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04-11-2011, 03:43 PM   #1
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First time use of 50mm f/1.7 - focusing?

I have recently acquired the Pentax-A 50mm f/1.7. I had read discussions about "front focus" or "rear focus" and was wondering best practice.

As a manually focusing lens, I do get a confirmation tone from the camera when an image is "in focus". What I would appreciate some education on is whether it makes a difference to be coming in from infinity or out from 0.45m when trying to acquire focus.

Thank you for your time and patience.

04-11-2011, 06:03 PM   #2
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I have not noticed a difference in either direction. I usually overshoot and back into again slowly. At my age and with my eye sight + the poor screen, the beep does better than I can.

For long shots hyper-focal manually set is all you need.

Hey, it don't cost nothing for digital viewed on a monitor. Try it all ways and let us know what you decide.
04-11-2011, 07:47 PM   #3
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Front focus and rear focus (I assume you're talking about front focus problems and rear focus problems) per se doesn't happen with a manual lens.
Rear and front focusing only happens with an AF lens, being the reason why there are in-camera adjustments. It is also the camera focusing by itself (automatically) why there is at times these problems.
With manual focusing, YOU are the one focusing, so any mistakes are your own and not the equipment's.
With regards to help in focusing with manual lens, I just rack it back and forth to find the best focused image according to my eyesight.
If the camera is not set to "MF" then it will always wait for focus confirmation before it fires (application is "trap focus").
If you set the camera to "MF" then even if the focus is off, the shutter will fire once you trip the shutter.
04-11-2011, 11:48 PM   #4
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A split-prism focusing screen will help to some degree, but IŽd suggest trying your hand without it first. Whether the exact focus is best met coming in from infinity or going out will depend on the tiny peculiarities of your camera & your lens. Try it & see what results you get. Learn which is best & how much you can trust the focus confirm indicator.

You should focus bracket anyway with a lens that fast, try to take several with slightly different focus, this should greatly increase your keeper rate.

04-12-2011, 12:41 AM   #5
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A split-prism focusing screen does help by let me know if you turn/focus the lens in the wrong direction. The in-focus indicators (beep and hexagon in VF) do help a lot, and I need to move a bit to reframe before shot.

The closer the subject, the more difficult to focus, due to larger turn distance on the lens, and DOF is thin. Each manual lens has different turn distance. The A50f1.7 has 'sensitive' focus ring and also difficult to get in-focus indicator to work in dim light.
04-12-2011, 03:28 AM   #6
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Appreciate the feedback

I have only had the K-x for about 6 months and almost everyday I am reminded of how and why I am a novice...

I totally forgot to switch to MF and was getting TREMENDOUSLY frustrated having to wait for the camera's tone.

Thanks again!
04-12-2011, 05:58 AM   #7
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Let me throw another wrench into your works. Once you get use to focusing in manual focus mode, go to your custom menu and turn on Catch In Focus. Then put your camera back in to AF-S focus mode. Hold down your shutter button completely and turn the focus ring (rather slowly) until the camera takes a picture.

04-12-2011, 09:22 AM   #8
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I have that same lens with my K-x, it is a real learning experience to get in-focus shots. I have been surprised by how difficult it is to catch a good shot, especially way down at f/2.8 or wider. But when you do the lens works surprisingly well. Although the 50mm f/1.7 costs maybe 30% of my next cheapest lens I think it's been the most fun.

04-14-2011, 06:21 AM   #9
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Spectacles (Glasses) off?

Hello, I am interested in knowing how to manual focus properly. I am using a K-r

I currently wear specs for short sightedness (around -2 to -2.5). I found that through the viewfinder, with the diopter slider all the way to the right, I have the same "view" with/without the glasses.

At this diopter setting, I find that I need to have both eyes open (one through the viewfinder, one looking straight ahead outside of viewfinder), to be able to get the sharpest (still not sharp enough in my opinion) possible info bar and the boxes in the viewfinder.

I might be totally wrong on how to see through a viewfinder. Do I wear my specs or specs off? Please do correct me. Thank you.
04-14-2011, 07:09 AM   #10
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I found with a little practise I could focus my old manual focus zoom lenses using the live view screen - I was using them for shots taken on a tripod. I should investigate the MF setting with the tone. I wear glasses for short sight, I look over them at the screen.
04-14-2011, 08:45 AM   #11
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When I got my first dSLR about 3 years ago, I hadn't shot a SLR or TLR in almost 3 decades, hadn't manually focused a rangefinder or anything in over 15 years. And my eyeballs are sadly de-laminating behind my thick glasses. But I have no trouble focusing fast / thin-DOF manual lenses. Yes, I have assistance -- I ordered a KatzEye-type screen at the same time as my K20D, and I exploit focus confirmation and CIF. I use CIF a lot. Trouble with a 50/1.7? Pshaw -- DOF on a 300/3.5 is about twice as thin, much less leeway, but it's no bother. All I can suggest is: practice practice practice. And use a split-screen, focus confirmation, and CIF.
04-14-2011, 02:54 PM   #12
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QuoteOriginally posted by yanzhi0714 Quote
Hello, I am interested in knowing how to manual focus properly. I am using a K-r

I currently wear specs for short sightedness (around -2 to -2.5). I found that through the viewfinder, with the diopter slider all the way to the right, I have the same "view" with/without the glasses.

At this diopter setting, I find that I need to have both eyes open (one through the viewfinder, one looking straight ahead outside of viewfinder), to be able to get the sharpest (still not sharp enough in my opinion) possible info bar and the boxes in the viewfinder.

I might be totally wrong on how to see through a viewfinder. Do I wear my specs or specs off? Please do correct me. Thank you.
I usually take my glasses off and use my left eye through the viewfinder cause I'm basically blind in my right eye and I don't use a Katz eye etc but rely pretty much on the camera indicators, so far so good...

It just takes tons and tons of practice to get manual focusing just right plus knowing your camera and different lenses. I personally focus from the infinity end, I've found this is the most accurate. Lots of sharp fast lenses will lag a little before the camera indicator finally kicks in (due to depth of field etc), so when you can see your getting close, slow down and give the camera a chance. Go back and forth, till your pretty sure...

I practice on a newspaper, making sure I point the camera to a specific word, take a shot, and take a quick look. You might find you had the camera pointed at a slightly different location than you intended, etc. so just practice practice practice.

Good luck...
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