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03-10-2019, 01:56 AM - 1 Like   #16
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QuoteOriginally posted by photoptimist Quote
What about this filter (ExpoDisc 2.0 Professional White Balance Filter - ExpoImaging, Inc.) that converts your camera into an ambient/incident light meter?
I have one of those threaded for 67mm (I used it with the K5 and K3). It doesn't work well because it is directional, and I never used it much due to having to screw it on and off the lens and its diameter also not matching the lens diameter. Using a stand alone light meter is easier, but require to carry a separate device.

---------- Post added 10-03-19 at 10:03 ----------

QuoteOriginally posted by zapp Quote
With digital sensors and instant histograms, the need for a light meter is even less prominent than 10 years ago.
Very true when the histogram has a bell shaped curve. Most (if not all) articles about exposure show nice bell shaped histogram and yes, when I have such nice histogram the automatic exposure of the camera works at its best.
Now, in practice, a lot of histograms have a U shape or even combinations of U shape and bell shape. With mixed U shaped histograms, the exposure to match average 18% gray is often shifted which require much post processing work to recover and loss of image quality.

---------- Post added 10-03-19 at 10:04 ----------

The idea of adding a ambient light meter on top of the camera would be to have the camera exposure automation to use TTL and ambient light metering to compute a better exposure.

03-10-2019, 08:08 AM - 1 Like   #17
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I guess I'd need to actually see this implemented to see how well it worked, but I'm imagining all sorts of problems that would require manual intervention. Like the exposure reading from the camera will change if I'm wearing a hat that shades the camera or not.

Something I'd like is a 'digital spotmeter'. After you take a photo you could move a little cursor around and get average values for say a 10x10 pixel area (this could be adjustable).
03-10-2019, 08:20 AM   #18
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The problem with an incident/ambient light meter on the top of the camera is that it won't be accurate when the photographer is near the camera especially if the camera is on a tripod at less than eye-height. The photographer's head and body will block most of the ambient light coming from behind the camera which is often the light that is illuminating the subject. And if the subject is in the sun or near some room lights (e.g., a studio) and the photographer is in the shade or at a different distance to the room lights, then the camera still needs to be carried over to the subject to get an accurate reading.

If incident/ambient light measurement is the goal, then there really is no substitute for holding one of those little white half-hemisphere meters right in front of the subject's face to get a correct reading because you want to measure light falling on the subject, not light falling on the camera.
03-10-2019, 10:03 AM - 1 Like   #19
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I'm certainly not suggesting that a built-in incident meter should be any camera's only metering method, but I do think that it would be useful often enough to be worth having as an option. In my imagination it would work like this:

You wouldn't want the camera to be constantly changing its settings based on the incident reading, because that's not how incident metering works. You only need to incident meter when the light changes, so I'd suggest that in incident mode the camera would only take a reading when you press the green button. Let's say you've got the camera in AV mode and set to incident metering -- you set the aperture and ISO you want, then you press the green button and the camera sets the shutter speed according to the incident reading. Then those values stay fixed until you decide to press the green button again to take another reading. TV and TAV modes would work similarly.

You wouldn't take the incident reading with the camera held to your eye. You'd use the camera exactly as if the camera itself was a handheld meter.

Of course there would still be times when I'd need to get my Sekonic out of the bag instead, but there would also be plenty of times when I'm shooting handheld (my normal style) that an incident meter built into the camera would suite me perfectly. I'd certainly like to have it as an add-on option that could clip into the hot shoe, communicate with the camera, and operate as I've described.

And it would be a unique selling proposition for Pentax.


Last edited by Dartmoor Dave; 03-10-2019 at 10:09 AM.
03-10-2019, 01:08 PM   #20
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QuoteOriginally posted by BrianR Quote
Like the exposure reading from the camera will change if I'm wearing a hat that shades the camera or not.
But that is precisely what happens now when you are not in LV.
Just tested the K1 now in case they had done something about this core failure of DSLR design.
Stood in a doorway pointing the camera inside in AV and the metering went from 1/30 to 1.2 sec depending on whether my thumb was over the viewfinder.
I doubt whether having an incident meter would be particularly useful in anything but M mode. It would be for those who put a bit of planning into the exposure rather than those who expect the camera to calculate it.
But as I said earlier the physical cost of it would be miniscule and the application of it would be firmware intended to run as an alternative of what the green button currently does.
03-13-2019, 04:19 PM   #21
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QuoteOriginally posted by GUB Quote
Stood in a doorway pointing the camera inside in AV and the metering went from 1/30 to 1.2 sec depending on whether my thumb was over the viewfinder.
This has been a known problem with SLR since in-camera metering was introduced. It is a question of physics. You to be able to see through the viewfinder means that light can travel the other way too. That is why they supply that little plastic viewfinder blind that we all lose.

If i am not holding the camera to my eye when taking a picture I always use Manual exposure mode and meter with the VF covered.
03-14-2019, 09:24 AM - 1 Like   #22
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I prefer having an external hand held meter. Would be too cumbersome to have it on camera. Also, I can use it with other cameras and mostly for shooting film. I own a digiflash. Absolutely versatile, tiny and lightweight.

03-14-2019, 11:29 AM   #23
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QuoteOriginally posted by biz-engineer Quote
Having a standalone light meter (Sekonic) that i use for metering with manual flash and also sometimes outdoors. Wouldn't it be a great idea that some next Pentax camera models would also feature an ambiant light meter, in addition to TTL metering in order to improve exposure settings?
All Pentax dSLRs feature a TTL ambient* light meter as a core feature for reflected light readings. What they do not support is a meter capable of incident readings. For those wishing such, an incident reading may be approximated using an 18% gray card or any number of diffusion domes made to fit over the lens front.

Addendum: It occurred to me that my pedantic comment might be taken as dismissive of the idea. It would be cool to have a hot-shoe mounted dome accessory or something similar.


Steve

(...has a hand-held meter with incident ability in the bag most of the time...comes in handy...)

* Ambient is a synonym of available light. Ambient light metering applies to both incident (light striking the subject) and "reflective" (illuminance from the subject) reading.


Last edited by stevebrot; 03-14-2019 at 12:01 PM. Reason: Added stuff
03-14-2019, 11:52 AM - 1 Like   #24
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QuoteOriginally posted by stevebrot Quote
All Pentax dSLRs feature a TTL ambient* light meter as a core feature for reflected light readings. What they do not support is a meter capable of incident readings. For those wishing such, an incident reading may be approximated using an 18% gray card or any number of diffusion domes made to fit over the lens front.

In situations where using my handheld incident meter isn't possible for reasons of social decorum, I often find myself using the old trick of approximating an incident reading by spot metering off the palm of my hand (plus half a stop to compensate for my skin tone). It's usually accurate enough to do the job, and almost always more accurate than an averaged reflected light reading from the scene. It's a trick you can get away with when incident meters, grey cards and the like just aren't appropriate. An incident meter built into the camera would be a big help too though.
03-14-2019, 12:00 PM - 1 Like   #25
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QuoteOriginally posted by Dartmoor Dave Quote
An incident meter built into the camera would be a big help too though.
Thanks for the reminder that it is not a bad idea. I have updated my comment.


Steve
03-14-2019, 12:14 PM   #26
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QuoteOriginally posted by GUB Quote
Just tested the K1 now in case they had done something about this core failure of DSLR design.
"Core failure" or known concern common to all TTL auto-exposure SLR cameras when used on-tripod or other than at the the user eye? Pentax makes note of the behavior in the user manual and has included a viewfinder shade in the box of every AE body it has sold since the ME Super. Other makers have provided a similar solution, with some opting for a viewfinder shutter rather than a slip-on shade.*

Read the manual and take appropriate precautions when shooting on tripod or with the camera held away from the eye.


Steve

* I have two such bodies...Ricoh XR-2s and Zenit Automat. FWIW, this concern was well known as early as the late 1960s with the release of the Konica Autoreflex T cameras and was addressed with a viewfinder shutter in the T3N model in 1975.

Last edited by stevebrot; 03-14-2019 at 12:39 PM.
03-14-2019, 01:01 PM   #27
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For sake of clarity regarding incident light metering, here are a few points:
  • It is important that the meter measure the light striking the intended subject as opposed to the light entering the lens
  • Ideally the above point is accomplished by standing near the subject with the meter oriented towards the expected position of the camera
  • For landscape work or photographing zoo animals, the above approach is not practical and potentially dangerous. If both camera and subject are lit by the same source, taking a reading backward from the camera is usually adequate.
  • Placing exposure with a spot reading may be a better and more precise alternative to taking an incident reading
  • A reflective light reading from an 18% gray card is a reasonable substitute
Incident readings are not a universal panacea, but are highly appropriate for many cases. For example:
  • Scenes where values might range from brightest white to almost black. Good examples might be sunlit alpine scenes (snow and rock and maybe even a few people), sunlit beaches, sky taking up much of the frame, and some architectural subjects.
  • Subject is shaded while the rest of the scene is not
  • Heavy backlighting (light source not in frame)
  • Whatever makes sense based on the rule of experience

Clearly, this is not a simple case of putting a lumisphere on the top of the camera as an alternative to TTL metering for general shooting.


Steve

(...generally uses an 18% gray card or incident reading for mountain film photography...an absolute godsend for that difficult subject...)

Last edited by stevebrot; 03-14-2019 at 01:27 PM. Reason: accuracy
03-14-2019, 01:37 PM - 1 Like   #28
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ambient light meter integrated into a camera is useless, you need to measure ambient (incident) light where your subject is, not where your camera is. even if you are out in the sun with your subject, what happens when you put on a baseball cap, or if you rotate your camera 90 degrees.

lets get practical here, it would never work, and then everyone would complain it is yet another useless option, installed simply because it could be.

if pentax is to add any additional light sensor, and i truly hope they are listening here, PLEASE add a sensor back for light reflected off the image sensor and give us back TTL flash as an option
03-14-2019, 10:51 PM   #29
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QuoteOriginally posted by stevebrot Quote
Incident readings are not a universal panacea, but are highly appropriate for many cases. For example: Scenes where values might range from brightest white to almost black. Good examples might be sunlit alpine scenes (snow and rock and maybe even a few people), sunlit beaches, sky taking up much of the frame, and some architectural subjects. Subject is shaded while the rest of the scene is not Heavy backlighting (light source not in frame) Whatever makes sense based on the rule of experience
Thanks for the clarification. Recently using the K1, I had some images underexposed 2 stops (this caught my attention, but I didn't find why). Yesterday I also noticed underexposure and I tried to understand, figured out that the Pentax K1 exposure is somehow affected by the most right of the RGB histogram components. For example, if the sky is a big area of the image, the histogram of the blue channel is closer to the right then the histograms of the green channels, so that the chrominance is preserved at the expense of the luminescence, while the main subject (not the sky) is underexposed, or at list not exposed as the eyes see it. Now if I do an auto-exposure in Silkypix, it re-adjusts brightness so that the luminescence histogram is centered. In both cases , the "exposure" is wrong. It would be good that a value of incident light value is recorded in the exif, as a third option.
03-15-2019, 02:37 AM   #30
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QuoteOriginally posted by stevebrot Quote
"Core failure" or known concern common to all TTL auto-exposure SLR cameras when used on-tripod or other than at the the user eye? Pentax makes note of the behavior in the user manual and has included a viewfinder shade in the box of every AE body it has sold since the ME Super. Other makers have provided a similar solution, with some opting for a viewfinder shutter rather than a slip-on shade.*

Read the manual and take appropriate precautions when shooting on tripod or with the camera held away from the eye.


Steve

* I have two such bodies...Ricoh XR-2s and Zenit Automat. FWIW, this concern was well known as early as the late 1960s with the release of the Konica Autoreflex T cameras and was addressed with a viewfinder shutter in the T3N model in 1975.
My words were"core failure of dslr design" and your comment shows that to be an appropriate term.. not only an issue with tripods also if your glasses hold your eye away and also if you pull back your head to find the green button
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