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04-03-2019, 10:42 AM   #16
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QuoteOriginally posted by dms Quote
Ultimately it is about understanding exposure theory, and studying this will give huge benefits down the road. I really like "Exposure Manual," 3rd ed., 1974, by Dunn and Wakefield. Also Ansel Adams "Camera and Lens" (although we don't expliciely use his zone system, the way of looking at a scene in terms of zones is still valid/useful). They both [Dunn and Adams] discuss exposure meters (incident, spot, averaging) but that is less important than exposure in terms of mid tones and balance of light to dark areas.
I agree. The ranges of values within the frame is often large enough that placement of exposure on the intended subject is often required with special techniques (HDR or, with film, compensating development) being applied if needed. A good book is of immense value. I learned the basics from a paperback pamphlet in the late 1960s lent me by a friend and and came to more complete knowledge courtesy of Ansel Adams, "The Negative" in the early 1980s. While some may disagree, my experience has been that the principles of light measurement and exposure remain the same with digital sensors as with film. While I strongly suggest Adams' "The Negative" (I recommend the early 80s editions in gray cover, printed while the master was still alive.), I suspect that a good public or college library might have several useful and complete books on the subject.


Steve


Last edited by stevebrot; 04-03-2019 at 01:56 PM.
04-03-2019, 10:46 AM   #17
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QuoteOriginally posted by gofour3 Quote
I found them in an old Pentax book that I have:

"How to select & use Pentax SLR Cameras" (Carl Shipman) published in 1977.

It has diagrams for M42, K & M series bodies.

Phil.
I found one of your old posts with scans!

Pentax's MF SLR Metering Pattern: Just Centerweighted? - Page 2 - PentaxForums.com


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04-03-2019, 10:48 AM - 1 Like   #18
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Good article pertinent to Pentax dSLR metering in particular...

Camera metering modes explained


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04-03-2019, 11:12 AM   #19
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QuoteOriginally posted by stevebrot Quote
I found one of your old posts with scans!
Yep that's the book, has many other camera patterns as well.

Phil.

04-03-2019, 11:59 AM   #20
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QuoteOriginally posted by dms Quote
....
Ultimately it is about understanding exposure theory, and studying this will give huge benefits down the road. I really like "Exposure Manual," 3rd ed., 1974, by Dunn and Wakefield. Also Ansel Adams "Camera and Lens" (although we don't expliciely use his zone system, the way of looking at a scene in terms of zones is still valid/useful). They both [Dunn and Adams] discuss exposure meters (incident, spot, averaging) but that is less important than exposure in terms of mid tones and balance of light to dark areas.

These older books tend to also treat (practical) exposure theory, as opposed to (only/largely) saying use matrix here and use spot here, and so on. I have no idea if there are good current books on the subject--the few I have looked at are about mechanics and not practical exposure theory.

.....
The Adams series should be recommended reading for all serious photographers. There have been a number of recent books on exposure theory and practice written by several authors. Some good some not so. Books have been written about how to apply the Zone system to digital acquisition that may be of interest.

A few with my personal impressions:
Optimum Digital Exposure -Bob DiNatale. Goes pretty deep into the subject of getting the most from sensors.

Here Are a Handful of Digital Exposure Axioms:
> The “METERED” exposure and the “OPTIMUM” exposure… Can Never The Same!
> The “METERED” exposure and the “PROPER” exposure are… Only The Same When Metering A Gray Card.”
> The “OPTIMUM” exposure… Produces Maximum Detail in the Shadows.”
> There is… only one “OPTIMUM Exposure” for any given scene.”
…The “OPTIMUM” exposure is… the exposure that will place the brightest part of the scene at 99+% in your software.

LuLa – OneZone


George Jardine
. Interesting but you need to buy into the series to learn more - I have not bothered!

Revisiting The Zone System… or, How I Learned To Love My Light Meter Again.


Mastering Exposure and the Zone System for Digital Photographers - Lee Varis. An interesting and practical introduction to adapting some Zone system practice to digital. However there are one or two errors (from memory) with the understanding of LR and ACR

amazon.com: Mastering Exposure and the Zone System for Digital Photographers (9781598639872): Lee Varis: Books?tag=pentaxforums-20&

Finally a real recommendation for Common sense and real world stuff about digital exposure. Read the articles by Iliah Borg and Alexy Danilchenko. RawDigger and FastRaw viewer Iliah Borgs baby.

And - the work of Norman Koren

Last edited by TonyW; 04-03-2019 at 12:26 PM.
04-03-2019, 01:05 PM   #21
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QuoteOriginally posted by TonyW Quote
And - the work of Norman Koren
To quote Koren, "...exposure meters are dumb, really dumb..."
Norman Koren | A simplified zone system for making good exposures
Using a simplified variation on Ansel Adams' famous Zone System to ensure maximum information and maximum control in post processing.
His pages and tutorials are getting a little long in the tooth, but still worth spending time with. BTW, for those with whom the name does not ring a bell, perhaps they may have heard of the Imatest products for lens/sensor performance? Koren is the creator of Imatest.


Steve

Last edited by stevebrot; 04-03-2019 at 02:00 PM.
04-03-2019, 01:49 PM   #22
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QuoteOriginally posted by stevebrot Quote
To quote Koren, "...exposure meters are dumb, really dumb..."
:-) Absolutely, and once that is understood by photographers it will also be understood that exposure meters do not make mistakes, however photographers do.

Yep, familiar with his Imatest work
04-03-2019, 04:17 PM - 1 Like   #23
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QuoteOriginally posted by BruceBanner Quote
I understand what the metering system does, but I always just stay in Matrix and deliberately under or over expose using the EV compensation (in Av mode that is). It occurred to me the other day that even when you have some dynamic lighting in your frame and say you want to protect that bright part from having it's highlights blown out (and are content with the rest being plunged into dark shadows), you could set to spot and take the shot, or just stay in matrix and keep underexposing till the bright part is protected. I tried doing this and the results looked the same, no difference with that particular example. In fact... spot was worse because you need to have that bright part of the image central in the frame, for those instances where the bright part in a dynamic scene is off centre then spot won't help you, matrix with ev comp will.

So I've always just stayed in Matrix and adjusted my exposure via EV compensation. My question is, are both routes pretty much the same end result, or is there something quite critically different I'm missing?
  • With metering choices, the exposure is kinda more 'automatic', however you do have a little more work to do in terms of changing the metering method, framing the shot (relevant to the method, such as centre for spot), possibly locking exposure and then recomposing for the shot.
  • EV Compensation requires no reframing or AE-L per se, but you might have to chimp more till you get the right exposure for the part of the image you want to protect (conversely happy to ruin/let go of the other dynamic range etc).


I know, sounds silly to compare the two, but really.. I hardly ever toggle out of matrix and just wondered if there was something else missing than I can't get from my constant EV Compensation use. I mean I do occasionally toggle to spot for those kinda events that it's really important (public speaking, concerts) where I just want the singers/speakers head exposed well and to hell with the surroundings etc, but yeh...


TIA!

Bruce
if you are going to use spot metering in place of EV compensation and matrix metering, then you likely should either shoot in manual mode with green button metering, or use the exposure lock function in what ever auto exposure mode you are using (Av Tv or Tav mode) by either of these actions you can meter first, then reframe the shot as you want for composition, I am no sure with today's cameras, but in the days before digital, centre weighted metering in many cameras was biased to the lower portion of the horizontal frame because of the premise that the sky was always bright, there were tests done with off centre lights and both left and right rotated vertical formats that gave different results.

The fundamental idea of EV compensation is somewhat more related to the need to deliberately under / over expose a whole series, for example when shooting either low key or high key shots, or when shooting in snow where the whole thing will be dull grey when you don't, or in the slide film days when you under exposed by 1/3 to 1/2 stop to increase color saturation, when using bodies that had DX encoded film cartridge readers, and you wanted to force the exposure compensation, or deliberately push process B&W film,

Before DX encoding you simply set the ISO differently, most people for example shot Kodachrome 64 at ISO 80, effectively under exposing by 1/3 stop, or shot 400ISO B&W film at anything from 800 to 3200 ISO and then compensated by extending developing time to get correct density on the negative, but really grainy shots

I trust this helps

04-03-2019, 05:55 PM - 1 Like   #24
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QuoteOriginally posted by stevebrot Quote
Good article pertinent to Pentax dSLR metering in particular...
That article is a bit out of date. With the new 86k RGB metering sensor, metering can be way more intelligent and granular than the old 77 segments mentioned in the article.



The 86k metering sensor has 1350 metering segments made up of three striped [RGB] 45x30 arrays (plus 1350 segments used for flash exposure).

The coverage looks like this on a K-1:


and this GIF animation illustrates the useful scene detail the metering data is able to capture across each of the RGB arrays:



Plus the article lacks mention of handy AE options like 'Link AE and AF point', which will actively steer the AE to the active focus point. New WB options enabled by the 86k RGB metering sensor like 'Multi-Auto White Balance' also deserve a mention and illustrate some of the exposure smarts enabled by the better metering sensor.
04-03-2019, 07:25 PM   #25
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Great thread, thanks. Just changed mine from center-weight to matrix after reading the pros and cons.
04-04-2019, 02:16 AM   #26
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Wow, ok... so heaps of responses here, cool, looks like I'll be reading a lot of these more thoroughly and exploring more over the weekend.

I wasn't really trying to get into matters of 'exposure' per se, or rather 'optimal' etc, because (and perhaps I am being naive here) I was kinda under the impression that there is no such thing as 'the right exposure' for any given shot, that is up to the user to decide how to manage the exposure (decide on a well balanced shot or deliberate high/low key image etc).

I was simply wondering if for any given scene, you can end up at the desired chosen exposure that the user wants to do the shot at with any metering mode (and through the use of EV compensation). For example, right now, i sat my camera on the table and used manual mode, matrix metering and green buttoned to give a x shutter speed that put me at '0' EV. I then shifted to Spot meter and did the same (green button) and it now gave me an EV of +1 equivalent should I have been in Matrix, so if I went back to Matrix and shifted my EV up to +1 (through shutter speed adjustment) it was exposing exactly the same as when green buttoned off Spot.
So my point is, these are all just different paths to get you to the same point, correct? I understand that green buttoning in each different metering mode will result in different shutter speeds etc, I get all that, I was just curious if for example I was in Av mode, fixed ISO, and I used Matrix mode and I adjusted EV Comp to either +5 or -5 and somehow IT COULD NOT MATCH an exposure given in Centre or Spot (that also was using EV to the same extremes)? Does that make sense? lol prolly not.
04-04-2019, 02:44 AM - 1 Like   #27
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QuoteOriginally posted by BruceBanner Quote
IT COULD NOT MATCH an exposure given in Centre or Spot (that also was using EV to the same extremes)?
Well, Spot only measures a small 'patch' that's probably about 2% of the frame, and ignores the other 98% of scene lighting and colours. So that's all that you'd be working with. Lots of room for variation in your metering results when using Spot.

For what it's worth, the K-5 manual illustrates the differences between Centre-weighted and Spot quite well:


Works much the same in K-1/ KP.

Last edited by rawr; 04-04-2019 at 02:59 AM.
04-04-2019, 03:09 AM   #28
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I'm comfortable with centre weighted. This has got me thinking to experiment with the matrix metering again.
04-04-2019, 07:48 AM   #29
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QuoteOriginally posted by BruceBanner Quote
.... I was kinda under the impression that there is no such thing as 'the right exposure' for any given shot, that is up to the user to decide how to manage the exposure (decide on a well balanced shot or deliberate high/low key image etc).
It is quite true that you can generally point and shoot and let the camera get on with it and produce a nice acceptable result - most of the time. 'Correct or right exposure' may also be debateble as we can make many corrections in post but you may wish to consider the concept of optimal exposure. Broadly this applies equally to digital or analogue acquisition. It is generally considered good practice to aim to expose to utilise all of your sensors dynamic range without clipping important highlights. Depending on the scene DR and your requirements optimal exposure will place your data to the right hand edge of the histogram. Doing this you will have optimised your exposure which means you have kept as much DR as possible and avoided noise characteristics in the shadows allowing greater control in post. This assumes that the scene DR you wish to capture falls within the senors DR capablity. You may have 8 - 12 stops DR depending on your system - underexposure will loose shadow detail by loosing DR and placing values lower than necessary in the 'noise' areas of your capture.

Be aware your raw editor of choice will probably lie to you and in many cases suggest that you are overexposing when in fact you could be up to a couple of stops below sensor capacity. Resulting in loss of camera DR and potential noisy shadows, should you take the initial rendering as gospel

All bets are off however should the scene DR exceed sensor capacity. In these cases you will need to make a choice of either sacrificing some highlight or shadow detail, or adding light to the scene or consider multiple exposures or HDR.

QuoteQuote:
I was simply wondering if for any given scene, you can end up at the desired chosen exposure that the user wants to do the shot at with any metering mode (and through the use of EV compensation). For example, right now, i sat my camera on the table and used manual mode, matrix metering and green buttoned to give a x shutter speed that put me at '0' EV. I then shifted to Spot meter and did the same (green button) and it now gave me an EV of +1 equivalent should I have been in Matrix, so if I went back to Matrix and shifted my EV up to +1 (through shutter speed adjustment) it was exposing exactly the same as when green buttoned off Spot.
IF you point your camera at a single tone e.g. plain wall in any colour and shade switching to spot, centre or matrix should yield the same exposure figures and if you actually expose and examine the histogram I suspect you will see the same spike in the same position. My guess is that position will be left of centre indicative of a system calibration point of around 12%

Now if you point your camera at a 'normal' subject you will find that the metering modes likely disagree.

Spot reading will only be 'correct' (not necessarily Optimal!) for a subject with a 12% grey value (filling the spot circle) - a Kodak 18% grey card will need exposure increase of around 1/2 stop or positioning 45 degrees from light source.

Matrix will adjust that exposure to what the preset algorithms decide about all the collected data collected and may even make a 'safety' allowance if there are enough bright areas in the frame of underexposing slightly to protect from clipping - but who knows as these things are generally not fully documented by the manufacturer. As an aside I understand that Nikon (sorry!) matrix seems to consistently underexpose by 2/3 stop in an effort to prevent clipping - sorry not sure what Pentax generally does under similar circumstances

Centre Weighted will also adjust exposure based on its particular pattern and what is under the main area of that pattern.

All may need your input for adjustment based on the ROI to achieve optimal exposure. Depending on subject matter all may achieve an 'acceptable' image without input and one that will respond well to post work.

QuoteQuote:
So my point is, these are all just different paths to get you to the same point, correct?
Correct

Last edited by TonyW; 04-04-2019 at 07:58 AM.
04-04-2019, 08:40 AM   #30
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QuoteOriginally posted by BruceBanner Quote
I was simply wondering if for any given scene, you can end up at the desired chosen exposure that the user wants to do the shot at with any metering mode (and through the use of EV compensation).
???

Metering mode and chosen exposure are mutually exclusive. Assuming a Pentax dSLR; yes, one can bias exposure freely using EC and/or M mode with any of the three supported metering modes.


Steve
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