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01-11-2012, 03:19 PM   #1
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Inexperienced user - got frontfocusing questions

Hello!

Inspired by my girlfriends wonderful pictures, I bought my first 'real' camera, the K-5 + 18-55 and 50-200 at a very good price in november. I've also bought 3 M-lenses off of EvilBay; the 28mm 2.8(the one i find myself using the most for...everything!), the 50mm 1.7 and the 100mm macro f4.
I've taken around 2000 pictures since november, most of which aren't very good in any possible sense of the word, but some i like. I've done a fair bit of reading about this and that, and after a while i started wondering why, especially with the manual lenses, it seemed like actually catching stuff in focus was completely random. A lot of this i put down to inexperience, but after buying a tripod and experimenting, i felt something was wrong. So i started reading, and stumbled upon FF/BF-issues, and today i've downloaded some charts, and done a few tests. And this is what prompted me to post a few questions here, which i hope someone will be kindhearted enough to answer.

-ALL my manual lenses frontfocused. I didn't know which way to turn the dial at first, so i put it at +5 to begin with. That didn't really change anything, so i decided to go to the other extreme, and dialed in -10. BANG! The 100mm macro was spot on! The 28mm was almost there, while the 50mm should probably be having a -12 adjustment. I accidentally dropped this on the floor the other day, perhaps that's got something to do with it. In any case, the question is, now all my manual lenses are either there, or thereabouts, but i'd like the 28mm and the 50mm to be spot on like the 100mm. Can this be another of my countless user-errors? Should i bother sending in the lot and have it professionally adjusted, since it's not THAT much, but just a little?

-Next came the AF-lenses. The 18-55 looked good! But hang on! Didn't i set it to 'apply to all' and -10? Yes i did! I found that a little weird, but then remembered reading something about newer lenses with their very own ID-chip gets remembered by the camera, and the 'apply to all'-setting wasn't in effect on these lenses. Next came the 50-200mm. A bit of frontfocusing here, so still with 'apply to all' and -10, i set 'apply to one' to -2. Right smack bang in the middle, and i'm happy as Larry. Almost. Because, if the apply to all and apply to one is cumulative, then it means ALL my lenses are off by between -10 and -12. Could this again be a user error? Or can it actually be my camera that needs a professional adjustment, somehow, somewhere?

I will do some more testing and experimenting on this, but this is how it looks now.

thanks,

M

01-11-2012, 03:27 PM   #2
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Manual lenses don't truly have front/back focus issues, as AF confirmation is approximate and there's no AF motor to bring the lens's focus to the middle of the range.

As far as testing your lenses go, you should try using the technique described here: Fixing Front and Back Focus - Introduction - PentaxForums.com

If all your AF lenses are off by that much, chances are it's your camera's fault.

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01-11-2012, 04:22 PM   #3
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Ah, thanks

When i think about it, a bit harder than whats good for me i suppose, i see what you're saying about MF-lenses not really having FF/BF-issues. Maybe i'm just too concerned about that red square, and doesn't pay enough attention to whats in the viewfinder. I will try to turn of the square and see if that helps me in any way
01-11-2012, 04:35 PM   #4
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QuoteOriginally posted by morpho Quote
Ah, thanks

When i think about it, a bit harder than whats good for me i suppose, i see what you're saying about MF-lenses not really having FF/BF-issues. Maybe i'm just too concerned about that red square, and doesn't pay enough attention to whats in the viewfinder. I will try to turn of the square and see if that helps me in any way
The red square doesn't indicate focus. The hexagon in the status area of the viewfinder does. The red square simply shows you where the camera is looking for focus.

01-11-2012, 05:10 PM   #5
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QuoteOriginally posted by morpho Quote
Ah, thanks

When i think about it, a bit harder than whats good for me i suppose, i see what you're saying about MF-lenses not really having FF/BF-issues. Maybe i'm just too concerned about that red square, and doesn't pay enough attention to whats in the viewfinder. I will try to turn of the square and see if that helps me in any way
I am new to Pentax too, and it was hard for me to realize that blinking red light means you are close to the focus, the beep and showing of green hexagon at the bottom right mean the focus is spot on, sometimes it happens with me and my M lenses, you just bypass it and the green hexagon light is on and then off again, but the red light is blinking because it still searches and it is close after it.

I plan to buy Pentax O-ME53 Magnifying Eyecup and at some point probably will buy and replace the focusing screen K3 one.

For your K-5:

http://www.focusingscreen.com/index.php?cPath=25_113&osCsid=d3b7bc5df7fb4d458d6d0f3e47aa0239

For now I just use live view with magnifying x4 in LCD, however I do not like live view, it slows down the camera shots and depletes battery fast, and slows processing too.

Last edited by Wolfie665; 01-12-2012 at 06:01 AM.
01-11-2012, 05:15 PM - 1 Like   #6
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If you plan to do much manual focusing, give thought to installing a focus screen that is designed for manual focusing; the stock AF screens suck. And consider turning the dadblasted red square off. I've never found it to be other than an annoyance at best or a false friend at worst.
01-11-2012, 06:11 PM   #7
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Thanks for the replies!

Wolfie: Ah, yes, thats exactly how it is for me as well, most of the time, with the red square being there, and the hexagon blinking on and off. Well, that explains a great deal. Will look into the focusing screen, but won't the magnifier eyecup mess with what you see in the viewfinder is smaller, or narrower, than what ends up in the picture?

Mike: Tried turning off the damned red blinking thing, and lo and behold, i frontfocused less, but not perfect. When using liveview and 4x mag, i focused correctly. But why does AF fine tuning have an impact on MF lenses? Or perhaps i'm just imagining things. When you say a focusing screen designed for manual focus; do you mean the same thing wolfie is talking about, from focusingscreens.com?
01-11-2012, 06:46 PM   #8
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I use screens from Katz-Eye, but you can choose from many different sources. Practically anything beats the stock screen.

01-12-2012, 01:28 AM   #9
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QuoteOriginally posted by Adam Quote
Manual lenses don't truly have front/back focus issues, as AF confirmation is approximate and there's no AF motor to bring the lens's focus to the middle of the range.

As far as testing your lenses go, you should try using the technique described here: Fixing Front and Back Focus - Introduction - PentaxForums.com

If all your AF lenses are off by that much, chances are it's your camera's fault.
Any lens can have true front/back focus issues. Different apertures can result in different planes ofoptimum sharpness...

Regarding the original question - proceedings to solve all problems. It appears that your camera AF is off. You can either apply a global fine adjustment correction for all lenses or individual adjustments for all lenses that transmit a lens ID to the camera. Your manual glass will probably not transmit lens ID infortmation so you will probably end up using a global setting for all lenses. That said, your camera should not be off by 10 steps. It requires service, so you can basically start around 0 and not at the high/low end (debug software, discussing in this forum, will allow yout to make this adjustment yourself, but care should be taken). Even with a global correction setting, you can still evaluate the fine adjustment individually, but you need to set the values manually - prone to errors (what about a firmware option for setting AF adjustment for manual lenses in addition to focal length...).
Not ready yet! Fixing the AF trouble does not mean that you have fixed on screen manual focussing trouble. A misalignment of the screen for manual focussing independent of the AF sensor is possible. You need to check this as well and may have to order shims for fine adjustment. Typically more care is taken in positioning the screen as manual shimming can be a pain, but you never now. In case you are working with the focussing eyecup, amek sure to set your screen right.

Several reports in the last couple weeks have shown that K5 cameras were off by the maximum settable offset. This should not happen. Did I say that the red squares in the viewfinder can also be off - the red square is a projection based on where the AF sensor should be, but that does not ensure that it is where it is supposed to be. The real position can be off by +/-1 square in any direction...

AF fine tuning allows manual foucsing based on the focus control lamp in the viewfinder. Real manual focussing requires screen based focussing.

Last edited by zapp; 01-12-2012 at 01:33 AM.
01-12-2012, 01:38 AM   #10
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QuoteOriginally posted by morpho Quote
Right smack bang in the middle, and i'm happy as Larry. Almost. Because, if the apply to all and apply to one is cumulative, then it means ALL my lenses are off by between -10 and -12.
They are NOT cumulative.

apply-all set to -2 and apply-one set to -2 for your 55-200 should give the same result for that lens.
01-12-2012, 04:05 AM   #11
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QuoteOriginally posted by morpho Quote
Thanks for the replies!

Wolfie: Ah, yes, thats exactly how it is for me as well, most of the time, with the red square being there, and the hexagon blinking on and off. Well, that explains a great deal. Will look into the focusing screen, but won't the magnifier eyecup mess with what you see in the viewfinder is smaller, or narrower, than what ends up in the picture?
Yes magnifier cup will make it a little bit smaller, but focusing clarity outweights the invovenience. There are different magnifiers and attachment you can use too, but most of them magnify and do the screen smaller then O-ME53, and if you wear a glasses as me are not convenient to use, because of the biggest round eye cup they have got. O-ME53 is the best for glasses.

Here is one attachment: https://www.pentaxforums.com/accessoryreviews/pentax-magnifier-fb.html

see this: Pentax Focusing Aids

The guy has a lot of Pentax lens and other information.

Here are our forum reviews here: https://www.pentaxforums.com/accessoryreviews/category-Viewfinder-Attachments-Third-Party.html

The problem with all attachments is do you really want your camera to get bulky and also I personally prefer to buy some new lens then spend 200 USD for some attachment - LBA :-)

Last edited by Wolfie665; 01-12-2012 at 04:24 AM.
01-12-2012, 04:17 AM   #12
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Thanks again all,

i did some more testshots this morning before going to work, and this time i tried to be as accurate and patient as possible, firing several shots, and if it wasn't in focus, i tried to think about if i were doing something wrong rather than the camera. I also turned off the red square. What i found out is that the focus confirmation hexagon isn't necessarily dead accurate; there are room for tiny adjustments while the hexagon is still showing. On my slower lenses this didn't seem to matter all that much, but on the 50@1,7 and the 28@2,8 it was a noticeable difference. I think...anyway, after this morning it all looks a bit better; i reset all my AF fine adjustment settings, and ended up with:

Apply to all: 0
18-55: -5
50-200: -2

It's not dead accurate, but this i put down to even more user errors, for example, the charts i printed out are bulging and aren't completely flat, so i will glue them on a piece of cardboard this evening and see if that makes a difference.

For my manual lenses, i think getting rid of the square and daring to trust my eyes instead of the hexagon proved to make the biggest difference, in addition to actually thinking about what was going on and what i was doing instead of just searching in panic for the red square and fire away.
My eyes still frontfocuses a bit, if i can say it like that, but i'll have to experiment some more.

Thanks for all the input, and i think i will be investing in a screen from focusingscreen.com. Only question is if i want it with the frames or completely blank...
01-12-2012, 05:19 AM   #13
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I got my Katz-Eye with rifle scope crosshairs.

Make sure your diopter is adjusted correctly.
01-12-2012, 05:48 AM   #14
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With 'adjusted correctly' you mean finding the right set of shims?
01-12-2012, 02:28 PM   #15
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QuoteOriginally posted by morpho Quote
With 'adjusted correctly' you mean finding the right set of shims?
I should be ashamed of myself for writing that last post do poorly.

I meant you should make sure the little adjustment slide above the viewfinder is in the right position to jibe with your eyeball. It's one of the easiest things to forget to do and having it out of adjustment can make focus look wacky.
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