Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
11-02-2010, 03:11 PM   #16
Ira
Inactive Account




Join Date: Mar 2009
Location: Coral Springs, FL
Photos: Gallery | Albums
Posts: 5,218
QuoteOriginally posted by jolepp Quote
BTW ... why this shorting contacts business for CIF? I mean, is there some rational reason, or is this just a quirk?
The body has a bunch of contact points (look at it without a lens mounted), and older manual lenses don't. So when you mount the lens, the body contacts sit there like dead nipples, because the lens mount doesn't conduct electricity and communicate with the body.

By using aluminum tape, or tinfoil, you've brought those nipples to life, albeit by shorting them out (totally safe for the camera), and CIF works.

11-02-2010, 03:33 PM   #17
Inactive Account




Join Date: Dec 2008
Location: Ames, Iowa, USA
Photos: Albums
Posts: 2,965
QuoteOriginally posted by jolepp Quote
BTW ... why this shorting contacts business for CIF? I mean, is there some rational reason, or is this just a quirk?
At least it lets the camera know there's a lens mounted; it must also let the camera know it is a dumb lens (no doubt the camera tries to query the lens thru the Data pin - it will get no response from a dumb lens).

Only the Data Pin (the lowest one on the camera mount) need be shorted ... that must be the case because there are A lenses in non-A mode that have all other pins open.

You can test this by removing the lens and holding a bit of foil over the Data pin with your finger; the camera will behave just as if a lens is mounted.

Dave

Last edited by newarts; 11-02-2010 at 03:47 PM.
11-02-2010, 10:45 PM   #18
Veteran Member
jolepp's Avatar

Join Date: Oct 2010
Location: Finland
Photos: Albums
Posts: 3,196
Shorting out the data pin is a rational thing to do if you want CIF to work with a lens with non-conductive mount flange, but I was wondering why this works the way it does. This could provide the body with an indication of a lens being present, but if it was used for that purpose the the consistent thing to do would seem to be not to release the shutter at all.

OTOH, it seems that other aspects of the body behavior are modified as well depending on this: with green button metering it seems that unless the lens has a conductive base the body does not bother to try stop down the lens, also, it seems to raise the mirror during metering with conductive base lenses only. While the former kind of makes sense, the latter would seem to serve no purpose (?). A related quirk is stopping down during exposure in Av mode with conductive base lenses, while the exposure itself apparently is at fully open.

Usually, when I run into something that doesn't make sense like this it turns out I've misunderstood something. Understanding how something works under the hood usually helps to use it properly and/or to its full potential, so consider that my reason for wondering about these (in addition to plain curiosity ;-)
11-03-2010, 07:10 AM   #19
Inactive Account




Join Date: Dec 2008
Location: Ames, Iowa, USA
Photos: Albums
Posts: 2,965
QuoteOriginally posted by jolepp Quote
Shorting out the data pin is a rational thing to do if you want CIF to work with a lens with non-conductive mount flange, but I was wondering why this works the way it does. This could provide the body with an indication of a lens being present, but if it was used for that purpose the the consistent thing to do would seem to be not to release the shutter at all.
I don't understand; consistent with what? I presume that the consistent thing to do is to take a picture only when a lens is present.

QuoteQuote:
OTOH, it seems that other aspects of the body behavior are modified as well depending on this: with green button metering it seems that unless the lens has a conductive base the body does not bother to try stop down the lens,
I interpreted that as not bothering to do anything if no lens is mounted.

But my K-x does not try to close a conductive base manual lens to set exposure when the Green Button is pressed. I do not understand this - perhaps I don't have things set up correctly in some menu. It cannot set the exposure correctly if it doesn't close a non A lens' aperture when making the measurement!

QuoteQuote:
also, it seems to raise the mirror during metering with conductive base lenses only.... seem to serve no purpose
My K-x does not do this with conductive base M, adapted M42, or A lenses in non-A mode. In any event raising the mirror during metering would seem to be unnecessary.

QuoteQuote:
................ .................. A related quirk is stopping down during exposure in Av mode with conductive base lenses, while the exposure itself apparently is at fully open.
This happens when my K-x thinks a dumb A is mounted - but probably it only moves the lever to close the shutter to the aperture value chosen with the e-wheel - this would be the way I'd program it - move the lever to the electronically set position - the rest position for the camera's lever is far from its position for f1.2 for example, so you'd see considerable lever movement even when the algorithm was not actually trying to close the lens.

QuoteQuote:
Usually, when I run into something that doesn't make sense like this it turns out I've misunderstood something. Understanding how something works under the hood usually helps to use it properly and/or to its full potential, so consider that my reason for wondering about these (in addition to plain curiosity ;-)
Me too!

Dave

11-03-2010, 09:46 AM   #20
Veteran Member
jolepp's Avatar

Join Date: Oct 2010
Location: Finland
Photos: Albums
Posts: 3,196
QuoteOriginally posted by newarts Quote

I don't understand; consistent with what? I presume that the consistent thing to do is to take a picture only when a lens is present.
I meant consistent with not releasing the shutter when "enable use of aperture ring " is not set with an M-lens, or not releasing the shutter with an AF lens without focus lock.


QuoteQuote:

I interpreted that as not bothering to do anything if no lens is mounted.
It seems it is the same with no lens mounted as with one with a non conductive base mounted: the body doesn't operate the aperture lever in M-mode when the green button is pressed and the mirror stays put. Exposure time gets set though. (Tried this without a lens and kept an eye on the aperture lever counterpart of the body. Shorting the contact mentioned makes a difference, things work as if an M-lens was mounted. Also, the green button press with an M42 lens mounted produces no sound.)

QuoteQuote:
But my K-x does not try to close a conductive base manual lens to set exposure when the Green Button is pressed. I do not understand this - perhaps I don't have things set up correctly in some menu. It cannot set the exposure correctly if it doesn't close a non A lens' aperture when making the measurement!
The +/- should work the same with the k-x (in M-mode) as the green button does by default. There are two separate green button menu items that affect this (1.4 Green button = Green button & Action in M Mode = P LINE).

QuoteQuote:
My K-x does not do this with conductive base M, adapted M42, or A lenses in non-A mode. In any event raising the mirror during metering would seem to be unnecessary.
I see the mirror flip looking trough an M lens with fully open aperture as I press the green button. It is probably those two menu settings above?

QuoteQuote:
This happens when my K-x thinks a dumb A is mounted - but probably it only moves the lever to close the shutter to the aperture value chosen with the e-wheel - this would be the way I'd program it - move the lever to the electronically set position - the rest position for the camera's lever is far from its position for f1.2 for example, so you'd see considerable lever movement even when the algorithm was not actually trying to close the lens.
Again, looking trough an M-lens in Av mode when pressing the shutter I see the aperture to fully close if the ring is set that way. The result is the same exposure (as with fully open) provided that light doesn't change: it seems that the body closes the aperture either before of after the exposure for no reason.

Pretty mystifying:

Why raise the mirror with an M-lens?

Why not bother with that or trying to close the aperture with a non conductive base / no lens? (The simple thing to do would seem to be refusing to release the shutter or maybe treat these the same way?)

Why the aperture operation with an M-lens in Av mode?

Last edited by jolepp; 11-03-2010 at 09:47 AM. Reason: quote fix
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
focus, focus lens, k-mount, lens, pentax lens, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Can a manual-focus lens have back focus problems? PocketPixels Pentax DSLR Discussion 33 02-13-2011 05:37 AM
Manual Focus lens Bramela Pentax SLR Lens Discussion 26 05-02-2010 05:56 PM
Front focus/ back focus on Manual lens. Possible? WangJianWei Troubleshooting and Beginner Help 6 04-20-2009 07:50 PM
manual lens focus question kjfaust Pentax DSLR Discussion 11 05-16-2008 05:20 PM
Manual focus lens Charles Pentax SLR Lens Discussion 1 01-28-2007 03:14 PM



All times are GMT -7. The time now is 12:27 PM. | See also: NikonForums.com, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top