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12-10-2013, 06:40 AM   #1
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How does manual arperture work exactly?

Hello everyone.

I have a quick question concerning film-era lenses with manual aperture. According to the lens database, all Pentax M lenses belocg to this class, the Pentax A lenses already have automatic ones, right?
Now, having an manual aperture, I set the aperture ring to the desired value. By doing so, is it already closed, darkening also my viewfinder or does it only close for exposure and I have the maximally bright image in my viewfinder?

OK. Here's another one: If I understand correctly, I can dial the aperture value for Pentax A lenses in my digital camera (K5II for instance) and it is written in the EXIF-data. Is that right?

Please forgive my lack of knowledge. I'm so digital native

Thanks a lot in advance

12-10-2013, 07:01 AM   #2
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https://www.pentaxforums.com/forums/54-pentax-lens-articles/110657-how-use-me...k-x-k-7-a.html
12-10-2013, 07:11 AM   #3
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no more questions
12-10-2013, 07:17 AM   #4
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Check out the guide posted above. It tells you what you need to do to use any applicable lens on a pentax digital.

As for what's manual and what's automatic, The answer isn't quite that simple. Generally there are two forms of automatic aperture:
The first one is where the camera can close the aperture so that it's open when you frame and focus but closed when you take your picture. Pentax K and M fall into this category (except, as I recall, for some long teles in the K series)
The second type of automatic aperture is where in addition to being able to close the aperture, the camera can also set it. If you want to shoot in shutter priority or program, you need this. Pentax A and forwards will give you this.
One thing that will mess this up a bit is that you can not shoot aperture priority with an M or K lens. Not because the lenses don't support it, but because the camera doesn't. They used to, but since the *ist series (and henceforth, including all digitals), the camera can't know the setting of the aperture ring.

Any lens that don't have these automatic functions is considered fully manual. adapted lenses fall into this category, but other lenses are fully manual as well, including presets, mirror teles, homemade lenses, reverse-mounted lenses, lensbabies, etc.

12-10-2013, 07:18 AM   #5
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QuoteOriginally posted by mathias2784 Quote
Hello everyone.

I have a quick question concerning film-era lenses with manual aperture. According to the lens database, all Pentax M lenses belocg to this class, the Pentax A lenses already have automatic ones, right?
Now, having an manual aperture, I set the aperture ring to the desired value. By doing so, is it already closed, darkening also my viewfinder or does it only close for exposure and I have the maximally bright image in my viewfinder?

OK. Here's another one: If I understand correctly, I can dial the aperture value for Pentax A lenses in my digital camera (K5II for instance) and it is written in the EXIF-data. Is that right?

Please forgive my lack of knowledge. I'm so digital native

Thanks a lot in advance
M lenses actually have automatic aperture, just different from A lenses. When setting the aperture on a Pentax-M lens it will still remain wide open for composing and will close to the desired opening only when releasing the shutter.
A lenses, on top of that, will communicate with your camera (if it is compatible, all DSLRs are) so it will know the aperture setting (that will be saved with the exif data only if the aperture ring on the lens is set to the A position) and also for use of Tv mode and setting the aperture through the camera controls.

One thing you need to insert manually to the camera with all manual lenses is the focal length. That's for the SR but it will also be saved with the exif data.
12-10-2013, 07:19 AM   #6
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QuoteOriginally posted by mathias2784 Quote
no more questions
I guess I write too slowly
12-10-2013, 07:28 AM   #7
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QuoteOriginally posted by Pablom Quote
I guess I write too slowly
Absolutely no problem. This thing about FL was new to me.
12-10-2013, 07:36 AM   #8
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Maybe another, more personal question:
How do you manualists focus on a DSLR like K5? I mean do you use aids like VF-magnifier, the focus-lock-beep, or maybe split prism focus screens?
A friend of mine borrowed me some old canon (I think it's called AE-1) and focusing with split-prism is quite easy and enjoyable, even for an AF-spoiled child like me .
Browsing the internet, the only thing I find for Pentax DSLRs is Katzeye. But these cost ~200 EUR incl. shipping to Europe. Are they they worth it or just another way to spend some money?

12-10-2013, 07:42 AM   #9
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There are other options for the split-prism focus. Jinfinance (I think) is who I got mine from. They have various screens available. Do a forum search for focus screen and you should find the info.

The split focus screen brings some quirks with it, but the modification worked well on my K-10D. If I get a K-3 I may put a split screen in my K-5.
12-10-2013, 08:02 AM   #10
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QuoteOriginally posted by mathias2784 Quote
Maybe another, more personal question:
How do you manualists focus on a DSLR like K5?
I just use Catch-in-focus. It's basically the poor man's autofocus. It's center spot only, so for trickier focusing I switch the camera to MF and just eyeball it with the stock focusing screen or use live view.
12-10-2013, 08:04 AM   #11
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QuoteOriginally posted by mathias2784 Quote
Browsing the internet, the only thing I find for Pentax DSLRs is Katzeye. But these cost ~200 EUR incl. shipping to Europe. Are they they worth it or just another way to spend some money?
Focusing Screen

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12-10-2013, 09:04 AM   #12
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QuoteOriginally posted by mathias2784 Quote
Now, having an manual aperture, I set the aperture ring to the desired value. By doing so, is it already closed, darkening also my viewfinder or does it only close for exposure and I have the maximally bright image in my viewfinder?
When using M42 lenses, the viewfinder will indeed darken. So you focus with widest aperture, close the aperture to the desired value, set shutter for correct exposure and you take the shot.

QuoteOriginally posted by mathias2784 Quote
How do you manualists focus on a DSLR like K5? I mean do you use aids like VF-magnifier, the focus-lock-beep, or maybe split prism focus screens?
On the K5, I use a combination of the hexagon / beep and the view finder; no additional tools. It seems to work quite well if I cheat a little by not using the widest apertures You also have to get used to the behaviour of the hexagon; there is not an exact point where the hexagon indicates in-focus but a small range and it requires a bit of practicing / experience to find the exact point.
On the K100D and K10D, I use a split prism screen.
12-10-2013, 01:42 PM   #13
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QuoteOriginally posted by mathias2784 Quote
How do you manualists focus on a DSLR like K5?
Canon EE-S screen cut down to K-5 size by focusingscreen.com. Pentax O-ME53 viewfinder enlarger. I use it with glasses and can still usually hit targets on an 85 f/1.4.
12-10-2013, 02:02 PM   #14
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To summarize the above and provide some additional here are the bullet points regarding lens aperture types:
  • Fixed: The lens has no adjustable aperture. This is the norm for mirror telephoto lenses.
  • Manual: Aperture is always stopped down. This is the norm for cameras lacking TTL viewfinders and view cameras. With a few exceptions (e.g. current Mitakon lenses), manual aperture lenses are rare for SLR use.
  • Preset: Aperture can be preset to a desired stop while the diaphragm remains fully open for focusing. Stop-down for exposure is done with a second ring or switch on the lens barrel. Commonly found on various vintage lenses. A common example would be the Russian Jupiter-9 85/2 in M42 mount.
  • Semi-Automatic: The lens features a coupling mechanism that allows the camera to stop the lens down to a preset f/stop at time of exposure. Reopening the lens requires use of a lever on the side of the lens. A good example would be the misleadingly-named Auto-Takumar lenses from the 1950s.
  • Automatic: Lens has a coupling mechanism that allows the camera to stop the lens down to the preset f/stop at time of exposure. The lens reopens automatically after the exposure. Almost all modern SLR lenses and most vintage examples feature automatic apertures. At one time, auto-aperture was a big selling point and many vintage lenses are prominently labeled as such (e.g. Auto Rikenon, Auto Yashinon, Auto Mamiya/Sekor, etc). Some auto-aperture lenses have a mechanism that allows for full-manual aperture use. This is the case for most M42 lenses.
  • Automatic Aperture Control: This is the official name for the Pentax lens/camera feature that allows the aperture to be controlled by the camera body. Lenses that support this feature have auto-aperture along with a set of contacts on the mount face (the "A" contacts) that provide information regarding maximum/minimum aperture to the body. If an aperture ring is present, there is a prominently labeled "A" position on the scale of that ring. AKA "A" contact lenses.
Probably more than you care to know.


Steve

Last edited by stevebrot; 12-10-2013 at 02:14 PM.
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