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07-28-2018, 10:03 PM   #1
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Manual Focus Lens Use Question

I started with the Pentax ME Super in 1983, and have an old 28mm f/2.8 lens that I still use today with my K-5, and I use it on TV mode, i.e. aperture priority mode, and it works good.

I persuaded my nephew to give me the 50mm f/1.7 lens my dad used on his old Pentax ME Super. Dad delivered it to me last week, and I used it on TV mode, but the results were awful. I reviewed the EXIF and saw that indoors at f/1.7 or slightly above, the shutter speed was way too fast, as in 1/800, and 1/640. The images were blurry, orange, and unusable.

Tonight I experimented in manual mode and was able to get a decent image in limited light by slowing the shutter speed, and setting the ISO a bit higher, and putting the aperture near f/1.7 or f/circa 2.4.

I looked in the lens, and I see sort of bubbly material but no fungus.

Why won't it work in TV aperture priority mode, whereas my equally as old f/2.8 28mm lens does work in TV mode?
I experimented tonight to see if I could figure out if it is the settings, or dirt in the lens. The first photo is in TV mode. The second photo is after I experimented in manual mode. (I am not proficient yet at manual mode - my ME Super spoiled me).

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07-28-2018, 10:13 PM   #2
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This is my KMart Focal f/2.8 lens in aperture priority mode (TV mode). I set the aperture at f/2.8 on this lens. The Pentax f/1.7 glass when new would be much better.

---------- Post added 07-29-18 at 12:17 AM ----------

Am I doomed to having to entirely learn manual settings?
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07-28-2018, 10:27 PM   #3
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First off, the focus seems to be varying wildly - is there glass in front of that clock face? You might be focusing on reflections.

Secondly - with a manual lens you need to use manual mode, then set the aperture, then hit the green button to get the 'suggested' exposure. It's a specifically pentax thing, you can't use Tv to set the shutter speed, there is no auto with a pentax using a manual lens.

Pentax Green Button Guide - Articles and Tips | PentaxForums.com

try;
Camera in manual mode.
ISO to 400 (or whatever value you choose)
Set lens to f 5.6 (using the metal dial on the lens)
focus
hit green button whilst focused.
then take photo.

In practice it doesn't take much time when you are used to how it works.
07-28-2018, 10:43 PM   #4
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Assuming the lens is not an "A" series, e.g. no electrical contacts then all modes will default to Av except M, B and X. Stop-down meter with the green button or optical DOF preview should be used in M mode. Menu settings should be in effect: Use Aperture Ring - enabled, DOF Preview - optical, Green Button in TAv and M - Tv shift.

Refer to the following threads:

Manual Metering on Pentax DSLRs with Manual and Automatic Lenses - PentaxForums.com
How to use/meter Manual & M42 Lenses on all Pentax DSLRs (K-1, K-3, K-5, K-30, etc) - PentaxForums.com

07-28-2018, 10:46 PM   #5
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Thank you. I will try it. But, that seems complicated. So I will need practice. The photos of my 86 year old dad were just horrible last week on TV mode and my equally as old manual lens that was lower class glass took good photos. Until tonight I was considering experimenting with taking apart dad's 50mm lens and cleaning the interior glass.
07-29-2018, 12:58 AM   #6
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Its actually quite simple. You only need to customize the green button and after that shooting fully manual will be a matter of focussing, choosing the aperture you want on the lens and then pressing the green button before pressing the schutter. I personally like this a lot as it allows me to take much more purposeful and deliberate photos. Just give it a try.
I have no idea about the bubbly stuff inside your lens. Could you post a picture? 50 mm lenses aren't that expensive, so if there's something wrong with the lens, you could just buy a better one.
07-29-2018, 01:16 AM   #7
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To keep it simple:

1. Use M mode
2. Follow these instructions: How to use/meter Manual & M42 Lenses on all Pentax DSLRs (K-1, K-3, K-5, K-30, etc) - PentaxForums.com
(TLDR: select aperture via ring -> focus -> green button -> shoot)

Metering requires an additional step on digital because digital cameras cannot sense the position of the aperture ring.

For the most consistent metering performance, use live view.

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07-29-2018, 01:29 AM   #8
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The old lenses with no "A" setting , will only work fully in Manual exposure mode after you have set the "allow use of aperture ring" setting.

You can use them in Av mode (not Tv mode) which is aperture priority. But they will always capture at widest aperture irrespective of the lens setting. If you try and set Tv mode or P mode the camera will default to Av mode.

07-29-2018, 01:37 AM   #9
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For me, I had to adjust the green button function in the menu, then the above procedure worked perfectly.
07-29-2018, 02:41 AM   #10
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Can you provide a shot of the lens itself, showing the 'bubbly' material you mentioned? Could be there's a problem inside the lens you won't overcome with exposure adjustments no matter how hard you try.
07-29-2018, 07:28 AM   #11
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Just note to add that if you use live view, you still need to press the green button to meter the lens with the set aperture. The use of live view is not noted in the link provided.
Also, if you use Tv mode with only f5.6, then I believe you get correct exposure since the metering is done at f5.6.
07-29-2018, 08:37 AM   #12
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QuoteOriginally posted by buzzinhornet Quote
Also, if you use Tv mode with only f5.6, then I believe you get correct exposure since the metering is done at f5.6.
For manual lenses that won't work. Setting the camera to Tv mode will cause the camera to default to Av mode. The picture will be correctly exposed but at the lens's maximum aperture.
07-29-2018, 09:40 PM   #13
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QuoteOriginally posted by sqrrl Quote
First off, the focus seems to be varying wildly - is there glass in front of that clock face? You might be focusing on reflections.

Yes. There is glass in front of the clock face. Numbers on the right side of the clock face have worn or faded black paint.

---------- Post added 07-30-18 at 12:30 AM ----------

QuoteOriginally posted by HoutHans Quote
Its actually quite simple. You only need to customize the green button and after that shooting fully manual will be a matter of focussing, choosing the aperture you want on the lens and then pressing the green button before pressing the schutter. I personally like this a lot as it allows me to take much more purposeful and deliberate photos. Just give it a try.
I have no idea about the bubbly stuff inside your lens. Could you post a picture? 50 mm lenses aren't that expensive, so if there's something wrong with the lens, you could just buy a better one.
Sorry, I am not sure I can photograph it. I don't know if I could hold everything in position to do so, and today, I can't see what I thought looked like tiny dot sized bubbles a few days ago.

I am using the suggestions regarding the green button, and I think they work but my photos are not as sharp as I would expect, and I did better setting my own manual settings when I posted my photos of the clock with the 50mm lens (center photo).

I wasn't aware of the green button before you gave me your collective advice on its use. I will experiment in the future with people rather than clocks.
07-30-2018, 10:38 PM   #14
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Great, I really hope you'll enjoy it and get that lens sorted.
08-01-2018, 10:27 PM   #15
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I practiced on two guinea pigs, mom and dad. And, either they, or I did fairly good. Not great. But, fairly good. A bit overexposed but considering I had it on camera setting "M" it was good for me.

---------- Post added 08-02-18 at 12:29 AM ----------

Is the lens serviceable?
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