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Old Feb 11, 2009, 4:49 PM   #11
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Thanks danielchtong, I'm going to look into the DA*300mm with the SDM.
I love shooting BIF shots, but my success rate has been pretty low,
maybe 1 decent shot out of 50. Hmmm, not too good, but hopefully things
will improve, since I'm now using a cheapo Tamron 70-300mm lens.
I wish Pentax would come out with a faster focusing dslr, and maybe something with 5+ FPS. I love my K10D, except for the slow focus and slow fps. Oh well, maybe they'll release a Pentax 30D soon with better speed.

Cheers,
flyshooter :|
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Old Feb 13, 2009, 5:34 AM   #12
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flyshooter wrote:
Quote:
Thanks danielchtong, I'm going to look into the DA*300mm with the SDM.
I love shooting BIF shots, but my success rate has been pretty low,
maybe 1 decent shot out of 50. Hmmm, not too good, but hopefully things
will improve, since I'm now using a cheapo Tamron 70-300mm lens.
I wish Pentax would come out with a faster focusing dslr, and maybe something with 5+ FPS. I love my K10D, except for the slow focus and slow fps. Oh well, maybe they'll release a Pentax 30D soon with better speed.

Cheers,
flyshooter :|
Looking back I would say the following:

*compared with bif, this is probably easier as the the background lacked contrast and it is easier for the camera/sdm combo to track. When some branches happen to be in between, your focus could sudden snap to the non-subject - the image is waste (OOF)
*subject is fast but a lot more sizeable compared with a bird.
*subject movement is predictable and you can do trial runs. bif is erratic at best. Ensuring that the bird within your viewfinder is difficult already. When it is out there is no way you can track.

Before doing bird in flight, it is better off to know the limit of your camera/lens . Track-focus some slow moving vehicle going sideway (all predictable) would be a good start to fathom the limit


Daniel
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Old Feb 13, 2009, 1:00 PM   #13
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Just thought I'd jump in. First off, nice shots. I full expect to see you down in the sports forum now Daniel.

But I wanted to mention a few things about shooting subjects in motion - wheter it's sports or BIF with AF.

1. The biggest issue that causes people problems in either category is trying to photograph something that's too far away. In my experience there are 2 parts to this - part 1 how big your subject is and part 2 the limitations of the lens/focus system. In general the more of your subject filling the frame the better chance you have at focus success - it's true of one shot but especially true of continuous focus since the camera constantly tries to re-focus. This first part is what causes problems for small birds - the bird may only be 10 yards away but it's so small the camera just can't get a good focus. But the other part - the lens/focus part is what causes problems with some larger subjects. My experience is with Canon but I'll bet this carries thru in other systems as well - a lens is really only designed for critical focus within a certain range. Beyond that range you're simply not going to get good focus. For instance, when I put a 200mm lens on my 1.3 crop camera I get accurate focus out to about 25-30 yards for a moving person. When I put it on my 1.6 crop camera it doesn't 'extend' the focus reach. It really doesn't. If anything I lose a couple yards of accuracy because the focus system on the 1.3 crop camera is better. Or, another test I've done - my 70-200 at 70mm focuses better at 30 feet than my 85mm prime. Why? My GUESS is it's the focus mechanism on the lens. At 30 feet the 85mm lens is near infinity while the 70-200 is about half way. So in my experience you need to stay within the LENS' performance limits. To those shooting BIF, 300mm is not very much reach - if you're having problems focusing it is very possible the bird is too far away and not filling up enough of the frame.

2. Learn how your camera determines focus. For Canon it uses contrast. So you need a contrasty part of the subject to keep the focus point on. So, when I shoot sports if a person has an all white jersey that's really bad contrast so I don't use the jersey to focus on. So, do some research on how Pentax cameras determine focus - if it's contrast based you want to be sure your focus point is on an area of contrast.

3. Learn about the focus points of your camera and the technology involved. Again, I'm not that familiar with pentax but in Canon there are really 3 types of focus points. A basic point that recognizes contrast differences along a single axis. A cross-type point that can recognize contrast differences along either axis and high precision points that contain an extra sensor that provides more accurate focus with lenses that have a certain aperture value or better (typically f2.8 or better). In that system it's important to know these things - and know which points on the camera are which type. For example in the 40d only the center (of 9) focus points is high precision. So many sports shooters will use only that center point. When shooting with an f5.6 lens however you get no benefit from the point so the center is no more accurate than the other 8 (which are all cross type) - on some other models only the center was cross-type. And on 1-series there are 19 high precision cross types to choose from. My point here is - do some research on Pentax and how their focus points are set up. I don't know if they have similar technology differences. But these types of differences can be important. And you should learn what they are in your system so you can take advantage of them.

4. Recognize how DOF comes into play. Realize that as you use longer focal lengths and wider apertures you run into situations where your entire subject may not be in focus. In such cases you want to be sure you're focusing on the part of the subject you WANT to be in focus. This is a reason why many wildlife shooters will use a single focus point for BIF - if there isn't enough DOF for the wing tip and face to be in focus you don't want a focus point on the wing tip determining your focus you want a focus point on the head deterimining it. So you use a single point only to lessen the chance of the wrong part of your subject being in focus.

5. Realize how predictive focus works. In most DSLRs, continuous focus isn't just constantly refocusing, it's PREDICTING where to focus to speed up the process. So, when there are sudden changes in direction focus failures occur. The better the focus system the quicker the recovery. But in any camera you have better odds at success if you track a subject along a constant path for at least a second before firing away.

AF and continuous focus are no different than any other component of photography - it doesn't just magically work all the time. The best success is when you understand how the various components are implemented in your camera/lens and utilizing those to the best advantage (e.g. if I were shooting with a canon 40d and a 2.8 lens I'd use center only focus point because it's the most accurate - if I were using an f5.6 lens and my subject was fully and completely within the focus plane and there weren't other potential misleading subjects I'd use all focus points to give the camera the best opportunity to find contrast). In the end, equipment will make a difference but the above info can be applied to any system / camera to help you get the best results with the equipment you do own.


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Old Feb 14, 2009, 1:06 PM   #14
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JohnG wrote:
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5.┬* Realize how predictive focus works.┬* In most DSLRs, continuous focus isn't just constantly refocusing, it's PREDICTING where to focus to speed up the process.┬* So, when there are sudden changes in direction focus failures occur.┬* The better the focus system the quicker the recovery.┬* But in any camera you have better odds at success if you track a subject along a constant path for at least a second before firing away.┬*
John

Thanks for the detailed input.
Pentax did not have SDM that long and predictive focus tracking with vanilla screw motor is very tricky if not impossible.
There is very little reference of focus tracking in most Pentax forum even though it is quite well known in the Nikon/Canon groups
The most conventional method for doing fast Pentax action has been 'focus trap'.
Well at least it is a good start with a couple of SDM lenses.

Daniel
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Old Feb 15, 2009, 2:01 AM   #15
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I've given up on autofocus for fast moving things. I would have to spend a lot more on a better autofocus system than what I have on my DL. But with manual focus you can usually get some pretty good shots especially using the focus trap method mentioned by Daniel. John, thanks for the detailed explanation of autofocus.

Glenn
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Old Feb 15, 2009, 6:55 AM   #16
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i must say ive been quite impressed with the continous focus on the K20D

that was one of the things i wasnt expecting and it allmost stopped me buying one, i liked the sound of the inteligent tracking on the nikon D300, but in the end it was a price issue with me, so when i started using it to photograph horses mainly, ok not the fastest of moving subjects, but still moving quite fast. The first time i did it i just set the camera, continuos focus and burst mode, held my finger on the shutter and panned, i was hoping for a few a good shots at best, but when i uploaded them to the pc i had about 3 shots out of focus out of about 40.

now theres no way in the world it was down to my brilliant photography skills lol, so ill just say thanks pentax for making me look good

nice pics btw daniel
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Old Feb 15, 2009, 3:46 PM   #17
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kazuya wrote:
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i must say ive been quite impressed with the continous focus on the K20D

that was one of the things i wasnt expecting and it allmost stopped me buying one, i liked the sound of the inteligent tracking on the nikon D300, but in the end it was a price issue with me, so when i started using it to photograph horses mainly, ok not the fastest of moving subjects, but still moving quite fast. The first time i did it i just set the camera, continuos focus and burst mode, held my finger on the shutter and panned, i was hoping for a few a good shots at best, but when i uploaded them to the pc i had about 3 shots out of focus out of about 40.

now theres no way in the world it was down to my brilliant photography skills lol, so ill just say thanks pentax for making me look good

nice pics btw daniel
Honest to God I like to have zero electronics in my lens. My A*300mm made in late 80s is still going strong. There is no way that the new batches of SDM equiped lenses surviving that long. But having said that I still think for fast actions there is no alternative but to use sdm lens for that critical speed of split second for the lens to respond. Relying on old screw motor (in camera) to drive the lens to the focused position in split second just will not work even for 3 fps not to mention the top of the line (10fps of Canon+Nikon) performance.

Also as you have said , you did not do much . And if you can get things in focus you can only hope the next K20D Super can get you better images. Basically you can only improve by upgrading your gear.

In doing manual focus for fast action shots, I have only myself to blame if I cannot make it.

Daniel
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Old Feb 17, 2009, 11:18 AM   #18
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does anyone know ifthe sigmaHSM lenses work as well as the SDM pentax ones for speed and focusing?
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Old Feb 17, 2009, 6:51 PM   #19
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kazuya wrote:
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does anyone know if┬*the sigma┬*HSM lenses work as well as the SDM pentax ones for speed and focusing?
They are very new

http://forums.dpreview.com/forums/re...ssage=31015870

And Pentax does not have a 70-200mm SDM lens yet to compare with the Sigma's counterpart


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Old Feb 17, 2009, 7:10 PM   #20
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Let me add - assuming the HSM operates the same in Pentax mount as it does in Canon or Nikon I would be amazed if it's not as good as the SDM. I've owned the Canon mount and it was very close in speed to the Canon 70-200 2.8 I now own. Having used DSLRs of different levels I would guess the camera's AF system will be more of a limiting factor than the HSM. My sigma was absolutely up to the challenge of the 10fps of my current camera. Keep in mind though, that's the 2.8. Even with HSM, a f5.6 lens is going to have issues in lower light. But again, that's not a fault of the focus motor - just not enough light getting in for focus.
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