Question re: P&S exposure controls

[Divernoob]

I've read that adjusting exposure controls on P&S's adjusts aperture, but I'm reading posts where folks describe this control as adjusting exposure time, which tells me that it adjusts shutter speed. So if I increase the exposure settings, am I lowering the f stop settings (widening the aperture) or slowing the shutter speed?

 

[bvanant]

Which camera. Many P&S cameras let you adjust either one.
Bill

 

[Divernoob]

Which camera. Many P&S cameras let you adjust either one.
Bill

I'm still working on my lingo, here. The control I was referencing is typically referred to as "exposure compensation." I know that some cameras have Tv and Av control options.

The camera I have now is an L4 Coolpix. From additional reading, it seems exposure compensation features on the more simple P&S's are semi auto functions that utilize both aperture and shutter speed adjustments to accomplish the desired exposure compensation. Does that sound right?

 

[Bubbletrubble]

My understanding of the "exposure compensation" feature is that it alters the exposure settings selected by the camera's metering function without modifying the aperture or shutter speed at all. Since a photographer can only modulate three elements within the camera that affect exposure (aperture, shutter speed, ISO), I would deduce that "exposure compensation" is accomplished through subtle adjustments within digital film sensitivity (ISO). Theoretically, one should be able to test this. But I could be wrong about this. I'm just a simple caveman when it comes to UW photography...

Also, I guess I should mention that my post relates to the "exposure compensation" feature as it is implemented in my P&S (Canon A570).

 

[phillybob]

I'm not up on all the tech jargon, but I know that if you go into the negatives on your E.C. scale, your pics get darker and if you go into the positives, lighter. How it accomplishes that, I don't know. I'm sure one of the other photo geeks can spell it all out for you in a painfully boring manner.

 

[CalgaryDF]

I think that it is some combination of shutter speed, aperture, and ISO depending on what camera you have and the conditions that you are shooting in. I would not be surprised to find that camera companies have their own programs that control the exposure compensation.

 

[olyvtx]

Adjusting the exposure setting (eV or exposure value) does change the camera's exposure metering level. Of course something has to change; shutter speed, f-stop or ISO. What changes depends on the mode that you're shooting.

If you've selected Aperature Priority mode then you've set the aperature your camera will shoot at beforehand. So, changing the exposure setting will cause the camera to change either shutter speed or ISO. Likewise, if you're in Shutter Priority mode then you've pre-determined the shutter speed the camera will shoot and the metering circuitry will vary the f-stop or ISO.

If you're in Program mode the camera with adjust any or all three to compensate for exposure metering.

If you're in Auto mode....ya can't change the exposure setting, it always shoots at 0ev.

 

[Puffer Fish]

For the most part P & S camera's use time... they are very limited in their F stop adjustments. While many have Aperature priority setting... if one has 3 stops worth of adjustment, consider yourself lucky.

That, by the way, is no accident. Image quality degrades with larger F stops.. and little sensors already have image quality issue.. they don't need more problems. And depth of field, with really small lens, is not a major issue.

 

[noreastDIVER84]

I've read that adjusting exposure controls on P&S's adjusts aperture, but I'm reading posts where folks describe this control as adjusting exposure time, which tells me that it adjusts shutter speed. So if I increase the exposure settings, am I lowering the f stop settings (widening the aperture) or slowing the shutter speed?

Adjusting exposure controls could mean a variety of things. If you adjust the ISO(aka film speed) you can get different results. You can also adjust f-stops(lens aperture) Which will yield a different result. You can also adjust shutter speed which will get a different result.

So it really depends on what exposure control you are changing.

As far as my underwater camera goes, it is a point and shoot (Sea and Sea DX8000g) and has manual controls. I have made some adjustments to it and shoot in a program auto mode.

I do work with a Canon DSLR for above water and shoot everything from macro shots to long exposure night shots, to bright daylight shots and even long exposure night macro shots.

Brent

 

[Nemrod]

Exposure determination in most pocket camies is done via a program that evaluates the scene and then exposes per the predetermined program per the mode selected, night mode, portrait mode, outdoor mode etc.

Some bridge/prosumer P&S have full capability for manual control or anything in between and are very flexible shooters, examples are the G11 and S90 Canons.

f stop scale in full stops (lens opening):

1: 1.4: 2: 2.8: 4: 5.6: 8: 11: 16: 22: 32: 45: 64

Shutter speed scale in full stops, how long the shutter is open:

1/15, 1/30, 1/60, 1/125, 1/250, 1/500, 1/1,000, 1/2,000, 1/4,000 seconds

Sensitivity, once called film speed, ISO sensitivity in full stops:

25, 50, 100, 200, 400, 800, 1,600, 3,200 etc

Each full stop--up or down--either halves or doubles the amount of light reaching the sensor (or halves or doubles the sensitivity of the sensor).

Equivalent exposures:

ISO 100, Shutter 1/60, f stop 4.0
ISO 100, Shutter 1/125, f stop 2.8
ISO 200, Shutter 1/250, f stop 2.8
ISO 400, Shutter 1/250, f stop 4.0
ISO 800, Shutter 1/250, f stop 5.6
ISO 800, Shutter 1/125, f stop 8.0
ISO 400, Shutter 1/250, f stop 8.0
ISO 400, Shutter 1/125, f stop 11.0
ISO 400, Shutter 1/60, f stop 16.0


Faster shutter speeds freeze action.

Wider lens openings, lower f stops, decrease depth of field (area or zone of focus)

ISO sensitivity, as it increases with film grain effect increases and in digital noise increases.

N