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04-14-2010, 09:19 AM   #1
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Focus and Exposure lock?

Bear with me, I hope I can type out what I am trying to ask.......

I always use center focus and center weighted metering. I focus on the eyes, use the skin tones to meter, recompose and shoot. So I recently read about and put my camera on "exposure and focus lock" so when I focus on a subject push the shutter button half down and then recompose, it locks both the focus and the exposure. Should I be doing it dif? using the shuuter button half down to lock focus and the AE-L button to lock exposure? since I usually only take pictures of people, I thought by locking the two together it kind of took away one step, so I just have to use the shutter botton half down to lock both.

So, I recently read that using center focus isn't the greatest way because the subject, especially kids, can move by the time you recompose and shoot. So I should be using the settign that lets me choose which part of the shot to focus on sicne then even if I recompose, if I choose the spot that is closest, i will be moving less and it will be quicker and giving the subject less chance of moving and giving me an image where I miss focus. SOOO....another question, if I change it to this way of focusing (Where I toggle my focus points) Will I also have to change the metering mode? or would I still use the center to meter, then toggle for focus and then recompose?

04-14-2010, 09:37 AM   #2
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I'm curious; have you noticed a problem with the sharpness of your photos or is this question based on your readings?

I'm unfamiliar with the metering modes of the K10D but you would not want to use center weighted metering if your subject is far from the center. Segment metering might give you a better shot at the correct exposure with off center subjects. While kids may run around, the light setting they're under typically won't change drastically unless they're running in and out of the shade. You may very well be better off not metering again after grabbing the correct exposure.

I would not dump focus and recompose just yet. Stopping down and using hyperfocal distance to your advantage will give you leeway and time to recompose. Focus and recompose has its own problems but I think it's probably not as bad as that article makes it seem. You can also let the camera auto-select the focus points if the kids are moving too fast. Fortunately, the k10d should have focal cues in the viewfinder, unlike the K-x.
04-14-2010, 09:40 AM   #3
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Okay, I'm still re reading and trying to make sure I understand...but one quick question by saying

QuoteQuote:
the light setting they're under typically won't change drastically unless they're running in and out of the shade
do you mean, that locking exposure may not be that important?

Oh, and haven't noticed a huge problem with focus with using center focus, locking, then re composing. I mean, I get some shots that are OOF, but I"m wondering if I will be able to nail it ever time (Or close to every time) if I do it a dif. way.
04-14-2010, 09:57 AM   #4
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Locking focus and recomposing is far faster than adding locking exposure to the step.
I only lock the exposure if there is a large difference on the shades of the subject..like one part is heavily shaded or shadowed.
If most of the subject is lighted fairly balanced, then I would say that locking focus and recomposing is all you need to do.
Now if you had spot instead of center weighted metering, then it would be more different since wherever the light where the spot falls on would be what the camera would adjust the meter for.

04-14-2010, 10:08 AM   #5
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QuoteOriginally posted by BethC Quote
do you mean, that locking exposure may not be that important?
No, it is not that important most of the time. Unless the lighting situation is constantly changing drastically, there's no reason to add an additional step of metering prior to each shot. If you must insist on metering before each shot, I would recommend metering first, then focusing to cut down on the time interval between focal confirmation and shutter depression. Incorrect metering is easy to fix in PP, focus issues are not.

QuoteOriginally posted by BethC Quote
Oh, and haven't noticed a huge problem with focus with using center focus, locking, then re composing. I mean, I get some shots that are OOF, but I"m wondering if I will be able to nail it ever time (Or close to every time) if I do it a dif. way.
Do you know why they are OOF? A lot of reasons can contribute to it and your solution only protects against one, which is an object moving during your recomposing stage. How long do you take to recompose? One solution is to slowly compose first, remember the composition, center focus, then recompose back. This adds more time between each shot but cuts down on the crucial moment between focus and shutter. The other option is my aforementioned method of stopping down to achieve a hyperfocus distance that the subject can freely move in and still achieve satisfactory sharpness, unfortunately this does not work well with lenses that have razor thin DOF.
04-14-2010, 12:02 PM   #6
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Shooting RAW, you have some latitude (wiggle room) with exposure. Pictures that look too bright or dark when chimped can be fixed in RAW development. For most general shooting, set AE and AF to matrix metering and focus. If your target scenes are too complex in terms of subject, THEN you use center-weighted, and meter and lock, and recompose and shoot. Spot-metering is tricky; if that spot isn't the equivalent of medium gray, the exposure can be way off.

On my K20D I can go into the Custom menu and set the Program Line priorities to default, or shutter or DOF priority, or best possible image (MTF). These settings affect the camera robot's brain when you're shooting in P(rogram) or Green mode with a modern lens. For moving subjects, pick shutter priority. For subjects at varying distances, pick DOF priority. For subjects that just sit there, pick MTF priority.

Here's what I do: For moving subjects, I'll use a fast shutter. If it's ME that's moving, and grabbing what's happening around me, I'll use a wide focal length and a stopped-down aperture for maximum DOF and minimum worries about focus. If the subject and I are stationary, I'll use a medium aperture and the fastest shutter possible. If there's lots of action, I'll use a fast shutter, wide enough aperture, and let the ISO float. And the focus and metering are center-weighted, so I just shoot what's centered and crop later.

Those are just general rules. Your mileage may vary.
04-14-2010, 03:05 PM   #7
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Okay, had to go away for a bit and thought a lot about this while driving

So this is what I came up with (I may be way off....someone set me straight if so)


this winter we had a rockin awesome blue sky. I was taking pictures of a chicadee in a tree but really wanted the sky to be what was exposed correctly, so in that case I metered off the sky, and I locked the exposure (using the button on the back of my camera that locks it...Not with the method I originally posted about, where it is locked along with focus with my shutter release button) then recomposed, focused on the bird and I really got (what I think) is an awesome shot, with a really beautiful sky. In that case, having the focus AND the exposure both set to lock when I push the shutter half down, would not have let me meter off the sky and then recompose and focus on the bird, it would have metered off and exposed for the bird, and I may not have gotten that awesome sky that I got in the shot. So if I were to take pictures of only chicadees, I would be better off UNlocking the focus and exposure so they are not both on the same button and just using the button on the back of the camera that locks exposure. Does that sound right?

But, when doing portraits, it really doesnt' matter as much since really you want to expose for the skin (MOSt times) and you usually focus on their eyes anyway, so really when you recompose, you don't really change the lighting you are exposing off of anyway, so really even using the exposure lock button that just locks exposure from one frame to the next is really a waste of time. I wonder if that's the same when shooting a group of people though?


QuoteQuote:
Do you know why they are OOF? A lot of reasons can contribute to it and your solution only protects against one, which is an object moving during your recomposing stage.
when thinking about this, as I stated before, I don't get an abnormally amount of photos where I miss focus, BUT....I think when I do, it's because of the subject moving slightly. For examply, I recently shot a Senior and didn't get one single shot where focus fell somewhere other than where I wanted it too. I think with an older person it's because you say "Stay" and they stay. As opposed to 6 month old twins I recently shot where I had some images where the focus fell somewhere other than where it was supposed too. Must be because in the amount of time it took me to recompose, he/she moved (and they moved a LOT...trust me) So really, I'm not unhappy with my focus most times, so maybe I shoudl just leave well enough alone?


RioRico I do shoot RAW, and I am thankful for that "Wiggle room" you mentioned. It has saved me that's for sure. I just really love the thought of nailing it in camera and having NO post processing work to do (haha sounds great right!? don't we all wish for that) I guess my questions are just because I wanted to know, again, I'm not disapointed in results I"m getting, I just want to know if there is a better way. So, I always shoot in manual and adjust my settings according to light and movement of subject...all that good stuff. and I always have my camera set too spot metering and center focus. I wonder how much different center weighted metering is. I think I may have to take baby girl out and mess around with them both some.

I'm also still confused about the back button focus button that so many people rave about. I'm still not sold. Of course, I've never tried it. Maybe if I did, I'd rave too. Can anyone tell me why back button focus is better than just pushing the shutter button half way down? May have to try that out later too. I may be back to post my rave!!
04-14-2010, 03:43 PM   #8
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Wow, that's a lot of stuff to get through and it covers several different topic areas. As far as focus goes, you have no problem, it seems, unless your subject moves. The only way around that is to take photos faster, so definitely locking exposure and all that is time wasted. I would also recommend just bumping the ISO to get a faster shutter speed. With fast children or pets you simply need to accept that more shots will be messed up.

QuoteOriginally posted by BethC Quote
I'm also still confused about the back button focus button that so many people rave about. I'm still not sold. Of course, I've never tried it.
Well, you should try it before buying or selling.

But generally it is suitable for cases where one can dial in the focus and then just leave it there. Like sports. You know the horses are coming around the track at exactly the same place. You get focus there using the back button because you do not want that changing until you decide again to do so. Decoupling focus from the shutter button helps prevent errant focusing that would actually work against you.

04-15-2010, 01:37 PM   #9
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Or a setting where the subject isn't moving, but is partially obscured, like a bird in a tree. If you manage to get the focus right with AF for one shot, you certainly don't want the camera continuing to refocus between shots and risk getting it wrong next time. You could switch to MF mode to do this, but using the button for focus is often more convenient way. The idea is, *you* want to be in control of when the camera focuses and have an easy way of taking pictures *without* refocus when you want. I accomplish by assigning my back button to temporarily *cancel* AF.

As for your exposure question, to me, worrying about stuff like that is one reaosn I shoot in M mode exclusively. Exposure is locked when and where I tell it to be, period.
04-15-2010, 03:34 PM   #10
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Marc, I shoot in only manual as well. So I guess it's something I don't have to worry about then?
04-15-2010, 03:39 PM   #11
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QuoteOriginally posted by BethC Quote
Marc, I shoot in only manual as well. So I guess it's something I don't have to worry about then?
Exactly. Your camera is not trying to second-guess you in M mode. It keeps both the aperture and shutter speed exactly where you dialled it in (ISO too). So what is there for Aperture Lock to do? Nothing.

I would say, though, that in those cases where you have a child moving around quickly, maybe you should try more automation. Let the camera adjust focus point, aperture etc. and see if you don't get more shots. It is worth a try.
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