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Old Jun 9, 2007, 6:32 AM   #11
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Corpsy, thank you for sharing this technique. Your gull shots are really great. I began playing with it yesterday afternoon, and right now have nothing worth showing from it, but I did get it to work with three of my manual lenses.

John Hill was speculating that it might not work with "pre-A" manual lenses, but I did get it to work with an old Vivitar 75-250, although I did run into one problem.

I was trying to focus on a great blue heron in flight at a pretty good distance. With the weight of the K10d with grip and the heavy lens (this thing is old and HEAVY), I had difficulty holding the focal point accurately enough to make the trap work.

I think the point simowills makes is a good one, though. For those of us old enough to battle visual acuity problems, the technique can be a valuable one. I like to shoot that Vivitar lens with a Sony VCL-HGD1758 telephoto lens (1.7X) on the end of it. The weight combination makes it strictly a tripod/monopod proposition, although it produces good results. Focusing has been the problem I've had with that combination, so I can't wait to get out today and see what I can do with the focus trap with that combination.
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Old Jun 9, 2007, 8:14 AM   #12
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thanks to all who explained how this teqhnique works
i finally got my ds to do it
i had to change it from contious focus to single (AF-S)
i will try to give it a whirl tomorrow
i also found if a put a 2x convertor on my auto focus lenses would do the trap thing too

Corpsy your photos here are inspirational

thanks again everyone

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Old Jun 9, 2007, 9:26 AM   #13
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Can I conclude ....that "focus trpping" will work only with a manual lens and the camera in the auto focus mode, and not with an auto focus lens set in ythe manual mode?

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Old Jun 9, 2007, 2:03 PM   #14
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Feroz - you are correct. If the camera is set in manual focus mode -no matter what lens is on it - the camera will take the picture, regardless of what the AF mechanism says.
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Old Jun 9, 2007, 11:41 PM   #15
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John Hill wrote:
Hmmmm, I dont think it will work with every manual lens on every model of Pentax DSLR. I can get it to work with an 'A' lens on my *ist DS but not with any other type of manual lens I have. I have seen reference to shorting out the electrical pins to make it work with other lens but although I tried and tried I had no success doing that.
Having recently gotten my first K M lens yes it will and can't see why it wouldn't for M42's either.... camera knows there is a lens there but not what it isthe CP limited AF still functions.

And I will qualify this for the K10D.... likely the K100's too..... older isT's I can't say.
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Old Jun 10, 2007, 12:39 AM   #16
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Sorry for not responding sooner, I had a complete Windows meltdown and have just now gotten things more or less up and running.

Thanks for all the compliments! I was very happy with how these turned out, and they are definitely the best bird in flight shots I've taken. I just hope that this practice pays off when I try and capture something a bit less common.

To answer a few questions, the lens used was completely manual. I usually find it's best to try and underexpose a bit when using this kind of lens. I was shooting in M mode of course.

I'm not 100% sure I remember the settings I used, but I believe most shots were taken at f/8 at 200mm, though at some point I set it to f/11 and turned up the ISO. The f/stops are printed on the lens with 8, 11, and 16 in colors. I thought it was indicating that 11 was it's sweet spot, but the ones shot at f/8 tended to look better.

I still have a lot to fix on the computer right now and can't browse all the photos I took, but more than half were in sharp focus, and about half of the remainders were in OK focus (what I would have considered good before learning focus trap). The focus trap technique seems very reliable at getting the focus right, and I believe most shots that weren't in focus were due to my own actions (turning the focus ring too fast, camera movement), and occasionally because the bird was just moving too fast.

However, there were plenty of times where the technique failed to produce any photos even though a bird may come into focus at the center focus point. I think sometimes the AF may just be too picky. Getting that "instant shot" is not very likely using this technique, though I suppose if you're practiced, you could keep the focus on the subject a bit longer while continuous shooting and improve the odds.

As far as continuous shooting goes, the camera would only really shoot continuously if it detected good focus each time, so the odds of each shot being sharp were the same as when shooting single shot. The first shot I posted was 1 of 3 in a continuous sequence that all turned out sharp. I don't have the second one uploaded, but here's the third one:

I uploaded 16 photos from this shoot to Photobucket, but that was being really picky. There were plenty of shots that I didn't upload that before that day, would have been my best bird in flight capture yet. I didn't post all 16 because even though they all turned out well, it still gets boring to look at so many seagulls. Here's the gallery if you're interested though:


Thanks for looking! I look forward to seeing who else experiences the kind of results I got with this technique.
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Old Jun 10, 2007, 12:18 PM   #17
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You got some nice shots there Corpsy. I am actually as impressed with how well you metered for the white seagulls as how well you used the focus trap. I dont' try birds in flight that often but I have decided that the manual focus lenses actually work better than the auto focus. At least my Sigma loves to go through it's entire focus range every single time I push the shutter button and by then the shot is generally lost.

The focus trap can work well for macro shooting also, but, instead of having to adjust focus on the lens, you just hold the shutter button down as you sway in and out of perfect focus.

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Old Jun 12, 2007, 4:14 PM   #18
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Some really great pictures Corpsy.

This focus trap technique is amazing. I used it this weekend for taking portraits. People are alot happier when they have to wait less...

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