K100D Autofocus

[alisa_stieg]

While researching sensor cleaning tips on the net, I ran across this quote from the following article (http://www.e-

fotografija.com/artman/publish/article_1154.shtml) and wondered what your thoughts were. I've been trying to

capture a bird in flight for several weeks now without much success. Up to this point, I had been thinking it was my

inexperience with this type of photography, but the following quote now has me wondering: "this camera and lenses

will not be used for taking pictures objects moving at high speed, let alone sports. The autofocus system requires

relatively strong contrast, making the camera hunt for focus for quite some time. The in-camera focusing motor is too

slow to allow capture of fast objects, such as sport. Therefore, when it comes to focus speed, it cannot be compared

with the competition, such as the EOS 350D."

 

Is the autofocus system on the K10, K20, or K200D significantly better than the K100D? I'm not really in the market

to get another camera, but this is becoming a frustrating endeavor! If all the practice in the world won't help me due

to some shortcoming in my camera, it would be good to know about that. On the contrary, if there's something else

I can do to improve this skill, please advise me on that as well.

 

Thanks!

Lisa

[renatoa]

Alisa, search resources about focus trap. This is the main technique to be used with K100D for such situation.

[andrewg_ny]

I will suggest that the AF on the K10D, K200D, and K20D are faster than the K100D but not so much faster that it

will make capturing birds in flight easy. People were photographing BIF before AF was ever available. You may

find results better focusing manually. Things you can try & see what works best for you:

 

<UL>

<LI>Fresh batteries (or maybe disposable Lithiums) will improve AF speed.

<LI>Some lenses are faster than others and hunt less

<LI>Experiment using AF.C, multiple vs. center-only AF points

<LI>Try decoupling AF from shutter release (on K100D you can set the 'OK' button to enable AF via custom setting)

This can allow you to focus first then worry about re-composing

</UL>

[mc2imaging]

You know, we used to capture moving objects before auto-focus.

 

Try hyperfocal or just a bunch of depth of field to cover your margin of error - turn the auto-focus off and stop your lens

down to about f/8 or f/11 and focus in the ball park of your target, or a little shy of infinity.

 

Then, just point-n-shoot!

 

This technique works well for focusing in the dark too... (perhaps Maria will post a pic from our last wedding reception for

me).

[mountainvisions]

Andrew, are we starting to share a brain.

 

What Andrew said.

 

I'd add, lithiums make a huge difference.

 

Lens is a big factor.

 

AF.C using the OK button is a must.

 

Center AF and important....but if the bird is against a flat blue sky, the multipoint will work better because the only thing with contrast in the whole frame is the bird!!!

 

Finally, a lot of these test are done by people that simply expect the camera to come with the best settings.

 

I always point out how Canon pro literature tells the 1DMXX users (and the 1DMXX had been considered THE sports shooting machine for about 5 years) to demap the AF from the shutter, and use singe center point AF.

 

So if the most advanced AF system in the world on a $5000 camera requires tweaking, just think that your $500 K100D might need a little bit of user input.

[jgredline]

I do agree with Andrew and Justin. If I can the reason lithiums work better is because you are giving your Camera the full 6 volts it needs as opposed the 4.8 volts you get from AA rechargeables...I for one have CRV-3 Lithium rechargeables that work great...Also try bumping the ISO a tad. that helps with speed.

[miserere_mei]

So let me get this right, are you guys saying that the photographer actually has something to do with the quality of the photo being taken?

 

Alisa, I was reading the quotes in your post with absolute seriousness until I got to this bit "it cannot be compared with the competition, such as the EOS 350D." I then sprayed my screen with the Sprite I was drinking. Disregard anything this person has written; if any of it is true or correct, it is likely by pure coincidence.

 

Maybe, just maybe, the Digital Rebel XT has a better AF engine. But even if it does, it is not so much better that it will allow you to take sports pictures while the K100D won't.

[renatoa]

Alisa owe you a screen cleaning set ;))

[michael_kuhne]

I certainly do not agree with the quote supplied in this question. The lens, however, often makes a huge difference in speed and accuracy. Justin's recent post regarding the new Tamron 70-200mm f/2.8 is an extreme case in point. But that is very extreme, because as a rule, a well designed faster aperture lens has the capability for faster AF based on more light coming in. Even with the best lens and fastest AF, successfully following and clearly capturing a moving subject magnified through a telephoto lens is anything but easy!! A bird in flight can sometimes be easier than some other moving subjects, if it is not flying irratically or in circles. Often easier than such fast-moving subjects like sports action, which can be both irratic and otherwise unpredictable!! But keep in mind, fast action requires a very fast shutter speed, which unless in bright daylight, will often mean a fast lens! And the more telephoto, the greater the closeup, or the closer the subjects, the harder it is.

 

And yes, using AF-C is a must. Often, with AF-S, by the time you lock in and pull the trigger, the subject has moved enough to have left the focus area that is locked in. Even with AF-C every shot will unlikely be dead on, but more shots will be. Also, especially with the K100, and especially if using continuous shooting mode for burst shots, I shoot fast action in JPEG for quicker processing. But I don't always do burst shooting, and often choose single shot advance with AF-C.

 

Shooting a sport like hockey, for instance, requires dealing with very fast movement from both side to side AND towards/away, in a hard to predict manner. Quite challenging for a photographer, and for any system.. And when's he gonna shoot that puck?? It's so quick!! Here's me, trying to follow the action, eye to VF, wondering just that. Suddenly, SLAP/CLICK!!! Did I get it???

 

Using the K100, I have had very decent success with a fast zoom lens, my Tokina 28-70mm f/2.6-2.8 Pro II. Most of the time I use single shot mode and AF-C. I have been shooting about 150-200 shots per event, and getting somewhere around 50-to 80 that are good to very good, with yet more that are usable. Here are just a couple, shot at ISO 1600 and between 1/350-1/500 sec.<div></div>

[michael_kuhne]

And another..<div></div>

[alisa_stieg]

Michael, I'm glad to hear your response knowing you are a fellow K100D user. I'm curious to know if you've tried the trap focus method that Renato suggested. I've researched it and am intersted in using this method, but am having trouble with my camera set-up. After looking through the user manual and Magic Lantern guide, I'm not finding any directions for this specific action. The best I've come up with so far is directions for a Nikon at the following site; http://forums.dpreview.com/forums/read.asp?forum=1034&message=9479603. Wonder if the AE-L button is the same as what they describe in the Nikon directions. As far as I know, there is no Auto-Focus lock, is there? The manual says that the shutter doesn't release in AF-S mode unless the subject is in focus, but I find this isn't always necessarily so for reasons you've already stated.

 

Lisa

 

Thanks all for the information. I have considered the problem to be the batteries, although even freshly charged ones don't improve the situation to my satisfaction, although they are NOT lithium as Javier suggested.

[michael_kuhne]

I've used a little trap focus with my film models and a MF lens quite some time back, but not yet with a DSLR. The way I worked it was with a cable release set locked on position, with the camera at AF-S. It is a little tricky, but it can work.

[alisa_stieg]

Mis, I'll get that screen cleaning kit right out to you...sorry about that!

[andrewg_ny]

I think you can only use focus trap on a Pentax D-SLR if you have a manual focus lens attached, or possibly a lens like DA* (I can't verify this) that allows the AF to be switched off on the lens body. If you're using a manual-focus lens, and are on AF.S, and have the shutter button pressed, the camera will fire at the moment it locks a subject. Others probably have more information and experience with this--maybe there is another way.

[rogerdaltx]

As far as the focus speed of the k100d goes: over the last 18 months I've owned a Canon 400d, Pentax k100d, k10d and very recently a new k20d. The k100d unquestionably has the slowest focusing and poorest motion tracking of the bunch; lithium batteries or not. Obviously with good technique you can get nice action shots with most any camera, but some cameras require more skill to get the shot. The k10d focuses noticeably faster than the k100d did, especially with a DA* SDM lens, but it's faster with any Pentax AF lens compared to the k100d. The k20d seems to be improved over the k10d in locking low contrast focus; I'm not sure about tracking yet as I don't shoot moving subjects that often. Between the k10d and k100d the Canon 400d was the fastest at locking focus and better by far at tracking moving subjects in servo.

[alisa_stieg]

Andrew, I believe you hit the nail on the head...the switch on the front of the camera needs to be moved to MF, but the AF needs to be on in the camera set-up. The directions I read didn't post that detail, but after pondering it, I came to the same conclusion. If I get time, I'll try this setup today and see what happens. Seems like this would be a good technique for my hummingbird feeder...

[miserere_mei]

Alisa, trap focus doesn't work with AF lenses (maybe it does with AF lenses that have an AF/MF switch on them,

like Andrew said, but I don't have any to test it with). With manual focus lenses it does work, but you need to

do two things:<br>

<br>

1) In the Custom Menu there is a setting so that the camera will only fire if it is in-focus. Switch that on (I

think it's on by default).<br>

2) Set the focus switch on the camera to AF.<br>

<br>

I use this set-up for macro, so I can keep the shutter release pressed and then move slowly forward until the

flower/bug/whatever comes into focus, at which point the camera fires.<br>

<br>

If there is another way to set-up trap focus, I'd like to hear about it, guys!<br>

<br>

Alisa, thanks for the cleaning kit; I'll PM you my address.

[andrewg_ny]

Alisa, I think the camera AF must be set for AF.S (single AF). If on MF, the camera will not wait for focus lock and will trip the shutter immediately.

[alisa_stieg]

Well, I've not had luck with this using my AF lenses so far. The only MF lens I have is 50mm, which defeats the purpose a bit for me. I was hoping to use this method using one of my zoom lenses. If anyone knows how to use this method using AF lenses, that would be AWESOME!