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08-07-2009, 06:00 AM   #16
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QuoteOriginally posted by deludel Quote
Will, I just gave it a try. My thumb needs to get used to going for that AF button (and not the +/- button) but other than that, I can see how this will be a great tool for me! That 1/2 press AF technique was causing more harm than good, I suspect.
Oh, I dunno. Whatever works for you. I think using the AF button works better for me, though.


QuoteQuote:
A couple of follow-up questions regarding Custom Menu Settings. What are your settings/input on the following:

- AF Button Function:

(1) Enable AF ... this is where I have it set now
(2) Cancel AF ... this has something to do w/ the shutter button, but I am not sure what
(3) Center of AF Point .. I think it auto-sets AF point at center when the dial is on "SEL"
1 - Enable AF

QuoteQuote:

- AF but Press Halfway

...thanks to you, I shut this to 2/Off
Right.


QuoteQuote:

- AE-L with AF locked

.. I have this set to "off", I dont think I want AE locked like this (I use the AE-L button when I need to)
Right, that's what I do, too.


QuoteQuote:
- Link AF Point and AE
.. Again, I have this turned "off". I feel like this is almost the same as spot-metering,which I would rather consciously turn on when I want to
Right again.

It takes just a little practice to get used to it.
Will

08-07-2009, 11:24 AM   #17
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Slightly on-topic:

From what I gather from memory, the only lenses that can be called zooms are parfocal lenses. Verifocal lenses aren't zooms, they're...varifocal lenses. At some point all lenses that were not primes became known as "zoom" lenses, and here the problems started.

I believe Vivitar were one of the first to popularise the varifocal design, which allowed them to make smaller, faster lenses, and simplified R&D.

Further, I'd bet that most consumer zooms are varifocal, and most (professional) constant aperture zooms are parfocal. The two DA kit lenses are certainly varifocal.

I owned an old Tokina 35-70mm f/2.8 and in the instructions they specified that it was "a true zoom" (meaning parfocal) and explained that to achieve the sharpest images at 35mm one should zoom to 70mm, focus, then zoom out to 35mm.

I used to think that varifocal lenses were always variable aperture, but I own a Tamron 17-35mm f/2.8-4 that behaves like a parfocal lens. To achieve the sharpest images at 17mm I need to zoom in to 35mm, focus, then zoom out to 17mm and take the shot. I've read somewhere that some of Canon's older lenses where parfocal despite being variable aperture.

.
08-07-2009, 12:34 PM   #18
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QuoteOriginally posted by Miserere Quote
Slightly on-topic:

From what I gather from memory, the only lenses that can be called zooms are parfocal lenses. Verifocal lenses aren't zooms, they're...varifocal lenses. At some point all lenses that were not primes became known as "zoom" lenses, and here the problems started.
Yes, that's in line with what I have now read elsewhere - except that would not say "the only lenses that can [present tense] be called zooms..." That might have been the case once but it certainly isn't now. And to be honest this makes practical sense ("varifocal lens" is a pain to say) and logical sense (zooms are called zooms because they zoom, i.e. change focal lengths, NOT because they maintain focus when they do so).


QuoteQuote:
Further, I'd bet that most consumer zooms are varifocal, and most (professional) constant aperture zooms are parfocal. The two DA kit lenses are certainly varifocal.
But now I'm back almost where I started. I can't find much in the way of firm info on this. Instead I find lots of statements like "I bet that consumer zooms are varifocal" or "the Pentax 18-250 is almost certainly (or probably) parfocal...."

I have come to the (tentative) conclusion the the parfocal/varifocal distinction is NOT a hard and fast one. It doesn't, for example, seem to be based on some precise differences in the manner of construction, because if that were the case, I'd think that lens makers would tout their parfocal lenses, but I can't find a single lens that identifies whether it's one or the other type. It seems to me that parfocal and varifocal are just terms used to describe a user's experience with a particular lens. If it maintains good focus when you change the focal lengths, it's parfocal, otherwise not. Am I wrong?


QuoteQuote:
I owned an old Tokina 35-70mm f/2.8 and in the instructions they specified that it was "a true zoom" (meaning parfocal) and explained that to achieve the sharpest images at 35mm one should zoom to 70mm, focus, then zoom out to 35mm.
Maybe the old lens makers made an issue of this. I just can't find much info about it recently at all.

Still wondering: Is the Pentax 18-250 parfocal or not? Don't want an opinion - I want sure or authoritative knowledge.

Will
08-07-2009, 01:24 PM   #19
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QuoteOriginally posted by WMBP Quote
Lori,

Give it a try, you might like it.

I shoot weddings and other similar events (Catholic Confirmations and First Communions, etc.) and often have to shoot in low light. Using AF to focus means that I can focus once, and if I don't move, I don't have to keep focusing. And this helps a lot because in low light the camera sometimes has trouble locking focus. I started using the AF button last year after missing a number of shots at a First Communion due to the camera's autofocus kicking in unnecessarily and getting confused. It might lock focus quickly on a girl wearing a white dress with flowers on the front, but when a boy with a dark suit stepped to the same spot the camera wasn't sure where the focus was.

Using AF button to focus has other advantages most of which comes simply from the fact that I now focus more deliberately, more purposefully. Out of focus shots were never a huge problem but I am sure I get even fewer now than I used to.

The ONLY drawback is when I lend the camera to a stranger who has kindly volunteered to take a photo of my wife and me, say, while we're hiking or something. Everybody expects focus on half press, and I have to quickly explain, no, press AF to focus, then press the shutter to take the photo.

Will
I've been playing with this lately, and I've run into a few (personal) issues with this approach:

- Shutter is fired at all times, even without locking focus. After focus has been locked and before pressing the shutter, I often forget to remove my thumb off of the AF button, which results in mis-focused pics as the camera/lens keeps on its focusing routine.

- It's hard to get to the AF button if one is left-eyed.

- Battery grip doesn't have its own AF button. It is practically impossible to reach the AF button on the camera body with the grip on when in vertical position.

Wasim

08-07-2009, 02:22 PM   #20
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QuoteOriginally posted by wasim_altaf Quote
I've been playing with this lately, and I've run into a few (personal) issues with this approach:

- Shutter is fired at all times, even without locking focus. After focus has been locked and before pressing the shutter, I often forget to remove my thumb off of the AF button, which results in mis-focused pics as the camera/lens keeps on its focusing routine.
Um, try to remember to stop pressing the AF button before shooting? :-)

This isn't a problem for me. I do generally keep my thumb on or near the AF button, but I only press it when I want to autofocus. I have never had the problem you describe.



QuoteQuote:
- It's hard to get to the AF button if one is left-eyed.

Hmmm. By "left eyed," I assume you mean that you put your left eye to the viewfinder. I do that myself. And I should perhaps add that in addition, I have both a big nose and big hands and fingers. Still, I manage to get my thumb in there somehow. I don't think about this much so I just did a little test: picked up the camera and looked through the finder as if I were going to shoot. My nose was touching my thumb. For some reason it just doesn't bother me.

You do raise a question in my mind, though. I wonder if this would be MORE of a problem if I were shooting with the smaller K-7 instead of the K20D? Dunno. I haven't had a chance to hold a K-7 yet.


QuoteQuote:
- Battery grip doesn't have its own AF button. It is practically impossible to reach the AF button on the camera body with the grip on when in vertical position.
OK, THIS complaint is one I can share. My solution is simple: I've stopped using the shutter button on the grip when I shoot in portrait orientation. I simply keep my hand on the (normal orientation) right side of the camera all the time. Don't like this but it works okay.

Will
08-07-2009, 03:06 PM   #21
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This was the type of focusing I was used to when I was using film cameras, but when I tried it with the DSLR now, it didn't seem to work that's why I quit doing it.
Zooming in and focusing was great to get tack sharp focus and I never failed to get tack focus each time during the days.
I was actually kinda frustrated that the lenses that I have now don't behave like the old zoom lenses.
I'm glad that I found out the explanation for this (parifocal and varifocal lens).
I guess I just have to try out all my lenses and see which behaves like what (varifoval or parifocal).
I hope I still have lenses like the old zooms as I was used to this type of focusing before and would still love to do it!
08-08-2009, 10:25 AM   #22
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QuoteOriginally posted by WMBP Quote
Um, try to remember to stop pressing the AF button before shooting? :-)

This isn't a problem for me. I do generally keep my thumb on or near the AF button, but I only press it when I want to autofocus. I have never had the problem you describe.

Hmmm. By "left eyed," I assume you mean that you put your left eye to the viewfinder. I do that myself. And I should perhaps add that in addition, I have both a big nose and big hands and fingers. Still, I manage to get my thumb in there somehow. I don't think about this much so I just did a little test: picked up the camera and looked through the finder as if I were going to shoot. My nose was touching my thumb. For some reason it just doesn't bother me.

You do raise a question in my mind, though. I wonder if this would be MORE of a problem if I were shooting with the smaller K-7 instead of the K20D? Dunno. I haven't had a chance to hold a K-7 yet.

OK, THIS complaint is one I can share. My solution is simple: I've stopped using the shutter button on the grip when I shoot in portrait orientation. I simply keep my hand on the (normal orientation) right side of the camera all the time. Don't like this but it works okay.

Will
Funny you mentioned the nose issue. Using my left eye actually keeps my long nose away from the camera and gives me better access to the view-finder. I can reach the EXP-COMP button easily, but need to have my thumb brush up against my nose to get to the AF button. It's just a matter of getting used to it, that's all.
I've ordered the Pentax magnifying eyepiece, which will hopefully give me some nose room (it's currently back ordered at Adorama).

One big advantage of using the AF button in this manner is the ability to manual focus with DA lenses that have quick-touch/shift manual focus -- there is no need to keeps the shutter half-pressed while focusing manually.

How do I find continuous AF with this method or tracking and quick-firing shutter in succession to catch fast moving objects?

Wasim
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