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07-28-2014, 03:44 PM   #1
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Autofocus issues

So I've got two separate autofocus problems and am looking for some help finding a solution.
First, In Low light, the af hunts and hunts and never focuses. Im aware it's because of the lack of light but what can I do to fix it? Manual focusing is not a viable solution since the focus confirmation light doesn't come on. I'm assuming it uses the same sensor as the af. Even when my subject is backlit, like a person in a crowd at a concert, it still has trouble locking on. When it does, it's not the point I wanted to focus on.
Which leads me to my next problem.
Probably about 30-40% of the time, my pictures are not focused on what I was intending to focus on. Even in daylight. When I look at my pictures on the computer, something completely different is in focus. For example I took pictures of my wife on a bench, had the center point on her eye, everything seemed like it focused fine but when I got home, her pants were in focus and not her face. I have the af set to center point and not auto. I have a k50 btw.
Thanks for any input.

07-28-2014, 03:59 PM   #2
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1. as you feel it is becoming harder and harder to focus, you can use wider focals. Using wider focals you can take advantage of the larger depth of field. Look for something that is bright and at about the same distance from you, as the subject you want to photograph.

AF will require longer time to lock, if it can lock at all, when light level is low. Even small camera or subject movements can make it harder - wider focals can make this easier, but it's not a guarantee. This is when I attach my flash to the camera, stop down to something like f4 or f5.6 and switch to manual focus. I don't walk around manually focusing all the time. I preset the focus to maybe 1-2 meters away, and the smaller aperture will to a higher degree make sure I'll get good sharpness, as long as I don't change my distance to subject too much.

This last trick has allowed me to take tons of photos and do it super fast, for instance while people are dancing i super low light. Give it a shot.

2. I can't say anything for sure about this one. You might need to provide with some sample photos along with EXIF inormation. Perhaps you are experiencing a front focus issue, but it's too early to claim that. When you focus, do try to focus more than once. Sometimes I force the camera to change the focus distance drastically by for instance pointing it towards the ground and focus. In my experience, sometimes the camera can have focus close by but not exactly where it needs to be, and even a re-focus isn't always enough to make it understand it needs to be closer. You might very will be out in daylight, but if you are shooting on the shadow side, the details actually might be too vague for the camera to pick up. shooting against strong light can have an affect also.
07-28-2014, 04:37 PM   #3
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QuoteOriginally posted by Another dyemention Quote
So I've got two separate autofocus problems and am looking for some help finding a solution.
First, In Low light, the af hunts and hunts and never focuses. Im aware it's because of the lack of light but what can I do to fix it? Manual focusing is not a viable solution since the focus confirmation light doesn't come on. I'm assuming it uses the same sensor as the af. Even when my subject is backlit, like a person in a crowd at a concert, it still has trouble locking on. When it does, it's not the point I wanted to focus on.
Which leads me to my next problem.
Probably about 30-40% of the time, my pictures are not focused on what I was intending to focus on. Even in daylight. When I look at my pictures on the computer, something completely different is in focus. For example I took pictures of my wife on a bench, had the center point on her eye, everything seemed like it focused fine but when I got home, her pants were in focus and not her face. I have the af set to center point and not auto. I have a k50 btw.
Thanks for any input.
On your first question, what is the lens you are using and what are your settings; ISO, aperture, shutter speed? and Are you shooting in A, M, Tv, TAv? Do you have the AF Assist light activated (in the REC Mode menu)? Are you using AF.S or AF.C? The K-50 has very good AF but they all have to have some light and contrast. If you are using a tripod it's a simple solution, go to manual focus and live view. Focus peaking is exceptional in low light shooting, but you need to be on a tripod.

On you second question, first make sure you aren't using AF.C, the slightest movement can change the focus. If in AF.S make sure you aren't in release priority, it's made for continuous hi speed shooting and can fire before focus is achieved. Get your settings and technique down before you get into lens adjustments. I think it would be a real stretch for your lens to be that far out of focus, that would be a serious defect.
07-28-2014, 05:16 PM   #4
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I primarily use a DA 50 1.8, especially in low light. Of concerts I usually have my shutter at 100 and my ISO at 800-6400 depending on the lighting. I do speed up the shutter if the performers are moving a lot btw. I always shoot in manual unless I'm taking pictures of my kid. He's two years old and it's way too hard to switch the setting while he's running around. I just checked and I am in focus priority btw.
As far as the first reply, I can't really use much slower aperture since the lighting is low in the first place. I'll try it next time though. And I'll post a picture when I get back home by my computer.
Thanks for the help so far.

---------- Post added 07-28-14 at 05:22 PM ----------

Oh and the focus assist light doesn't help much since I'm usually just past it's range. I am usually taking shots of people dancing in the crowd and could probably benefit from a 35mm so I can get a bit closer but my 50mm is my best bet. I do have a Tammy 28-105 4-5.6 but it's slow, not sharp, and hunts I bright light.

07-28-2014, 05:51 PM   #5
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When photographing moving subject under difficult circumstances, I find that release priority can help.

As for the smaller aperture, it was meant to go along with a flash - if you can use a flash in the first place.
07-28-2014, 06:50 PM   #6
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That's why I switched to the AF button (on K5,K5IIs). I still find it works better than the "half press" job which causes it to refocus every time you press the thing... and one will press it without knowing too and the focus will be off. I found that it works better in low light as well. I only switch to the shutter release when I'm working on moving things because the AF button can be a hindrance or even a pain to operate quickly.
PS: that's one thing the K3 has (finally) ... a well placed AF button.
07-28-2014, 06:53 PM   #7
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I use the back AF button as well. I changed because I wanted to know what the fuss was about. I didn't like it at first tbh, but after a portrait session or two, I realized why it's so great. Now I use it all the time.
07-28-2014, 07:09 PM   #8
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So this is one example of my camera not focusing correctly. I obviously intended to focus on her face and not the head of the guitar but her face is out of focus and the guitar head is in focus. Its clearly the object with the highest contrast so I can understand it would focus on that if I were using auto 5 or auto 11. But as I said, I use center point so I don't have any idea why it would disregard where I was "aiming" and focus on something else.

---------- Post added 07-28-14 at 07:28 PM ----------




Last edited by Another dyemention; 08-05-2017 at 12:47 PM.
07-28-2014, 07:34 PM   #9
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And as you can see in this photo, the focusing came out good. I even took this handheld at 1/50 second. And the only light was a 16' LED strip on the ground.


Not sure why this has a slight over saturated look when I posted it. It looks great in lightroom. Oh well, im new to this and you get the idea.

---------- Post added 07-28-14 at 07:42 PM ----------

And this picture also looks perfect on Facebook. Not sure why it looks so crappy on here. Any ideas? Not to hijack my own thread.

Last edited by Another dyemention; 08-05-2017 at 12:47 PM.
07-28-2014, 07:55 PM   #10
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Make sure the focus is locked in before taking a photo. I get the feeling there is more movement going on, on the first photo which could indicate the camera would need more time to lock and I do not suppose she moved that bit back before you took the photo. On such cases (movement and low light) I tend to switch to continuous focus using release priority - I don't always do that, but I especially do it if I have to recompose as well. It's still hard to say for certain what the cause could be. For now I'm thinking your technique might be off, but I could easily be wrong.

You could do some test shots using static subjects, such as a brick wall. See how that goes.

The oversaturated look on the second photo is because the photo was saved in sRGB colorspace (which is should be). But it's a smaller colorspace than what Lightroom uses, and that tends to give such a look.

---------- Post added 29-07-14 at 05:11 ----------

Not sure why it looks fine on Facebook but not here - possibly a stronger compression on this forum?
07-29-2014, 02:56 AM   #11
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I'll try doing some tests as you suggested. I suppose it's possible that I am the problem. Maybe I'm not steady enough. Since most of my shots are 1.8, any slight movement would throw it off.
So how do I fix the problem with my posted photos? Like I said, it's perfect in LR as well as Facebook. The color is even slightly off on here. And when I look at this post on my iPhone, it doesn't even look to be in focus.
Thanks for all your help. Appreciate it
07-29-2014, 03:29 AM   #12
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Your issues are similar to what I used to encounter when learning how to use wide aperture lenses. The fix for me was, and still is: -

1) Install a split prism focussing screen so you can see exactly what the lens is focussing on in either AF or manual mode. The AF sensor metering segment is too large and you won't be able to control the point it selects to discriminate between, say an eye or an ear or an eye brow. This makes a huge difference with narrow DoF. Not sure about your camera, but the K20D also has trouble in tungsten light just to add to the problem.
2) Manually focus in low light. I have a 50mm F1.4 and a 77ltd and never use AF below F3.5 - it's too unreliable. If I don't have a solid edge to focus one, I pick a spot with a nice vertical edge on the same plane as my target focus point and then take a couple of shots deliberately tweaking the focus ring forwards and backwards (like a manual focus bracket.)

The split prism screen also helped me resolve a front focussing issue I had too. If you can't afford a split screen, try my second suggestion and see how you go.

You'd be surprised how little practice you need to outperform your AF.
07-29-2014, 03:21 PM   #13
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Another dyemention: if the problem regarding the second photo is compression related, which I believe it is, then you can't do much about it. You can try and make a Pentax copy, with lower saturation, so the compression algorithm doesn't have to crunch is as hard - this route can be a bit trivial in the long run.

Can you post a link to your Facebook version? then it's easier to understand how much it is off here.
07-29-2014, 05:29 PM   #14
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https://m.facebook.com/steve.zavodaiii/albums/10203217666699713/?notif_t=like
This is a link to the album. It's actually my first attempt at doing photography work for someone. Feel free to critique btw. I'm open to suggestions.

---------- Post added 07-29-14 at 05:31 PM ----------

And jawsy, I've been eyeing the katzeye for a bit now. I was actually waiting to see if someone would suggest it. Just got my car paid off so should add it to my kit soon.
07-29-2014, 06:15 PM   #15
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Thanks for the link. I'd say colors are the same, but the compression is much more aggressive on the photo from Pentaxforum. Looking at the filesizes, the PF photo is 58KB while the Facebook photo is 92KB. The Facebook photo is slightly larger, but that shouldn't make up for the extra filesize.

My conclusion is: more compression is used on PF. If you have a site, then upload there and embed photos to PF posts.
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