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05-20-2016, 12:16 PM - 1 Like   #1
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K-1 Larger Center Focus Point Than K-3?

So, I've been taking quite a few photos of my daughter with the K-1 and am really liking it! However, I'm wondering if the Central Focus Point is larger than on most other bodies? I know in the viewfinder shows it as quite a bit larger; I also know that the size of square it shows wouldn't necessarily reflect the actual size of the focus point.

When using the DA 40 Limited, or other f/2.8 lenses, I can point and focus at the eye in the eye-socket and have a photo with the eyes being nicely in-focus and sharp. However, when using the FA 77mm wide open or less than f/2.8 I am getting consistent focus on the tip of her nose (or eyebrow area) instead of on the eye; thus the wondering if a bigger focus point area might be focusing more on the external eye-socket area instead of being small enough to jump in at the eye.

I understand that the focus points are rated at f/2.8, so missed should be expected at f/1.8, but they just seem too consistently towards the front.

That brings me to AF micro-adjustments. I'm researching different methods on how to do that without too much more gear/equipment, though I am open to getting a proper setup. I set a yardstick up at a 45deg angle (bottom of stick on floor, closest to camera; top of stick against wall) and focused on "20in". Taking several handheld shots, they all showed that the closer 19in mark was more in focus than the 20in mark, as was the 18in more in focus than the 21in mark. Looked like obvious front-focusing, and I was excited. Then I put it on the tripod to confirm my suspicions, and after focusing and taking shots multiple times it looks to be back-focusing more than front-focusing. Perhaps the fault is all in the photographer, and I consistently back up slightly while taking a photo? I can't imagine that being the case so consistently, but I'm definitely quite curious about where the issue is stemming from!

Thanks for any suggestions or ideas!

05-20-2016, 12:24 PM   #2
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The viewfinder has two AF point indicators for each point- a larger one to indicate in-focus, and a smaller one inside it to indicate the active AF points when in A-9 or SEL-3 mode. I don't think the points themselves are any different than before.

QuoteOriginally posted by aikilink Quote
That brings me to AF micro-adjustments. I'm researching different methods on how to do that without too much more gear/equipment, though I am open to getting a proper setup. I set a yardstick up at a 45deg angle (bottom of stick on floor, closest to camera; top of stick against wall) and focused on "20in". Taking several handheld shots, they all showed that the closer 19in mark was more in focus than the 20in mark, as was the 18in more in focus than the 21in mark. Looked like obvious front-focusing, and I was excited. Then I put it on the tripod to confirm my suspicions, and after focusing and taking shots multiple times it looks to be back-focusing more than front-focusing. Perhaps the fault is all in the photographer, and I consistently back up slightly while taking a photo? I can't imagine that being the case so consistently, but I'm definitely quite curious about where the issue is stemming from!
Hand-held testing isn't going to get you anywhere, but the yardstick approach should. Make sure there is a clear focusing target where you're focusing the camera, such that it does not focus on something other than what you expect. Also, be sure that the yard stick is angled at exactly 45 degrees, and ensure that the camera is vertically level (the in-camera level should help there) and horizontally aligned with the stick.

A lens alignment tool would of course make life easier

Fixing Front and Back Focus - LensAlign MkII - In-Depth Articles

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05-20-2016, 12:38 PM   #3
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QuoteOriginally posted by aikilink Quote
That brings me to AF micro-adjustments. I'm researching different methods on how to do that without too much more gear/equipment, though I am open to getting a proper setup. Thanks for any suggestions or ideas!
I have a favorite flowering plant I use. Since it grows in clusters of flowers, stems and leaves, I can focus on a specific flower, and based on which actual flower or leaf or stems is in focus, I can figure out if a lens is front or back focusing

I got very frustrated with lens align because it's somewhat finicky about the whole camera level, 45 deg angle requirement. I don't have anything in my house that I could rest it on at a comfortable height for ME to fiddle with LV, PDAF, Menus etc for 20-30 minutes. It also requires very good lighting, beyond what I normally have in the house.

My backyard plant has numerous clusters that let me set my tripod at a comfortable height for me and Phoenix sunlight is plenty bright enough.
05-20-2016, 01:16 PM   #4
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QuoteOriginally posted by aikilink Quote
So, I've been taking quite a few photos of my daughter with the K-1 and am really liking it! However, I'm wondering if the Central Focus Point is larger than on most other bodies? I know in the viewfinder shows it as quite a bit larger; I also know that the size of square it shows wouldn't necessarily reflect the actual size of the focus point.

When using the DA 40 Limited, or other f/2.8 lenses, I can point and focus at the eye in the eye-socket and have a photo with the eyes being nicely in-focus and sharp. However, when using the FA 77mm wide open or less than f/2.8 I am getting consistent focus on the tip of her nose (or eyebrow area) instead of on the eye; thus the wondering if a bigger focus point area might be focusing more on the external eye-socket area instead of being small enough to jump in at the eye.

I understand that the focus points are rated at f/2.8, so missed should be expected at f/1.8, but they just seem too consistently towards the front.

That brings me to AF micro-adjustments. I'm researching different methods on how to do that without too much more gear/equipment, though I am open to getting a proper setup. I set a yardstick up at a 45deg angle (bottom of stick on floor, closest to camera; top of stick against wall) and focused on "20in". Taking several handheld shots, they all showed that the closer 19in mark was more in focus than the 20in mark, as was the 18in more in focus than the 21in mark. Looked like obvious front-focusing, and I was excited. Then I put it on the tripod to confirm my suspicions, and after focusing and taking shots multiple times it looks to be back-focusing more than front-focusing. Perhaps the fault is all in the photographer, and I consistently back up slightly while taking a photo? I can't imagine that being the case so consistently, but I'm definitely quite curious about where the issue is stemming from!

Thanks for any suggestions or ideas!
If you want to know the real size of the center point do this:
put your camera on af-c. pick a target that is flat and stands out from the background (like a square pole that is 20 feet in front of the background) now focus on the background. with your shutter button half pushed, pan the camera slowly until the pole is in focus. you will notice it won't be exactly where your center point is. now do this the opposite way, then up then down. make a mental note what the actual size of the center point is. it might surprise you!
hope this makes sense

05-20-2016, 02:37 PM   #5
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QuoteOriginally posted by nomadkng Quote
I got very frustrated with lens align because it's somewhat finicky about the whole camera level, 45 deg angle requirement. I don't have anything in my house that I could rest it on at a comfortable height for ME to fiddle with LV, PDAF, Menus etc for 20-30 minutes. It also requires very good lighting, beyond what I normally have in the house.
If you don't have a spare tripod or lightstand for it, it might be handy to know that the standard household table lamp works fine. take the lampshade off, screw the lensalign onto the screw, which is the same screw thread as a tripod - and you're good to go. The downside of doing it that way is it means you can only level it with your camera (it's a lot easier if you have a ball head on both sides - you rough in with the camera adjustments, then pinpoint adjust it so looking through the tiny hole in the back shows the center of the lens). But even if you're off a bit on that, it's still a lot more accurate measurement than handholding and pointing it at flowers will be.

And I don't know what you mean about lighting requirements. It just requires even lighting on the target. Simply making sure there's a lamp somewhere above & between it and the camera and nothing casting shadows on it suffices. It doesn't have to be super bright - you're on a tripod, using a remote, and probably with the mirror locked up - nothing is stopping you from extending the exposure to compensate for using a 60 watt bulb instead of a 100 or something.
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