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12-08-2011, 03:53 AM   #16
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QuoteOriginally posted by sterretje Quote
I think ferhlopez figured it out two days ago
Oh my, you're right! I should really check on the thread dates also (and posts beyond the first 5).

05-20-2012, 11:40 AM   #17
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Hi Everyone, I'm new to this forum and keen to get the most out of my Pentax K-M DSLR. I currently have the kit lense (18-55mm) but am keen to use prime lenses. So have some questions.

I have seen a few SMC Pentax-M 50mm f1.7 lenses which are obviously cheaper than the brand new DA lenses. I've seen the link on using this lense, but I would also like to set the shutter speed manually as well. Is this possible?

Also does 50mm in these lenses equate to a higher focus? i.e. if i want 50mm by modern DSLR standards do I therefore need to look for a 35mm(approximately) prime lense.

Also how does the quality of the M series (sharpness Bokeh aberation) compare with the modern AF prime lenses.

How does this compare with the A series prime lenses?
05-20-2012, 04:30 PM   #18
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@aghosh1
QuoteQuote:
I've seen the link on using this lense, but I would also like to set the shutter speed manually as well. Is this possible?
For these lenses Pentax offers the green button solution in "M" mode. As this is in fact a kind of Av, you cannot directly utilize it for Tv.
What I do in such cases, is:
  1. Set the lens to fully open
  2. Use the green button - the camera will set an appropriate exposure time
  3. Correct the exposure time to what I want, and close the aperture by as many steps as I corrected the exposure time
  4. Shoot (WITHOUT pressing the green button again!)
In case there is too much light to get a reasonable exposure time using the green button fully open, chose a smaller aperture initially - but then you have to decide whether you must increase or decrease aperture to compensate for you mods in exposure time.

If there is a better way, I am open to suggestions. I never made extensive tries. But as I have a K200 - and the K-m is a stripped down K200 - you should be able to do it as I did.

EDIT: I forgot... I don't know whether you are new to non-P&S. If so, have a look at the standards for exposure times and aperture openings. One click at the aperture ring may NOT mean one step in altering exposure time, as offered by the camera controls. I think the official values are set by an ISO standard.

Last edited by RKKS08; 05-20-2012 at 04:41 PM.
05-20-2012, 04:33 PM   #19
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QuoteOriginally posted by RKKS08 Quote
@aghosh1
For these lenses Pentax offers the green button solution. As this is in fact a kind of Av, you cannot directly utilize it for Tv.
What I do in such cases, is:
  1. Set the lens to fully open
  2. Use the green button - the camera will set an appropriate exposure time
  3. Correct the exposure time to what you want, and close the aperture by as many steps as you corrected the exposure time
  4. Shoot (WITHOUT pressing the green button again!)
In case there is too much light to get a reasonable exposure time using the green button fully open, chose a smaller aperture initially - but then you have to decide whether you must increase or decrease aperture to compensate for you mods in exposure time.

If there is a better way, I am open to suggestions. I never made extensive tries. But as I have a K200 - and the K-m is a stripped down K200 - you should be able to do it as I did.
The K-m doesn't have a green button, you use the AV+- button instead.

05-20-2012, 04:44 PM   #20
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QuoteOriginally posted by RKKS08 Quote
If there is a better way, I am open to suggestions
I absolutely detest green button metering. Its clunky and its inaccurate. You're better off shooting in completely manual mode, change aperture and shutter speed at will, use a hand held meter or a metering app on your phone for the metering.

Or just sell all that legacy glass and buy yourself a nice DA lens - support the Pentax cause, and support this forum by buying through a forum link.

Last edited by selar; 05-20-2012 at 04:51 PM.
05-20-2012, 05:14 PM   #21
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QuoteOriginally posted by aghosh1 Quote
Also does 50mm in these lenses equate to a higher focus? i.e. if i want 50mm by modern DSLR standards do I therefore need to look for a 35mm(approximately) prime lense.
50mm is 50mm

So a M50/1.7 gives the same field of view as your kit lens at 50mm. If you (more or less) want the 'classic' field of view that the M50/1.7 gives on a SLR (not dSLR), you need to look for a 35mm for your dSLR. Which will give you the same field of view as your kit lens set to 35mm.
05-20-2012, 05:17 PM   #22
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Using a genuine 'A' series (K-A, FA, DA...) lens is best as it solves a lot of metering and flash headaches with Pentax dSLR cameras. However, search this forum for a means to fool your camera into thinking your older 'M' series lens is also an 'A' series lens.
05-20-2012, 05:23 PM   #23
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@selar
QuoteQuote:
Its clunky and its inaccurate.
This is probably body and lens related. With my K200 I don't have problems in accuracy (percentage of wrong exposures small and about the same as with A, F, FA and DA lenses). I'm frequently using the following K-Bajonet lenses:
Tokina SD 4.0/25-50
SMC Pentax-M 2.0/50
Helios 44K-4 (2.0/58)
Takumar 2.8/135 Bajonet
QuoteQuote:
support this forum by buying through a forum link.
aghosh1 is from the UK, so B&H / Adorama may not be the way to go.

05-20-2012, 05:29 PM   #24
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QuoteOriginally posted by RKKS08 Quote
aghosh1 is from the UK
My condolences to agosh.
05-20-2012, 05:40 PM   #25
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@ JimJohnson
If aghosh1 will neither use multiple flash arrangements nor do macro work with pTTL-capable flashes, he is much better off to skip pTTL and use plain old (and CHEAP) auto flashes. With (just an example) a Metz Mecablitz MZ40-2 (or -3...) and the correct SCA adapter he doesn't need to make any settings at all - just fire away, and every exposure as it should be. With m42 or K mount lenses, he just needs to set the same aperture at the flash as at the lens, with newer lenses ("A" setting or no aperture ring) nothing at all.

Last edited by RKKS08; 05-20-2012 at 07:17 PM.
05-21-2012, 08:53 AM   #26
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QuoteOriginally posted by selar Quote
I absolutely detest green button metering. Its clunky and its inaccurate. You're better off shooting in completely manual mode, change aperture and shutter speed at will, use a hand held meter or a metering app on your phone for the metering.
In what way? Green button metering still allows you to adjust aperture and shutter speed at will. it just greatly speeds the process of getting you to an initially reasonable value for shutter speed. It in no way limits or hampers you in any way whatsoever, and saves time and effort. there are no downsides whatsoever. Perhaps you weren't doing it correctly when you briefly experimented with it before writing it off?
05-21-2012, 03:31 PM   #27
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I got inconsistent exposure results. Something to do with the camera not being able to extrapolate the exposure from the wide open metering result, due to lack of information from the lens. I think it would be more useful if you could tell the camera which K or M lens you had mounted similar to manual input of focal length information.
05-21-2012, 04:06 PM   #28
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That doesn't make sense. No, the camera doesn't need to extrapolate exposure from wide open metering - that's the whole point of stop down metering. It measured te *actual* amount of light that will be received.

Now, in certain cameras with certain focus screens, stopping down a long ways may cause a bit of inaccuracy since they really weren't designed to function with the reduced amount of light. But that's going to be equally true of all methods of metering, not just Green button. And in any case, it's only true of certain cameras with certain focusing screens. My K200D with stock screen is perfectly consistent throughout the entire aperture range of all my manual lenses. Works like a charm.
05-21-2012, 06:02 PM   #29
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I had trouble in low light. And it was pretty much useless for action as well.
05-21-2012, 09:07 PM   #30
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Again, not sure what you were doing wrong, but there is mo difference between the metering performed by the Greem button versus other methods. And it's much faster to boot, so clearly more well suited to action than any other method.
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