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01-26-2010, 08:06 AM   #1
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Inconsistent Focusing

Looking for some help with my focusing technique or lack there of. I'll use these photos for examples but this is a pretty common problem for me. I'm very inconsistent and don't know why.
In this photo I was trying to get focus on the girl in the middle. Instead, I got the background. But I took the second photo the same exact way and she came out in focus.

The pics were taken with either my 50 f 1.4 or my 28 f/2.8. both of which are manual focus lenses.



Same thing below. I was focusing on the head....and I got the backgorund. But...not doing anything different...the second time around the head was in focus. What gives?



Is this a case of focus and recompose? if so, can some explain how I should do that using these examples, like step by step directions. I'm confused about that techinique in general.
Thanks
Kevin

01-26-2010, 09:04 AM   #2
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i'm not understanding your problem

if your lens is a manual focus lens, what you see in the view finder is whats in focus

focus and recompose is for when you want something in focus that is not in the center..

are your hands shaky? mabybe your fingers move between shots and spin the barrel.

are you using the focus confirmation indicators?
01-26-2010, 09:27 AM   #3
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QuoteOriginally posted by Gooshin Quote
are you using the focus confirmation indicators?
yes, i'm using the focus confirmation. but i've read that it is generally just a guide.
01-26-2010, 09:41 AM   #4
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YMMV but manually focussing on APS-C is a farking nightmare.

I flat out cannot do it.

01-26-2010, 11:14 AM   #5
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There was an article somewhere (I think a post on this forum).

The focusing software has a certain 'play'. If you turn the focus ring coming from minimum distance, the focus indicator might indicate focus at e.g. 2 meter. If you do the same exercise coming from infinity, it might indicate focus at 2.2 meter. Furthermore, turning the focus ring slightly further will still cause the focus indicator to indicate that the subject is in focus so the question is what is true and what is not. If I remember the article correctly, the exact focusing method to use depends on the lens; practice and you will learn.

I have not played with manual focusing on a dSLR myself (the day will come soon), so can not speak from experience. But I expect that I will dearly miss a split prism.

WimS
01-26-2010, 11:21 AM   #6
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Mastering manual focus on Pentax DSLRs robertsdonovan.com ; found via the article section on lenses on pentaxforums
01-26-2010, 11:25 AM   #7
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QuoteOriginally posted by Deiberson Quote
yes, i'm using the focus confirmation. but i've read that it is generally just a guide.
what do your EYES tell you?
01-26-2010, 11:28 AM   #8
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QuoteOriginally posted by Alfisti Quote
YMMV but manually focussing on APS-C is a farking nightmare.

I flat out cannot do it.
I'm very glad that you said that, I've had a devil of a time with the K-7 having not used APS-C before. The split prism screen I purchased afterwards has helped, but somehow I still don't find it as easy as back in the good old days and still get more duffers than I ever used to!


Last edited by Nass; 01-26-2010 at 11:42 AM.
01-26-2010, 11:37 AM   #9
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when using lenses faster than about f/3.5 the focus screen is too slow to show accurate focus. ref: Manual Focus with AF DSLRs
01-26-2010, 11:45 AM   #10
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QuoteOriginally posted by Gooshin Quote
what do your EYES tell you?
that i'm in focus, the same thing that these articles are saying.
01-26-2010, 11:47 AM   #11
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QuoteOriginally posted by Deiberson Quote
that i'm in focus, the same thing that these articles are saying.
well you're doing something that you are not telling us

you cant take two identical photos and have one come out in focus and one out of focus, because you are clearly adjusting focus between the two shots.
01-26-2010, 11:50 AM   #12
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QuoteOriginally posted by rhodopsin Quote
when using lenses faster than about f/3.5 the focus screen is too slow to show accurate focus. ref: Manual Focus with AF DSLRs
Really, how am I managing to focus then?
01-26-2010, 11:52 AM   #13
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Delberson, have you checked your diopter adjustment?

What results do you get with a tripod? It could be that you slightly changing position without realising it.
01-26-2010, 12:00 PM   #14
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Kevin,


Couple of questions. Forgive me if you've already answered these. I looked but didn't see this info.

1. What focusing mode are you using on your camera - center spot, user-controlled spot, or auto? I'd recommend sticking to center spot focusing in most situations.

2. Do you frequently focus and recompose? How close to the subject are you when you do this? Distance to the subject matters because depth of field is shallower, the closer you are to the focal plane. So where focus and recompose causes problems is when you're pretty close to the focal plane - and it's worse of course if you're using a wide-open aperture like f/2.8 or something.

3. Do you have shake reduction enabled on your camera? The problems in your photos don't look to me like they're due to camera shake, but I thought I'd ask. I would suggest enabling shake reduction, and then keep the shutter speed reasonably fast.

4. Is it possible that you're simply standing too close to your subjects?

5. What lens are you using?

Will
01-26-2010, 12:19 PM   #15
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Response to Will,
focus mode....
user controlled but for these shots it was set to center.

distance was close and shots were probably close to open. i think this is the biggest contributor.

shake reduction enabled

the lens is the smc A 50mm f/1.4

DB,
i did not check my diopter adjustment. i'm still new to this and don't really know what that is. i was not using a tripod. its on my "i better get one of those f'n things real soon" list.

Gooshin,
i'm adjusting the focus between the 2 shots but i was focusing on the head(s) for all 4 shots. four times i heard and saw the focus confrimation from the camera with the head in the center. this is where my inquiry stems from. 50% of the time, i get the wrong object in focus when what i have showing in the center of the viewfinder is telling me i'm in focus. my nebulous skepticism comes from these inconsistent results.

based on these responses, i guess i'm probably just moving. i'll have to get a tripod see what happens.
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