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07-16-2018, 11:29 AM   #16
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QuoteOriginally posted by Emirena Quote
Thanks for clearing up the EV vs EC confusion. I was trying to find more information on how to use and read the EV meter in different conditions but the manual is not so helpful. Screenshot helped. Green button just resets to defaults, correct? The insight that EC dial was oft. linked to film speed control on film SLRs makes a lot of sense.

I ended up shooting some daytime sailing photos in Av mode depending on whether I wanted to focus on subjects on my boat (1-10M distance) or distant ones. I used continuous shooting since there's so much action, but didn't try bracketing because the exposure looked decent with ISO 400-800 (and for fear of filling up my memory card). I did seem to very slightly underexpose most photos, but preferred not losing the cloud definition on the hazy, bright sky and horizon. It's tough to expose for dark water and harsh sunlight. Shadow compensation level 2 seemed to help reduce facial shadows on people. I just processed any RAW files (or double processed and photoshopped a composite) to retain exposure for both sky and people/boats.
One of the challenges to understanding metering and exposure is in realizing that the meter has no clue about the subject matter*. The meter can't tell that the camera is looking at a black cat on a black chair or a white rabbit on snow.

The meter merely measures the amount of light coming from the scene, makes the assumption that the scene is roughly 18% gray, and gives a meter reading or auto-exposure setting appropriate to reproducing an 18% gray image from the 18% gray scene. But if the objects in the scene are markedly darker or brighter than light gray, the meter will be wrong and the image will appear over-exposured or under-exposed respectively.

For example, a black cat on a black chair sitting in the sun may have the identical meter reading as a white rabbit on snow in the shade because both scenes have the same amount of light coming from them. And yet the black cat needs a much faster shutter or narrower aperture or lower ISO to create an accurately dark image of the dark scene. And the white rabbit needs a much slower shutter or wider aperture or higher ISO to create an accurately white image of the white scene.

So-called exposure compensation lets the photographer tell the meter that it's looking at a scene that differs markedly from 18% gray and that the meter reading needs to be compensated to create the correct exposure. That's the primary use of exposure compensation.

Some photographers also use exposure compensation to intentionally over-expose or under-expose the scene for artistic effects.

*P.S. Modern cameras are getting better and better at recognizing the scene and adjusting exposure accordingly. That actually makes using exposure compensation even harder because the photographer may not know whether the camera is already compensating for an excessively dark or bright scene.

07-16-2018, 12:13 PM   #17
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QuoteOriginally posted by Emirena Quote
Is there a flowchart or better explanation of the user interface for P-Line mode and program modes? It's not so intuitive. Does P mode retain exposure value as shutter speed or aperture are adjusted, too?
By P-Line mode, I am assuming you mean P mode on the mode dial. In P mode, the camera decides what combination of shutter speed and aperture work best for the amount of light metered at the current ISO. To the best of my knowledge, there is no detailed description of the actual program line(s) used in this mode and no mechanism on the K-70 to select a program line for a particular use case.* You can override the program line in P mode with your choice of aperture or shutter speed. In that case behavior is as if you are in Av or Tv mode. Pushing the "green" button will return settings to the program line.

If a specific programmed exposure behavior is desired, one the options for SCN mode may be appropriate, though again, those are not explained in any detail anywhere I am aware of. There is no way on the K-70 to stipulate a range of acceptable shutter speeds and/or a range of acceptable apertures with the ISO to vary as needed.


Steve

* I erred in my first comment by inferring that program line might be settable. While this is an option in higher-end models, such is not the case with the K-70. Likewise, the behavior of the auto-ISO feature on the K-70 also has only limited options for customization.
07-17-2018, 01:58 AM   #18
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QuoteOriginally posted by stevebrot Quote
I believe I understand him fairly well and while his complaint is a fine point, I agree. EV traditionally (say back 50+ years) refers to the open-ended numeric scale representing combinations of shutter speed and aperture that result in the same amount of light during exposure. Exposure is quite literally exposure. EV is unrelated to metering or film/sensor sensitivity.* Exposure compensation, OTOH, is a camera feature the user to transparently bias the meter for a series of over/under exposed images. The term "EV compensation" is inaccurate in that while the EV may be shifted, it is the exposure meter that is being compensated.
As most things EV is used for several purposes and in different context. One context for EV is in the above example you mention. Where it is used to describe an absolute value of exposure through equivalent exposure settings. Where EV1 is exposure settings of f/1.0 1/2s at ISO100 or other equivalent exposure settings.

EV is also used to describe relative difference in exposure, FI the difference between metered exposure and set exposure in manual mode, where the difference is showed on the EV bar on Pentax DSLRs.
Or when compensating exposure. +1 EV means "increase exposure one stop". It is in this context EV compensation and EC is used, and there is no real difference between them, except that EV compensation is by definition done by EV steps, whereas EC is not defined (but usually also done by setting EV steps).

QuoteQuote:
Yes, "EV compensation" is the term used in Pentax dSLR manuals since the *istD. I can't confirm for the *ist film camera, but I do believe that the manuals for all Pentax film bodies from the MZ series back to the ME use the term "Exposure compensation" as does the KMP Web site (all models including digital). Goggle "EV Compensation" and the results indicate the term being used in some tutorials and specifically in regards to Pentax and Nikon cameras. One tutorial even uses the term "EV exposure compensation"...go figure...
I believe I seen Sony mention "EV compensation" in their manuals too.

QuoteQuote:
Amazingly, the manual for the Pentax K2 uses "Exposure factor" to describe the dial used to bias its meter, a very appropriate term that avoids the traditional usage of EC and accurately describes the action of the setting...at least for automatic exposure mode.
"Exposure factor" was usable back when EC setting was on a linear scale where you could multiply the exposure factor with exposure settings (FI 4x 2x 1x 1/2x 1/4x). Nowadays the scale is logarithmic by the use of EV steps, so it is not a "factor" any more.
QuoteQuote:


Steve

* Early on, it became the norm with TTL bodies to define meter coupling (i.e. linear sensitivity range) in terms of EV with the meter set at ISO 100 with a fast normal lens attached. By extension EV100 came to commonly be used as an estimate of subject brightness for multiple purposes. In recent years there has been a move to use the term "Light Value" (LV) in preference to EV when used as a measure of brightness; LV being equivalent to EV100.

Last edited by Fogel70; 07-17-2018 at 02:34 AM.
07-17-2018, 02:41 PM   #19
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QuoteOriginally posted by Fogel70 Quote
"Exposure factor" was usable back when EC setting was on a linear scale where you could multiply the exposure factor with exposure settings (FI 4x 2x 1x 1/2x 1/4x). Nowadays the scale is logarithmic by the use of EV steps, so it is not a "factor" any more.
Thanks for the detailed explanation. I figured I would have to show a photo of the control ring on the K2 for it all to make sense. I don't know when exposure compensation was added as a feature to AE cameras. Konica was a pioneer in AE cameras and on at least one model (Autoreflex T) the advice was to temporarily change the shutter speed.

FWIW, both of my light meters provide EV readout as an alternative to shutter/aperture combination, the two being fully equivalent, of course even though neither is what the meter measured.


Steve

07-21-2018, 09:32 PM - 1 Like   #20
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The Pentax manuals (K-1 in particular) actually use both terms -- EV Compensation and exposure compensation -- in various places. The headings are usually "EV Compensation" but when describing the feature and/or the control button, they often use "exposure compensation".

I argue that neither EV compensation or exposure compensation are inaccurate. As described above by a couple people, the exposure is not being compensated for, it is in fact the meter's inaccuracy that needs compensation. But the term is not describing what is being compensated for, but instead the mechanism by which the compensation is provided; by an adjustment of the exposure (or the equivalent adjustment of the EV) used by the camera to take the picture.
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