2017 PF T-shirts are Now on Sale!

icy · 12-09-2011, 07:55 AM

Hi,

I am using a Helios 44m-4 with Pentax K-r. I notice that when I switch to Av mode, the output image is darker than image captured in M-mode (as you can see in the first image below). The expect result is as in the 2nd image, which is taken with M-mode (green button is pressed to measure the light source.)

My question is: Why does the Av-mode report wrong light parameter? Am I using Av mode in wrong way? Does the Av mode work with Helios lens?

Thank you very much.

Demo:

The first image: f/2.8, 1/45s, Av mode, link = http://vonhudieu.net/zen/picture.php?/381/category/18
The second image: f/2.8, 1/15s, M mode (green button pressed to measure light source.), link = http://vonhudieu.net/zen/picture.php?/382/category/18

bobpur · 12-09-2011, 08:36 AM - **1 Like**

Hi

Un documented rule, when using M42 screw mount manual aperture lenses that do not have a clean metal mount
that grounds out the contacts" add +1.7 ev
Forget that Green button thing it just adds to your shutter count and makes you do 2 steps for each Pic !
Pentax should have had a metering on the half press shutter button or proper metering in Av mode,
My Sony A33 works with any lens and meters without the stopdown thing

Philoslothical · 12-09-2011, 08:37 AM - **1 Like**

Hi icy, as I mentioned in your last thread, you need to use old m42 lenses in M mode with green button metering to get a proper exposure. The camera has no way of knowing what aperture you're using with these lenses, so it makes the best guess it can on exposure, but it is not accurate.

Originally posted by bobpur

Forget that Green button thing it just adds to your shutter count and makes you do 2 steps for each Pic !

What on Earth are you talking about? The shutter doesn't fire when metering with the green button. That's just bad info.

jezza323 · 12-09-2011, 01:08 PM

Originally posted by Philoslothical

What on Earth are you talking about? The shutter doesn't fire when metering with the green button. That's just bad info.

the rest of the info is pretty accurate in my experience, but yeah not the green button bit!

icy · 12-09-2011, 05:27 PM

Originally posted by Philoslothical

Hi icy, as I mentioned in your last thread, you need to use old m42 lenses in M mode with green button metering to get a proper exposure. The camera has no way of knowing what aperture you're using with these lenses, so it makes the best guess it can on exposure, but it is not accurate.

Oh I see it now

Thank you very much!

**eddie1960** · 12-09-2011, 05:54 PM

well question has been answered.
but
holy smoke that tak looks like it's been through several war zones

how's it performing

12-09-2011, 07:55 AM	#1
icy Senior Member Join Date: Jun 2011 Location: Sài Gòn city, Việt Nam Photos: Gallery \| Albums Posts: 185	Pentax K-r and Helios 44m-4: Av mode doesn't work? Hi, I am using a Helios 44m-4 with Pentax K-r. I notice that when I switch to Av mode, the output image is darker than image captured in M-mode (as you can see in the first image below). The expect result is as in the 2nd image, which is taken with M-mode (green button is pressed to measure the light source.) My question is: Why does the Av-mode report wrong light parameter? Am I using Av mode in wrong way? Does the Av mode work with Helios lens? Thank you very much. Demo: The first image: f/2.8, 1/45s, Av mode, link = http://vonhudieu.net/zen/picture.php?/381/category/18 The second image: f/2.8, 1/15s, M mode (green button pressed to measure light source.), link = http://vonhudieu.net/zen/picture.php?/382/category/18

Thread Tools	Search this Thread
Show Printable Version E-mail to a Friend	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Sibling Rivalry: Helios 44M vs. Helios 44M-4	stevebrot	Pentax SLR Lens Discussion	36	08-03-2013 09:31 AM
Can I use a Helios 44m on K-r?	Eric_the_fish	Pentax K-r	11	12-08-2011 03:02 AM
Helios 44M-4 needs your help...	sushamyraj	Pentax SLR Lens Discussion	8	10-02-2011 12:45 PM
Helios 44M-4 vs 44M	teartear	Pentax SLR Lens Discussion	27	08-24-2011 03:25 AM

12-09-2011, 08:36 AM - 1 Like	#2
bobpur Inactive Account Join Date: Jul 2010 Photos: Gallery Posts: 328	Hi Un documented rule, when using M42 screw mount manual aperture lenses that do not have a clean metal mount that grounds out the contacts" add +1.7 ev Forget that Green button thing it just adds to your shutter count and makes you do 2 steps for each Pic ! Pentax should have had a metering on the half press shutter button or proper metering in Av mode, My Sony A33 works with any lens and meters without the stopdown thing

12-09-2011, 08:37 AM - 1 Like	#3
Philoslothical Veteran Member Join Date: May 2011 Posts: 1,723	Hi icy, as I mentioned in your last thread, you need to use old m42 lenses in M mode with green button metering to get a proper exposure. The camera has no way of knowing what aperture you're using with these lenses, so it makes the best guess it can on exposure, but it is not accurate. Originally posted by bobpur Forget that Green button thing it just adds to your shutter count and makes you do 2 steps for each Pic ! What on Earth are you talking about? The shutter doesn't fire when metering with the green button. That's just bad info.

12-09-2011, 01:08 PM	#4
jezza323 Veteran Member Join Date: Jan 2009 Location: Brisbane Photos: Gallery Posts: 1,421	Originally posted by Philoslothical What on Earth are you talking about? The shutter doesn't fire when metering with the green button. That's just bad info. the rest of the info is pretty accurate in my experience, but yeah not the green button bit!

12-09-2011, 05:27 PM	#5
icy Senior Member Join Date: Jun 2011 Location: Sài Gòn city, Việt Nam Photos: Gallery \| Albums Posts: 185 Original Poster	Originally posted by Philoslothical Hi icy, as I mentioned in your last thread, you need to use old m42 lenses in M mode with green button metering to get a proper exposure. The camera has no way of knowing what aperture you're using with these lenses, so it makes the best guess it can on exposure, but it is not accurate. Oh I see it now Thank you very much!

12-09-2011, 05:54 PM	#6
eddie1960 Loyal Site Supporter Join Date: Aug 2010 Location: Toronto Photos: Gallery \| Albums Posts: 12,271	well question has been answered. but holy smoke that tak looks like it's been through several war zones how's it performing

Pentax K-r and Helios 44m-4: Av mode doesn't work?

2017 PF T-shirts are Now on Sale!