Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
05-05-2018, 09:03 AM   #31
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,875
Original Poster
Ole

I think if you look at the greyscale value at F5.6 you will see if everything is based on this value all the graphs will fall on top of each other, or almost so

05-05-2018, 09:48 AM   #32
Pentaxian
swanlefitte's Avatar

Join Date: May 2015
Location: New Orleans
Photos: Gallery
Posts: 2,666
I have tried 3 more times with different surfaces at different distance. I also can point out I desaturated each image before taking a reading on the histogram. All tests performed on a tripod at 100 iso center metering wb set to daylight. There is a general trend but not much more than that. I think the amount of light and distance from camera play a big part in this combined with the camera deciding to jump up or down on readings in between. Looking though my camera settings dynamic range shadow corrections was set to auto if that might have some effect, I don't shoot jpg normally.
Thinking back to my A50 with modeling lights perhaps the flicker has some effect on metering? how much time does the camera meter for? Also with the a50 I had compared aperture priority in A setting to manual green button metering. On manual this necessitated I did not have the lens set to A because it would change the aperture as well as the shutter. I did use the A setting for Av mode.

Ks2 with M50 inside white room lit by outside cloulds at 1/3,1/2 sensitivity, grey concrete slab outside overcast, Rusted corrugated metal outside overcast, white washing machine outside overcast.
F2(85,85) 91,91,118
f2.8(100,105) 87,89,112
f3.5(105,105) 107,105,125
f4(125,125) 106,123,122
f4.5(130,140) 125,120,139
f5.6(140,140) 98,115,132
f6.7(140,140) 101,114,131
f8(145,130) 102,91,148
f9.5(140,135) 76,88,123
f11(135,130) 56,71,121
f13(130,125) 50,50,111
f16 (75,100) 44,44,82
f22 (100,100) 38,45,83
05-05-2018, 10:31 AM   #33
Lens Hoarder
Loyal Site Supporter
monochrome's Avatar

Join Date: Mar 2008
Location: St. Louis, MO
Photos: Gallery | Albums
Posts: 25,459
All: You’re certainly right on top of this

It is my 45th High School Reunion weekend. I’m pretty booked up this particular weekend (activities in 30 minute increments through tomorrow morning)!
05-05-2018, 10:43 AM   #34
Ole
Administrator
Ole's Avatar

Join Date: Sep 2006
Location: Copenhagen, Denmark
Photos: Gallery | Albums
Posts: 4,160
K-3 with M 50mm F1.7

Also with this lens are the two sets of exposures quite consistent except for the oddity af F16.

The exposure variation is easy to compensate for being basically constant from F4.8.

Figures in red are interpolated (no click stop at those apertures).

ISO was 100.





05-05-2018, 11:05 AM   #35
Ole
Administrator
Ole's Avatar

Join Date: Sep 2006
Location: Copenhagen, Denmark
Photos: Gallery | Albums
Posts: 4,160
QuoteOriginally posted by Lowell Goudge Quote
Ole

I think if you look at the greyscale value at F5.6 you will see if everything is based on this value all the graphs will fall on top of each other, or almost so
@Lowell Goudge

Good observation.

At least up to F19 if it wasn't for the odd man out, the K 50 F1.4 (I suspect my copy may have an unreliable aperture mechanism). Also the M28 sticks out some going a third of a stop above the rest.

05-06-2018, 01:52 AM   #36
Ole
Administrator
Ole's Avatar

Join Date: Sep 2006
Location: Copenhagen, Denmark
Photos: Gallery | Albums
Posts: 4,160
K-1 with K 50mm F1.4

Two sets of exposures are quite consistent.

The exposure variation is "prettier" than when the lens was used on the K-3.

Figures in red are interpolated (no click stop at those apertures).

ISO was 100.



05-06-2018, 02:26 AM   #37
Ole
Administrator
Ole's Avatar

Join Date: Sep 2006
Location: Copenhagen, Denmark
Photos: Gallery | Albums
Posts: 4,160
K-1 with M 50mm F1.7

Two sets of exposures are quite consistent except for an oddity at F3.5.

The exposure variation is quite flat and easy to compensate for.

Figures in red are interpolated (no click stop at those apertures).

ISO was 100.



05-06-2018, 02:33 AM   #38
Ole
Administrator
Ole's Avatar

Join Date: Sep 2006
Location: Copenhagen, Denmark
Photos: Gallery | Albums
Posts: 4,160
K-1 normalized at F5.6

K-1 with K 50mm F1.4 and M 50mm F1.7 normalized at F5.6



05-06-2018, 08:14 AM   #39
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,875
Original Poster
QuoteOriginally posted by Ole Quote
K-1 with K 50mm F1.4 and M 50mm F1.7 normalized at F5.6
any chance on posting the grey scale values too? i am trying to set up to make some averages etc.
05-06-2018, 08:18 AM   #40
Moderator
Not a Number's Avatar

Join Date: Mar 2012
Location: Venice, CA
Posts: 6,688
so why not put a shared spreadsheet on google docs and people can put the raw data points in there?
05-06-2018, 08:30 AM   #41
Ole
Administrator
Ole's Avatar

Join Date: Sep 2006
Location: Copenhagen, Denmark
Photos: Gallery | Albums
Posts: 4,160
QuoteOriginally posted by Lowell Goudge Quote
any chance on posting the grey scale values too? i am trying to set up to make some averages etc.
The gray scale values are in my previous posts for each individual lens/camera combo.

I can send you my spreadsheet if that would help. If so, PM me your mail address.
05-06-2018, 08:41 AM   #42
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,875
Original Poster
QuoteOriginally posted by swanlefitte Quote
I have tried 3 more times with different surfaces at different distance. I also can point out I desaturated each image before taking a reading on the histogram. All tests performed on a tripod at 100 iso center metering wb set to daylight. There is a general trend but not much more than that. I think the amount of light and distance from camera play a big part in this combined with the camera deciding to jump up or down on readings in between. Looking though my camera settings dynamic range shadow corrections was set to auto if that might have some effect, I don't shoot jpg normally.
Thinking back to my A50 with modeling lights perhaps the flicker has some effect on metering? how much time does the camera meter for? Also with the a50 I had compared aperture priority in A setting to manual green button metering. On manual this necessitated I did not have the lens set to A because it would change the aperture as well as the shutter. I did use the A setting for Av mode.

Ks2 with M50 inside white room lit by outside cloulds at 1/3,1/2 sensitivity, grey concrete slab outside overcast, Rusted corrugated metal outside overcast, white washing machine outside overcast.
F2(85,85) 91,91,118
f2.8(100,105) 87,89,112
f3.5(105,105) 107,105,125
f4(125,125) 106,123,122
f4.5(130,140) 125,120,139
f5.6(140,140) 98,115,132
f6.7(140,140) 101,114,131
f8(145,130) 102,91,148
f9.5(140,135) 76,88,123
f11(135,130) 56,71,121
f13(130,125) 50,50,111
f16 (75,100) 44,44,82
f22 (100,100) 38,45,83
Shadow correction realy messes things up. it grabs onto little highlights and low lights and shifts everything up to 2 stops

---------- Post added 05-06-2018 at 11:42 AM ----------

QuoteOriginally posted by Not a Number Quote
so why not put a shared spreadsheet on google docs and people can put the raw data points in there?
its possible looking into it
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!
aperture, bodies, button, camera, compensation, contrast, custom image, dslr, ev, exposure, gaps, greyscale, lens, lenses, matter, method, mode, photography, pm, post, results, sec, shadow, time, value, version
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Help requested - k-x wants to/can't work anymore, mirror jams? kroscha Repairs and Warranty Service 3 12-11-2017 01:56 PM
Nature Squirrel wants nuts, cat wants... photomax7 Post Your Photos! 3 09-24-2017 12:02 AM
Help ! Windows wants to update itself on my PC !! jpzk Digital Processing, Software, and Printing 36 11-01-2015 01:21 AM
Who wants to help smooth my Transition to Lightroom? Bonobo Digital Processing, Software, and Printing 20 03-02-2014 07:59 PM
Wife wants a 35mm Pentax advice help SnowWolf Pentax Film SLR Discussion 12 11-30-2007 05:48 PM



All times are GMT -7. The time now is 10:26 PM. | 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