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02-20-2014, 08:30 AM   #1
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Focusing Problem With my Pentax-M 50mm 1.4f

Hi
I am using Pentax-M 50mm f1.4 on Pentax K-10D
I bought this lens(Pentax-M 50mm f1.4) 15 days ago..I am having problem with its focusing how much I try I am not getting the perfect focus..And many times there were ghost on the edge of the subject...I am clicking my shutter down when the subject is on focus in my viewfinder ,when I hear the beeping sound of focus of my camera and the red square in the middle of the viewfinder..I am not getting perfect sharpness or maybe this is the best sharpness that this lens can deliver I am not sure..
I am posting some pictures I have taken with best focus that I could..If any one using this lens with Pentax K10D please tell me if there is a way to get better sharpness and perfect focus.. And also please share if there is any better focusing techniques...Thank You...

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02-20-2014, 08:59 AM   #2
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Hi! Manual focus is not easy with (older) digital bodies. Many people changed their stock focusing screens for being able to do precise manual focusing.
The M 50 f1.4 is a fine lens, you should be able to take sharp photos. I don't know at what aperture you were shooting, but be aware that wide open, or even closed a few stops the depth of field is so thin that if you move just a little between focusing and pressing the button you're already out from the focus plane. For the first two photos you've been shooting with low shutter speed even if you have SR on (better set higher ISO and have some grain than blur).
That can be the reason for the images being not that sharp. On the other hand your first photo doesn't look unsharp, just that your focus point is somewhere on the edges of the glasses, and your DOF is very small. It takes some time to practice to use manual lenses. I've tried on my K10D, K20D and it's not easy, but it's fun! (a little bit of hit and miss...) Good luck

Last edited by Caver; 02-20-2014 at 09:00 AM. Reason: typo
02-20-2014, 09:00 AM   #3
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As a suggestion, enable Catch-In-Focus and turn the focusing ring very slowly. It might be technique - I know that when I turn the ring manually, I tend to overshoot. You might have to look up CIF in your manual. On my K10D it's as simple as putting the camera into AF.S and holding down the shutter release fully, but I think later models need to have a menu option selected.
02-20-2014, 09:02 AM   #4
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Wide-open it's really hard to nail the focus. Live view would certainly help if you had it, but use DOF to your advantage otherwise.


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02-20-2014, 09:32 AM   #5
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Hi,
Welcome to the Pentax Forums. Manual focus with fast lenses is a bit of an challenge with most dSLR cameras regardless of brand. This is true even when using the AF system to provide focus confirmation. I shoot with a K10D and feel your pain. There are multiple factors at work here:
  • The AF system has poor precision when used with faster glass. This is true regardless of AF mode or how the system is used (AF, focus confirm, or catch-in-focus*).
  • The area for any of the AF focus points in the viewfinder is fairly large with obvious side-effects for three-dimensional subjects when DOF is shallow.
  • The stock focus screen is poorly designed for straight manual focus
Any of the above points can be explained in great detail, but for now please take all three as being true.

What you can do:
  • When using AF confirm, switch to the center focus point. Doing so will give you more control over what you intend to be in focus.
  • Shoot at narrower apertures to increase depth-of-field
  • Practice your manual focus technique using simple subjects and a tripod
  • Consider upgrading to an aftermarket focus screen designed for manual focus. I use a screen with combined split-image/microprism focus aids. Other users have found that various fine-matte screens work well.
Regarding your Pentax-M 50/1.4:
  • It is a very good lens with solid build and sound optical design
  • As with all f/1.4 lenses, DOF is very shallow when shooting wide-open
  • It is somewhat soft wide open


Steve

* Catch-in-focus (CIF) is an undocumented feature of your camera where the shutter will not release in AF-S mode until the AF system has acquired a focus lock. As noted above, it involves pressing the shutter release and moving the focus ring, subject, or camera until focus is acquired and the shutter releases. It is sort of fun, but I have not found it suitable for fine focus.

Last edited by stevebrot; 02-20-2014 at 09:43 AM.
02-20-2014, 10:21 AM   #6
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QuoteOriginally posted by Canada_Rockies Quote
As a suggestion, enable Catch-In-Focus and turn the focusing ring very slowly. It might be technique - I know that when I turn the ring manually, I tend to overshoot. You might have to look up CIF in your manual. On my K10D it's as simple as putting the camera into AF.S and holding down the shutter release fully, but I think later models need to have a menu option selected.
Thank you Canada_Rockies
I have tried CIF its easy but it gives very bad results during low aperture mainly at f1.4...I am very fond of bokeh that is why I let my aperture wide open..I have to take some portraits in high aperture to check it.. Thank you for your help..I rally appreciate it..

---------- Post added 02-20-14 at 11:00 PM ----------

QuoteOriginally posted by Caver Quote
Hi! Manual focus is not easy with (older) digital bodies. Many people changed their stock focusing screens for being able to do precise manual focusing.
The M 50 f1.4 is a fine lens, you should be able to take sharp photos. I don't know at what aperture you were shooting, but be aware that wide open, or even closed a few stops the depth of field is so thin that if you move just a little between focusing and pressing the button you're already out from the focus plane. For the first two photos you've been shooting with low shutter speed even if you have SR on (better set higher ISO and have some grain than blur).
That can be the reason for the images being not that sharp. On the other hand your first photo doesn't look unsharp, just that your focus point is somewhere on the edges of the glasses, and your DOF is very small. It takes some time to practice to use manual lenses. I've tried on my K10D, K20D and it's not easy, but it's fun! (a little bit of hit and miss...) Good luck
Thank you Caver
Your words are making quite sense..I am very fond of bokeh that is why I let my aperture wide open..Mainly 1.4..Next time I will take photos at larger aperture..I always had a feeling that my lens could have had haze that is why my pictures were all out of focus...But it it seems now the problem is in the individual focusing technique..Thanks a lot for your reply..




---------- Post added 02-20-14 at 11:09 PM ----------

QuoteOriginally posted by stevebrot Quote
Hi,
Welcome to the Pentax Forums. Manual focus with fast lenses is a bit of an challenge with most dSLR cameras regardless of brand. This is true even when using the AF system to provide focus confirmation. I shoot with a K10D and feel your pain. There are multiple factors at work here:
  • The AF system has poor precision when used with faster glass. This is true regardless of AF mode or how the system is used (AF, focus confirm, or catch-in-focus*).
  • The area for any of the AF focus points in the viewfinder is fairly large with obvious side-effects for three-dimensional subjects when DOF is shallow.
  • The stock focus screen is poorly designed for straight manual focus
Any of the above points can be explained in great detail, but for now please take all three as being true.

What you can do:
  • When using AF confirm, switch to the center focus point. Doing so will give you more control over what you intend to be in focus.
  • Shoot at narrower apertures to increase depth-of-field
  • Practice your manual focus technique using simple subjects and a tripod
  • Consider upgrading to an aftermarket focus screen designed for manual focus. I use a screen with combined split-image/microprism focus aids. Other users have found that various fine-matte screens work well.
Regarding your Pentax-M 50/1.4:
  • It is a very good lens with solid build and sound optical design
  • As with all f/1.4 lenses, DOF is very shallow when shooting wide-open
  • It is somewhat soft wide open


Steve

* Catch-in-focus (CIF) is an undocumented feature of your camera where the shutter will not release in AF-S mode until the AF system has acquired a focus lock. As noted above, it involves pressing the shutter release and moving the focus ring, subject, or camera until focus is acquired and the shutter releases. It is sort of fun, but I have not found it suitable for fine focus.
Thank you Stevebrot Thank you for you reply..I really appreciate it..
I will keep your points in my mind..I never uses narrower aperture I really liked the bokeh feeling but from now on I think I have to get used to narrow aperture...

Last edited by tezomoy; 02-20-2014 at 10:33 AM.
02-20-2014, 10:44 AM   #7
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The first one looks like it's in perfect focus, it's just that the depth of field is really thin and 1/15s is really low for any human model.
02-20-2014, 10:48 AM   #8
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If you want to manually focus with any accuracy, the distance between your lens and focussing screen must be exactly equal to the distance between the lens and sensor. It's very likely that this is not the case on your camera. Manufacturing tolerances, y'know. This distance is adjusted by using the correct shims. (do a forum search for focus screen shim)

Check out this diagram. For accurate focus, distance L1, L2 and L3 must all be equal.



02-20-2014, 11:03 AM   #9
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The stock focus screen is only accurate as wide as 2.4 or so. For anything wider than that you'll need to use live view or switch out the focusing screen, unless you prefer to guess.

Try using live view with the info button to zoom in. it's not bad to get stuff in focus when you can zoom to 4/6/8x. Just remember how shallow the DoF is at 1.4 at a given distance -- at 6 feet less than 3 inches are in focus. You can easily get someone's eyes in focus and have their nose and ears soft at such a high aperture. Online Depth of Field Calculator
02-20-2014, 11:24 AM   #10
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QuoteOriginally posted by narual Quote
Try using live view with the info button to zoom in. it's not bad to get stuff in focus when you can zoom to 4/6/8x.
On a K10D? Please, please, please show me how.

02-20-2014, 11:41 AM   #11
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QuoteOriginally posted by narual Quote
The stock focus screen is only accurate as wide as 2.4 or so.
Actually much worse than that. Apparent DOF is equivalent to about f/4 on the K10D. As such, the stock screen is not particularly useful for manual focus.

QuoteQuote:
For anything wider than that you'll need to use live view or switch out the focusing screen, unless you prefer to guess.
No live view or focus peaking on the K10D. There is a digital DOF preview feature that might be useful when doing tripod work, though the approach would essentially be the same as focus bracketing.


Steve

Last edited by stevebrot; 02-20-2014 at 11:53 AM.
02-20-2014, 11:43 AM   #12
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QuoteOriginally posted by sterretje Quote
On a K10D? Please, please, please show me how.

Never used one. Guess it doesn't have live view? Guess you're out of luck on that front.
02-20-2014, 12:00 PM   #13
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QuoteOriginally posted by johnyates Quote

Check out this diagram. For accurate focus, distance L1, L2 and L3 must all be equal.
This is such a great diagram and I always appreciate it when I see it. OTOH, with the stock focus screen and no live view, it is rather hard to determine if shimming would help.


Steve

---------- Post added 02-20-14 at 11:03 AM ----------

QuoteOriginally posted by narual Quote
Never used one. Guess it doesn't have live view? Guess you're out of luck on that front.
It is always good to have used the camera in question or at least be familiar with the specs (listed on this site) before offering suggestions for troubleshooting...not that I have not been guilty of doing the same thing...


Steve
02-20-2014, 01:54 PM   #14
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QuoteOriginally posted by tezomoy Quote
Hi
I am using Pentax-M 50mm f1.4 on Pentax K-10D
I bought this lens(Pentax-M 50mm f1.4) 15 days ago..I am having problem with its focusing how much I try I am not getting the perfect focus..And many times there were ghost on the edge of the subject...I am clicking my shutter down when the subject is on focus in my viewfinder ,when I hear the beeping sound of focus of my camera and the red square in the middle of the viewfinder..I am not getting perfect sharpness or maybe this is the best sharpness that this lens can deliver I am not sure..
I am posting some pictures I have taken with best focus that I could..If any one using this lens with Pentax K10D please tell me if there is a way to get better sharpness and perfect focus.. And also please share if there is any better focusing techniques...Thank You...
For the first photo you were approximately at 1 meter from your subject. At this distance, with the 50mm lens at F1.4 the DOF is approx 1,8 centimeters - which is way too small, to have at least the glasses, the eyebrow and the eye in focus...
[ No, I'm not that smart, I've used one of my favorite Android AP's, the DOF Calculator developed by aimenrg.com ]
02-20-2014, 04:49 PM   #15
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QuoteOriginally posted by sterretje Quote
On a K10D? Please, please, please show me how.

I fitted my K10D with an LL-60 screen which is much closer to the original film matte screens. It works much better, and has rule of thirds rules (?) that help keep the trees and houses standing upright without that 5 degree tilt.
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