The DA55 on the K-7

blende8 · 05-30-2009, 09:45 AM

Reports noted that DA* lenses are focussing faster on the K-7.
I tested this yesterday and cannot really confirm that.
The K-7 may be minimally faster, but it's not much, if at all.

Here are two videos, I did (each about 7MB).
The camera focussed to the opposite quay wall, almost infinity.
K-7
K20D
Judge for yourself.

*ytterbium* · 05-30-2009, 10:06 AM

Nice video you have made. Even if the difference is small you can clearly see it. It may not seem to be a lot, but it shows that the focus has been really improved and even its fundamental operation (basically just turning the lens) is faster. This hints that it may be even more faster in a situation where it can truly show itself.

Are you also able to do some high iso, low light samples? I believe those would be very welcome to the forum.

But i must object on such way of testing. It seems as the test has been done under good lighting and cameras standing still (on the ground not in hand). This allows for both cameras to instantly measure phase offset (since the subject is well lit and not moving) and kick the lens to that point. This means that only thing determining the lens speed would be its mechanics/motor and the juice (camera battery) it is supplied with. Maybe a little fine focussing when near the subject.

Maybe (but unlikely.. this usually seems to happen at the first approximation unless the camera starts to hunt at beginning) some cameras check the measured distance while turning the lens (as with some tracking/continuous AF, but it seems that Pentax cameras check distance with lens still, then turns it again) and this could slow the turning a bit, for distance calculation to catch up (like stepping the lens and checking instead of going directly to finish). Unlikely.. i bet it is a hard-wired logic which can calculate distance reading instantly (compared to mechanic speeds).

If the DA55 was focussed by screw then there could be a chance that there is a new, faster (stronger) motor in camera. Otherwise it can only calculate required focus throw more accurately and faster in worse conditions than k20d could, since the physical maximum rotation speed is determined by lens (you cannot drive a 5V motor with 30V, you'd burn it or break the gears).

Just my humble opinion. But it seems that the new battery is doing good. Was it fresh or had been used for some time already?

tcom · 05-30-2009, 10:14 AM

I had the chance yesterday to handle a bit a K7 (in firmware 0.20) at a photo fair (Professional Imaging in Zurich). The DA55 was on the K7 and I tried how the camera focuses. It was indoors, in rather poor artificial light, the K20D would probably have hunted a bit, but this K7 moved the DA55 accurately to the correct spot and locked immediately.

blende8 · 05-30-2009, 10:27 AM

You may be right.
It is difficult here to do a quick, scientific test.

The K-7 may be slightly faster.
But not that much faster, that I would say "Wow".
I can only say that with the DA55 I had difficulties to see a difference.
I did several tests.

High ISO samples?
Yes I have some, but they are not nice.
The K-7 showed more noise than my K20D.
But it had an unknown early firmware on it. It showed "0.00".

*ytterbium* · 05-30-2009, 10:51 AM

Oh well.. i believe then those doesn't count

.
I mean now days cameras have so few physical differences and so many software "features" that you cannot even say you've handled K-7

. Just a carcass

.
Btw, what colour the AF assist light has, green?
It would be cool to have an AF assist light that projects "PENTAX" in red, lol.

I wonder why camera manufacturers dosn't sell camera software yet.
How mane physical differences all istD's and k1x0d had.. imagine getting "new camera" for half/third the price in a SD card

. How much does it cost to manufacturer...ah the piracy would spoil it all.. right

. OK, sorry for the off topic.

*dugrant153* · 05-30-2009, 02:06 PM

Thanks for posting that! good to know for my future purchases.

I'm not sure why people are calling the DA*55 slow. In these videos it looks to go from one end to the other pretty fast. The way people talk about it, it's like it takes forever to go from lock to lock. Good to know there's some improvement with the K-7, even if not much.

Honestly, I think I'd be more concerned about the lens getting the focus right and in a reasonable amount of time. I've missed critical shots b/c my lenses would take too long trying to focus and sometimes would simply not lock. I'm hoping the K-7 gets way better accuracy cuz to me that would mean a lot more than the lock to lock speed.

*Wheatfield* · 05-30-2009, 02:33 PM

Originally Posted by dugrant153

I'm not sure why people are calling the DA*55 slow.

I compared my DA*55/1.4 to my FA50/1.4 for lock to lock speed on my K20.
The FA is about 3x faster at ~1/3 second compared to the 55's ~1 second.
To me, that is slow, very slow.

sean · 05-30-2009, 03:39 PM

The DA* 55 is slower, but the colour rendering, contrast, and overall IQ are much better than the FA, IMO. Pretty sharp at wider apertures, too.

I'm really happy with this lens.

I hope they do a 30mm weathersealed SDM soon.

**roentarre** · 05-31-2009, 12:09 AM

Mmmm, the only advantages of k7 over k20d seem to be not all that different from each other.

Thanks for this report. I will spend my money elsewhere.

PentaxPoke · 05-31-2009, 12:40 AM

Originally Posted by Wheatfield

I compared my DA*55/1.4 to my FA50/1.4 for lock to lock speed on my K20.
The FA is about 3x faster at ~1/3 second compared to the 55's ~1 second.
To me, that is slow, very slow.

Wow, that is just inexcusable considering that the FA was designed in the film era! I'll bet its that doggon SDM slowing things down again...

Thanks for the videos blende8. I don't care what anyone says about the validity of the tests. It clearly shows the limit-to-limit speed of the lens on both cameras, and they are almost exactly the same to my eye. I'm sure both cameras were supplying the appropriate power to the lens driving it as fast as it could go.

As I have said before: I think that after the k-7 comes out, we won't be complaining about the AF speed of our cameras any longer. We will be complaining that the focus speed is limited by our lenses using Slow Drive Motors.

yipchunyu · 05-31-2009, 03:47 AM

when I heard the news about faster AF speed with K7 (da 55). I asked the same question, as if it's sdm lens, why and how the af speed be a lot faster with k7.
some other answered the question and told that it's because the new battery.
Don't know whether it's true or not. just hope that k-7 will make sdm lens a lot faster. I have a da 300 and really hope the af speed can be improved.

Mystic · 05-31-2009, 09:18 AM

Personally I do not see in this video any indication, that K7 with DA*55 is faster than K20d..

*ytterbium* · 05-31-2009, 10:03 AM

Originally Posted by Mystic

Personally I do not see in this video any indication, that K7 with DA*55 is faster than K20d..

I did a dumb, little and useless measurbation.
For each camera i've stopped the video frame before (in the next frame lens has already has turned) or after (in the next frame lens stays the same) the lens starts to move/stops, so this may be a quite inaccurate. Results:
93-69=24 for K-7,
42-18=24 for k20d.

Class A · 05-31-2009, 05:45 PM

Originally Posted by roentarre

I will spend my money elsewhere.

I don't think a single test with a firmware "0.00" can be decisive.

Also, I'm surprised to hear that all the other improvements/additions in the K-7 do not concern you. You are only after improved AF?

Originally Posted by yipchunyu

if it's sdm lens, why and how the af speed be a lot faster with k7.

This is pure speculation but next to a stronger battery it may also be the case that SDM speed depends on how the camera drives the SDM motor. The speed of stepper motors depends on the frequency with which they are driven. No idea whether SDM is similar in any way and in the absence of that knowledge I'm free to speculate that SDM speed need not be exactly the same.

PentaxPoke · 05-31-2009, 06:09 PM

Originally Posted by Class A

This is pure speculation but next to a stronger battery it may also be the case that SDM speed depends on how the camera drives the SDM motor. The speed of stepper motors depends on the frequency with which they are driven. No idea whether SDM is similar in any way and in the absence of that knowledge I'm free to speculate that SDM speed need not be exactly the same.

I don't think they are steppers. I think they may be servomotors.

I also believe that it is wishful thinking that firmware updates will improve how fast SDM works on the K-7. I'm going to get a K-7, but I'm sticking to screw drive lenses. I'm glad the're not putting that SDM in the limited lenses!