them for $1700 on FM. The lenses I'm interested in aren't expensive: 50/1.4 for $300ish, 100/2 for $400ish and 28-75 for $300ish. Equivalent Pentax lenses would be just as much or more.

So really, we're not talking about a huge price difference here.
12-18-2007, 07:02 PM   #11
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QuoteOriginally posted by rvannatta Quote
If you collect the SDM lenses that are suppose to appear real soon now (or the ones aalready
on the market, focusing speed is not an issue.
I'm really interested in the DA55 SDM. Anyone know when that is supposed to be released?

I wish they'd come out with a DA85 f/1.8. Not likely though, since there's already a DA70.
12-18-2007, 07:13 PM   #12
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Switters, can you borrow a Sigma 17-70 and try it out?
It AFs pretty fast on my K100D so should be even better on a K10D.

Sure not the same iq as the Limited primes but plenty good for family/children snapshots.
12-18-2007, 07:17 PM   #13
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QuoteOriginally posted by Kguru Quote
Switters, can you borrow a Sigma 17-70 and try it out?
It AFs pretty fast on my K100D so should be even better on a K10D.

Sure not the same iq as the Limited primes but plenty good for family/children snapshots.
I have the 18-50. It's pretty fast - the fastest I've tried on the K10D, including: DA14, DA21, FA35, DA40, FA43, FA50, DA70, FA77.

I guess if the K20D has significantly improved AF, and I combine that with the DA70, I could be okay.
12-18-2007, 07:28 PM   #14
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QuoteOriginally posted by switters Quote
I have the 18-50. It's pretty fast - the fastest I've tried on the K10D
I think the 18-50, being 2.8 constant, has much larger glasses & inertia than 17-70.
Based on my 17-70 experience, if Can*n is faster then there's only room for a little faster, impossible to be significantly faster.
12-18-2007, 07:49 PM   #15
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The problem is, I need that constant f2.8 aperture for portraits.
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