Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
03-02-2018, 05:24 PM   #16
Pentaxian




Join Date: Dec 2016
Posts: 1,731
I've never used M42 lenses, but I do have M lenses. I do know they do not meter accurately on a DSLR like they do on a 35mm film body. I can put one on a very advanced AF model like the MZ-S and they meter fine. There is an exact variance at different apertures, and once I got used to this variance with a particular lens, I could simply adjust up or down by that amount as I set aperture. I use the green button method. Perhaps the DOF preview as meter indicator would be more accurate.

As to the meter reading in the VF, I don't have a K-30, but my K-S2 has a VF reading only given numerically- like +2 or -1 etc. while the LCD panel provides an actual metering graph. The premium camera models, however, like my K-5 IIs, also feature a graph in the VF, with + and - extremes and 0 in the center similar to your needle-in-center example, but more exact as there are markings to indicate the amount off from center.

03-02-2018, 06:21 PM   #17
Loyal Site Supporter
Loyal Site Supporter
UncleVanya's Avatar

Join Date: Jul 2014
Photos: Gallery | Albums
Posts: 15,230
QuoteOriginally posted by Not a Number Quote
There's usually a at least a half EV difference on my K10D between manual metering with an M42 lens in Av vs Green Button vs "Needle Match" (DOF preview metering). As stevebrot says, manual metering on the K10D isn't the greatest.



Only the bodies with a DOF preview position on the power switch (around the shutter button) have the "needle match" metering in manual mode with non-A lenses. These include M42, M and K series lesnes, and "A" lenses with aperture rings not set in the "A" mode.

Steve's comments were specific to Green button not needle match which is what I asked about but again it is odd that needle match would beat green button. Also I am pretty sure he wasn't just talking about the K10D but also the K-3. The point I am making is that Av mode with M42 is directly stopped down metering - as is Green Button. With M or A lenses not set to A the Green Button or optical depth of field is actually stopping down the lens rather than calculating a exposure from wide open - with M42 that's not the case - you set the lens to manual aperture and stop down while metering. In this case the methods that stop down should be more accurate than those that don't. What I can't grasp is why Green Button would beat Av with a lens that is already stopped down during exposure measurement and why match metering would be better than green button - since all of these are using the same basic method. The only advantage of match needle (optical preview) is that it is real time (as is Av) vs. a quick check moment in time. If scene lighting changes between measurements with green button then I can see inaccuracy creeping in.

Again - I'm not disputing results - I'm trying to fathom WHY they happen. It doesn't make any sense to me so far.
03-02-2018, 10:15 PM   #18
Site Supporter
Site Supporter
pres589's Avatar

Join Date: Jan 2014
Location: Lawrence, KS
Photos: Albums
Posts: 2,409
I think you nailed it, that the Green Button is grabbing light at a slice in time, vs. DoF Preview that is providing information on potentially much more time. This is why I prefer to use the DoF & "needle" method to Green Button.

It's kind of cool how Av mode on a DSLR works when an m42 lens is attached. It seems like sort of a hassle to use if not shooting at or near wide-open.
03-03-2018, 08:40 AM   #19
Moderator
Not a Number's Avatar

Join Date: Mar 2012
Location: Venice, CA
Posts: 6,053
QuoteOriginally posted by pres589 Quote
I think you nailed it, that the Green Button is grabbing light at a slice in time, vs. DoF Preview that is providing information on potentially much more time. This is why I prefer to use the DoF & "needle" method to Green Button.
Perhaps but tests on a diffused lit (not direct lighting) using a constant light source such as daylight on a bright cloudless day on a white painted interior wall will give different readings between the green button and needle match. The green button might give a shutter speed of 1/30th while the needle match gives 1/60th of a second (or it could be the other way around going from memory mind you). There are no trees outside my windows to vary the lighting from wind moving branches and leaves.

Edit: just did a quick test - it's raining outside, early morning so lighting is rather dim. Using my Takumar Super Multi Coated 50mm f/4 macro on the white interior wall at ISO 400 f/4 Av gives me 1/10th of a second while green button and needle match gives me 1/6th or 2/3rds of a stop difference.


Last edited by Not a Number; 03-03-2018 at 08:57 AM.
03-03-2018, 09:35 AM   #20
Site Supporter
Site Supporter
pres589's Avatar

Join Date: Jan 2014
Location: Lawrence, KS
Photos: Albums
Posts: 2,409
Not a lot of space between 1/10th and 1/6th. I think this might be a case where it's on the edge and the change looks drastic because it can't go to something between.

I'm glad that the DoF Preview gives me the needle match display and it's another reason why I want a higher end body instead of a K-70 or similar.
03-03-2018, 10:58 AM   #21
Loyal Site Supporter
Loyal Site Supporter
pschlute's Avatar

Join Date: Mar 2007
Location: Surrey, UK
Photos: Gallery
Posts: 3,172
My first Pentax DSLR was a *ist DS. Coming from film pentax cameras I was very happy that my old "K" and M lenses still worked and that the green button stop-down metering worked very well.

My second Pentax DSLR was a k10D. Excellent camera but it did not meter correctly with the old lenses. There was a progressive overexposure as I stopped down the lens and used green button metering. Some lenses worked better than others. This was put down at the time to the new type of focus screen developed by Pentax which transmitted more light through the viewfinder, but at the expense of metering with old lenses. The k20D suffered the same problems I believe.

Now i am using a K1 and so far it appears that green button metering with the old lenses is correct again.
03-03-2018, 12:48 PM   #22
Site Supporter
Site Supporter
landstrykere's Avatar

Join Date: Nov 2017
Location: Nittedal
Posts: 24
Original Poster
well, my K-30 is now brain dead after a botched firmware flash ( Bricked K-30 - PentaxForums.com ) and I bought this afternoon a second hand K-5 (13.500 shutter count).
Something that differs from the K-30: when in M mode, fixed iso, electronic level enabled, in the LiveView, exposure modification isn't shown at the same time that the shutter speed is modified (front dial). In the LiveView of the K-30, increase/decrease of shutter speed did translate into under/over exposition (liveview becoming darker/brighter). I may miss something in the manual, despite it's almost the same configuration tabs and menus (some more niceties in the K-5)
03-03-2018, 04:37 PM - 1 Like   #23
Loyal Site Supporter
Loyal Site Supporter
UncleVanya's Avatar

Join Date: Jul 2014
Photos: Gallery | Albums
Posts: 15,230
QuoteOriginally posted by landstrykere Quote
well, my K-30 is now brain dead after a botched firmware flash ( Bricked K-30 - PentaxForums.com ) and I bought this afternoon a second hand K-5 (13.500 shutter count).
Something that differs from the K-30: when in M mode, fixed iso, electronic level enabled, in the LiveView, exposure modification isn't shown at the same time that the shutter speed is modified (front dial). In the LiveView of the K-30, increase/decrease of shutter speed did translate into under/over exposition (liveview becoming darker/brighter). I may miss something in the manual, despite it's almost the same configuration tabs and menus (some more niceties in the K-5)
IF memory serves the K-30/K-50 liveview is more advanced than the K-5.

03-04-2018, 05:11 AM   #24
Site Supporter
Site Supporter
landstrykere's Avatar

Join Date: Nov 2017
Location: Nittedal
Posts: 24
Original Poster
QuoteOriginally posted by UncleVanya Quote
IF memory serves the K-30/K-50 liveview is more advanced than the K-5.
well, my K30 is resurrected (by booting in debug mode and reset), so I can now easily compare with the K5 bought yesterday, and yes, on the K30, in M mode with dumb lens, shutter speed modification up/down translates in darker/brighter visualization on the LV display.. Not on the K5. What a user on older thread named "exposure simulation" in the LV display : K-S2 Live View Exposure Simulation/Preview - PentaxForums.com
and Adam named that "full-time preview" in his comment:
K-S2 Live View Exposure Simulation/Preview - PentaxForums.com
and it seems that the K-S2 and the K3 (at least) do have that "full-time preview"/"exposure simulation". ("exposure simulation" is also can I read further, a Canon jargon)
On the K5, only EV compensation translates in the LV, but not shutter speed.
03-05-2018, 08:57 PM   #25
Otis Memorial Pentaxian
Loyal Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 33,190
QuoteOriginally posted by UncleVanya Quote
I don't understand why green button would be superior to Av.
It would take quite a bit of space to fully explain, but there is a method to the madness. Give it a try. It even works better in regular viewfinder mode that Av.


Steve
03-06-2018, 06:05 AM   #26
Loyal Site Supporter
Loyal Site Supporter
UncleVanya's Avatar

Join Date: Jul 2014
Photos: Gallery | Albums
Posts: 15,230
QuoteOriginally posted by stevebrot Quote
It would take quite a bit of space to fully explain, but there is a method to the madness. Give it a try. It even works better in regular viewfinder mode that Av.


Steve
I'm not fond of magical results, I prefer to know why... Lol. A character flaw perhaps but that's the truth.
03-08-2018, 07:22 PM - 1 Like   #27
Otis Memorial Pentaxian
Loyal Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 33,190
QuoteOriginally posted by UncleVanya Quote
I'm not fond of magical results, I prefer to know why... Lol. A character flaw perhaps but that's the truth.
I understand completely. To that end, I wrote up a summary post that skims the pertinent points, though there is probably still plenty of "magical thinking".

Stop-down metering, why it is a problem, and how to make it work - PentaxForums.com


Steve
03-11-2018, 08:34 AM   #28
Site Supporter
Site Supporter
landstrykere's Avatar

Join Date: Nov 2017
Location: Nittedal
Posts: 24
Original Poster
QuoteOriginally posted by stevebrot Quote
It would take quite a bit of space to fully explain, but there is a method to the madness. Give it a try. It even works better in regular viewfinder mode that Av.


Steve
QuoteOriginally posted by stevebrot Quote
I understand completely. To that end, I wrote up a summary post that skims the pertinent points, though there is probably still plenty of "magical thinking".

Stop-down metering, why it is a problem, and how to make it work - PentaxForums.com


Steve
interesting explanation.
And also I just found the green button way more natural and intuitive, the closest to manual shooting without any electronics in the way between the light and the film/sensor. While I keep playing with the K-5 and read forums, I have the feeling that many users of DSLR only, may have a "digitalized" thinking where "aperture" doesn't refer anymore to the diaphragm on the lense, or they presuppose that a lens communicates with the camera and if it does not it's a weirdness.
Until now the best with my M42s is: I set an ISO value, like on manual SLR (as much as possible I start always on ISO 100, push up if necessary), chose an aperture on the lens, do the light measurement and shutter setting with the green button, focus in viewfinder, occasionally adjust shutter or EV, shoot.

the whole autofocus and smart lens stuff feels weird to me, but then I shoot standing subjects, monuments, buildings, landscapes.

I found the focus screen shipping with the K-5 not so good, so I have put in a Canon Eg-S.

But now, I am wondering about the K lenses: to cut or not to cut the lever?
03-11-2018, 11:14 AM   #29
Otis Memorial Pentaxian
Loyal Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 33,190
QuoteOriginally posted by landstrykere Quote
But now, I am wondering about the K lenses: to cut or not to cut the lever?
There is no advantage to cutting the lever unless you are shooting Canon FF and need to clear the mirror. Keep the lever and you have automatic aperture actuation on Pentax dSLR and potential for resale to Pentax owners.


Steve
03-11-2018, 12:34 PM   #30
Moderator
Not a Number's Avatar

Join Date: Mar 2012
Location: Venice, CA
Posts: 6,053
Cutting the lever off will just allow you to stop down in Av mode. It would mean you would have to manual open and stop down the lens to focus and compose in Av, M green button, and M EV bar modes. You won't even have an A/M switch as you have on some screwmount lenses.

As well as lowering the resale value as noted before.
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!
button, camera, dslr, exposure, k10, k20, k30, k5, lcd, lenses, lenses exposure, live, m42, manual lenses, mode, models, photography, process, time, view, viewfinder
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Very very weird Pentax ME Super light meter readings, please help! Carlota_Nonnumquam Pentax Film SLR Discussion 7 03-18-2012 06:34 PM
Es 11 viewfinder readings in low light? pickles Pentax Film SLR Discussion 2 05-31-2011 05:07 AM
Light-readings off in full-manual marcdsgn Pentax DSLR Discussion 7 04-16-2009 04:38 AM
Power readings from the 200D fractal Pentax DSLR Discussion 6 01-26-2009 07:15 PM
Battery grip causing weird readings? Inspection Guy Pentax Camera and Field Accessories 3 02-02-2008 09:25 AM



All times are GMT -7. The time now is 11:57 AM. | See also: NikonForums.com, CanonForums.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