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Forum: Photographic Technique
04-04-2019, 01:38 PM
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But wait! There's more!
Taking the example from my previous post...
 Quote: - One spot meters a homogeneous portion of a scene and determines that they want to place exposure at that part of the frame five stops lower than the metered EV reading. (For zonies, that would be zone 0...black.) Using ether EV comp or M mode, they attain the desired -5 stops from the spot meter reading.
- Taking the photo, they are gratified to see that the area they placed exposure to is indeed black.
- Remembering the desired EV from photo above and with the camera still on the tripod, untouched, they change to matrix metering and note that the meter indicates two stops less exposure than the spot meter reading. Knowing the desired EV from before, they use EV comp and/or M mode to set the camera to -3 EV from the first exposure.
- Taking the photo, they are gratified to see that it is identical to the first.
Instead of changing the camera settings in step #3, the photographer accepts the metered EV and sets the camera to it, makes their exposure and applies three stops less "exposure" to the imported DNG in Lightroom. Would one still expect to two photos to be the same?
Steve
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Forum: Photographic Technique
04-04-2019, 01:22 PM
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We have a disconnect somewhere.
OK...perhaps a specific example might help:- One spot meters a homogeneous portion of a scene and determines that they want to place exposure at that part of the frame five stops lower than the metered EV reading. (For zonies, that would be zone 0...black.) Using ether EV comp or M mode, they attain the desired -5 stops from the spot meter reading.
- Taking the photo, they are gratified to see that the area they placed exposure to is indeed black.
- Remembering the desired EV from photo above and with the camera still on the tripod, untouched, they change to matrix metering and note that the meter indicates two stops less exposure than the spot meter reading. Knowing the desired EV from before, they use EV comp and/or M mode to set the camera to -3 EV from the first exposure.
- Taking the photo, they are gratified to see that it is identical to the first.
Doing something similar, but with the matrix reading and exposure done first would be equally possible, but without the option of knowing ahead of time how to get black for the desired portion of the frame.
Note that the initial readings for both meter modes may be deemed quite accurate even though they provided different numbers, though a master photographer looking on might ask why one would use matrix metering if they wanted to place exposure.
Steve
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Forum: Photographic Technique
04-04-2019, 12:52 PM
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Ummmm...that is ten stops on a camera that only supports 14.
We have a disconnect somewhere.
Steve
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Forum: Photographic Technique
04-04-2019, 08:53 AM
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Define "COULD NOT MATCH".
If you mean the same EV (not the same as EV comp), that is easily done in M mode. If the center of your scene is much brighter or darker than the rest of the screen and you are using exposure automation, you will be limited to the amount of EV comp supported by your camera.
Don't confuse metering with exposure or exposure automation. Metering provides a suggested exposure value (EV) consistent with the meter being used. Exposure is the amount of light permitted to strike the sensor (expressed as EV). Exposure automation allows the camera to follow a meter's suggestion for EV.
Steve
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Forum: Photographic Technique
04-04-2019, 08:40 AM
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???
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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Forum: Photographic Technique
04-03-2019, 01:05 PM
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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
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Forum: Photographic Technique
04-03-2019, 10:48 AM
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Forum: Photographic Technique
04-03-2019, 10:46 AM
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Forum: Photographic Technique
04-03-2019, 10:42 AM
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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
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Forum: Photographic Technique
04-03-2019, 10:23 AM
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Cool! I found this diagram in a post by PF user @Cuthbert from several years ago.
Steve
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Forum: Photographic Technique
04-03-2019, 10:05 AM
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Indeed! May I ask where you got meter pattern diagrams for your cameras?
Back in the ancient days, camera reviews would often include a diagram showing the the meter sensitivity pattern so that a buyer might be aware prior to purchase. Usually, this would not be an issue, but on some cameras, the weighting to avoid sky brightness would be abrupt enough to cause problems when doing a vertical composition. My late-1960s vintage Minolta SR-T 101 avoids this with its excellent CLC metering system which evaluates scene contrast as well as brightness using a primitive form of matrix metering (only two cells!). It works amazingly well.
Steve
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Forum: Photographic Technique
04-03-2019, 08:20 AM
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No...EV compensation is applied to the set exposure and is not related to metering. Proof? It works with arbitrary values set manually.
In regards to the metering itself, the difference between the three types is as follows:- Spot only evaluates the area within a circle of limited circumference. Usually, this means the center of the frame unless set somewhere else.
- Center-weighted averaging evaluates the full frame, but weighted to the center, often with reduced sensitivity in the upper portion of the frame (landscape orientation). This type was dominant before the advent of evaluative matrix metering.
- Evaluative matrix takes measurements from multiple areas of the frame, evaluates those values and uses the results to provide a reading to the camera. This form is most prevalent in modern cameras.
All three types are capable of being fooled, with matrix being the most robust when confronted with difficult light. Center-weighted is quite capable, despite being very simple from a technical perspective. Spot metering is a specialized tool and should not be used unless the operator knows exactly what they are wanting to do with the reading (hint: requires either M-mode or EV comp).
All of this having been stated, the statement below remains a strong maxim:"There is no such thing as an accurate or correct meter reading as it applies to exposure." Yes, a meter may be properly calibrated and yes, it may be backed by sophisticated algorithms, but for most subjects the meter reading is at best a blunt hint to the photographer/camera as to how much light to admit to the film or sensor. All the meter does is give its best estimate of a middle value that MIGHT provide usable exposure for all elements in the frame.
Steve
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