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06-05-2012, 11:55 AM   #1
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Using manual focus lens

I have a K-r and I recently acquired an old 50mm Takumar f2.8 M42 lens that I have been playing with. I have figured out that to get a sharp focus you must get the little green hexagon to show up in the viewfinder. This works like a charm until I get past f8. Then the hexagon refuses to show up and there is no way to focus except by eyeball and sheer luck, which usually doesn't turn out too well for me. I've tried all sorts of settings and combinations to get it to work, but it will not. Is this normal and is there a way to work around it?

06-05-2012, 12:02 PM   #2
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The green hex is a good indicator but be aware it has a range of "in focus" that can be wider than reality. So sometimes the hex will light up but you will still not be quite right, this is most prevalent at wider apertures (f/2.8 and wider).

The reason you have issues at f/8 and smaller is that not enough light is hitting the AF sensor which is what activates the green hex. To get around this, focus with the lens wide open (f/2.8) and then stop down to the aperture you want to use. You get used to counting clicks as you turn the aperture ring so you do not have to remove the camera from your eye.
06-05-2012, 12:04 PM   #3
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Less light as you stop down = focus assist can no longer determine focus. Basically though, you shouldn't be focusing at f8. You should focus wide-open, which will actually help you pinpoint where the focus plane is because it will be narrower than at f8 and the viewfinder will be a lot brighter. Then stop-down to snap the shutter. With all of your non-m42 lenses (manual or auto focus), that is also what you are doing (focusing wide-open), but the stopping-down is handled automatically.
06-05-2012, 12:23 PM   #4
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Yes, as stated above, the correct sequence would be 1. focus (2. stop down) 3. meter 4. shoot. Elementary, son
By the way, what 50mm f/2.8 Takumar do you have?

06-05-2012, 12:30 PM   #5
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QuoteOriginally posted by kcobain1992 Quote
By the way, what 50mm f/2.8 Takumar do you have?
Yes, inquiring minds want to know.....................
06-05-2012, 12:50 PM   #6
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Okay, thanks, this is very helpful. Actually it is an f2, not a 2.8. It is an SMC Takumar 1:2/55. I bought an old Honeywell Pentax SP1000 at an auction a few weeks ago for $5 and this is the original lens that was on it. It's certainly a lot more trouble to use than the kit lenses, but it gives a nice sharp picture when I do it right.
06-06-2012, 03:40 AM   #7
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split sreen and microprism

In my K-100D to try to solve the problem I bought a new focusing screen with microprism and a split screen diagonal in it.
I found it really good for the price (you can find many of then for about 20-30$ ...) in particular if you shoot often wide open.
Bye.
06-06-2012, 05:12 AM   #8
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Yes, that's a good tip, but it doesn't solve the issue of focusing at f/8. And the green hex works just as well, if you have few MF lenses and you're patient.

06-06-2012, 07:38 AM   #9
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If the lens is an SMC Takumar then it should have the auto/man switch between the aperture ring and the lens mount.

Set the camera to Manual Focus (MF) - the focus confirmation hex will indicate at lower apertures but you will still be able to take an exposure when it is not lit.

Slide the switch to auto (the word AUTO should be fully visible) - aperture should be wide open no matter what the ring is set to. Focus. Slide the switch to the manual position. Stop down meter, setting your aperture to what you want f8 or greater in this case. Take your exposure.

The procedure becomes second nature in a very short time.

I'm guessing you've read this thread on using and metering with manual and M42 lenses.

If it doesn't have the switch then you have to use the sequences mentioned above.
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