Did it ever occur to you to consult the documentation, Mark. Say, the User Guide and/or the Help files?

Exposure command

Adjusts tonality by performing calculations in a linear color space. Exposure is primarily for use in HDR images. See Adjust Exposure for HDR image.

Adjust Exposure for HDR images
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The Exposure adjustment is designed for making tonal adjustments to HDR images, but it works with 8‑bit and 16‑bit images. Exposure works by performing calculations in a linear color space (gamma 1.0) rather than the current color space.

1. Do one of the following:
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Click the Exposure icon or an Exposure preset in the Adjustments panel. *

Choose Layer > New Adjustment Layer > Exposure.
Note: You can also choose Image > Adjustments > Exposure. But keep in mind that this method makes direct adjustments to the image layer and discards image information. Adjustment layers for 32-bit images are available in Photoshop Extended only.
2. In the Adjustments panel, set any of the following options:

Exposure
Adjusts the highlight end of the tonal scale with minimal effect in the extreme shadows.

Offset
Darkens the shadows and midtones with minimal effect on the highlights.

Gamma
Adjusts the image gamma, using a simple power function. Negative values are mirrored around zero (that is, they remain negative but still get adjusted as if they are positive).

The eyedroppers adjust the luminance values of images (unlike the Levels eyedroppers that affect all color channels).
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The Set Black Point eyedropper sets the Offset, shifting the pixel you click to zero. *

The Set White Point eyedropper sets the Exposure, shifting the point you click to white (1.0 for HDR images).
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The Midtone eyedropper sets the Exposure, making the value you click middle gray.

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Apply the Brightness/Contrast adjustment
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The Brightness/Contrast adjustment lets you make simple adjustments to the tonal range of an image. Moving the brightness slider to the right increases tonal values and expands image highlights, to the left decreases values and expands shadows. The contrast slider expands or shrinks the overall range of tonal values in the image.

In normal mode, Brightness/Contrast applies proportionate (nonlinear) adjustments to image layer, as with Levels and Curves adjustments. When Use Legacy is selected, Brightness/Contrast simply shifts all pixel values higher or lower when adjusting brightness. Since this can cause clipping or loss of image detail in highlight or shadow areas, using Brightness/Contrast in Legacy mode is not recommended for photographic images (but can be useful for editing masks or scientific imagery).
Note: Use Legacy is automatically selected when editing Brightness/Contrast adjustment layers created with previous versions of Photoshop.

1. Do one of the following:
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Click the Brightness/Contrast icon in the Adjustments panel. *

Choose Layer > New Adjustment Layer > Brightness/Contrast. Click OK in the New Layer dialog box.
Note: You can also choose Image > Adjustments > Brightness/Contrast. But keep in mind that this method makes direct adjustments to the image layer and discards image information.
2. In the Adjustments panel, drag the sliders to adjust the brightness and contrast.

Dragging to the left decreases the level, and dragging to the right increases it. The number at the right of each slider reflects the brightness or contrast value. Values can range from ‑150 to +150 for Brightness, ‑50 to +100 for Contrast.

Mark_B_Anstendig

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