Photoshop CS2 B&W conversion

Each RGB channel (Red,Green,Blue) offers a B&W interpretation that can be used to adjust the color.

1. Create layers from all RGB channels Just copy the individual channels, reselect the RGB composite in the channels palette, and paste them into the same document. Rename the new layers as Red, Green and Blue. Remember to turn off the visibility of the pasted layers before selecting and copying the other channels or you won't copy the true colors.
2. Luminosity layer Explore adding a fourth Lightness layer by duplicating the image and converting to Lab color. Its different tonal structure might be useful. Paste it just above the background layer, below the rest of the RGB layers.
3. Layer masks Create a layer mask for all the layers above the background layer. Adjust the mask by painting in black or white.
4. Opacity tinkering Play with the opacity of the layer as a whole, and also with the density of the mask (the latter is a local change in opacity).
5. Final touches Finally, experiment with a Hue/Saturation adjustment layer as the top layer and the colorize setting.

Subjects with a variety of saturated colors offer greater possibilities.

Action file for CS2/CS3

Double-click this action file to load it into your Action palette. Open an RGB file, and then click the Play button to set up the B&W conversion automatically.

via:Photoshop CS2 B&W conversion. Other methods

Contrast based Photoshop masks

To find a contrasted shape of the object you want to select let's start by choosing a color space:

Color spaces

RGB

• Red channel: Objects that are very red appear light, objects very cyan (red's opposite) appear dark.
• Green channel: Green appears light and magenta appears dark.
• Blue channel: Blue appears light and yellow appears dark.

Lab color

• Lightness: Contains all the tonal (light-dark) information in the picture.
• The a channel: Spectrum from green (negative) to magenta (positive).
• The b channel: Spectrum from blue (negative) to yellow (positive).

Neutral tones (shades of white and gray) will occupy the midline of the a and b channel.

CMYK

Often used for printing, as it mimics the inks used on many printers: cyan, magenta, yellow, and black. It is a small color space, and generally not a good space to use for image editing. It can, however, be a good source of grayscale versions of your photo. Converting between RGB and Lab color has no loss of quality, but CMYK can throw away color information, so it may be useful to open a second copy of your image.

Technique

1. Choose the channel in which your subject is the most prominent (Image>Mode), make a duplicate of it and then play with curves and levels to increase its contrast to get a B&W shape.
2. Copy this modified channel, go back to RGB if you have changed color space, create a new channel, and paste it in.
3. To make sure that the selection will match the original, paste it on top of the image as a new layer, lower the opacity to around 50% and erase the areas that don't match your object.
4. Copying this channel to the clipboard, create two new curves adjustment layers, Alt-click on the layer mask to open up the layer mask and paste into it the mask from your clipboard.Paste it into both adjustment layers, and invert it on one of them. That way you have a mask of your object, and of everything else.
5. To smooth the transition between adjustments, run a 0.7 pixels Gaussian Blur on each of the masks.

You can now modify the curves of the masks separately, or use them to create a selection.

via: How to selectively change parts of your image in photoshop

Curve adjustment layer

A technique to apply localize curve adjustments:

1. Create a curve adjustment layer.
2. Select the alpha channel (all white, as it affects all the image) and fill it in black, hidding the effect of our changes.
3. Paint with a big soft brush over the parts we want to adjust in the alpha channel.

Digital blending

Exposure bracketing with under and over exposure 1.5 stops apart. Lock the exposure and use a tripod if possible.

Open both under and over exposed files in PS and paste one as a background layer on the other. If you have file problems try working in 8bits instead of 16.

Painted Mask

Layer->Add layer mask->Hide all. With a large paintbrush paint over the light part of the image, removing the overexposed part revealing the darker part. Do the meeting line with a small brush.

The layer mask

After pasting the images, add a Layer Mask. Click on the background layer and select the whole image. Copy it to the clipboard. Now hold down the ALT key (Option on the Mac) and click on the white mask rectangle on the Layer 1 palette.

The whole image will now turn white. Next paste the contents of the clipboard onto the white mask. You will now see a B&W mask image. With the B&W mask displayed go to Filter / Blur / Gaussian Blur and set the Radius to about 40 pixels. Click on the Background Layer and you're done. You may want to select the background layer and add an appropriate curve to brighten up the dark area a bit prior to flattening the layers.

via: Luminous Landscape

Flash Value Lock (FV lock)

Subject not in the center

If using flash, it will weight to the centre and the subject will have the incorrect exposure. What you do then is focus on the subject and use the FV lock, let it do the preflashes and lock the flash power. To unlock it, push the FV lock again or set the power off. If you wouldn't use FV lock the flash would lock on the center background and if that is for example a dark landscape would use full power and overexpose your subject horribly.

Shooting several people

Using FV lock will use the same power on all of them.

Fast blinkers

People that blink on the preflash and their eyes are closed on the main flash.

Flash photography basics

Using the flash is combining ambient and flash lights. Flash photography is easier in the dark and is more complicated with lots of ambient light.

Flash as main source of light - iTTL mode

Dim room with little ambient light (home at night). Using the camera manual mode, ISO100, f4 and 1/80th, a picture without flash is dark. With a subject 3m away and a background 9m away, a straight iTTL photo (no iTTL-BL) with the manual settings as before gives a properly exposed subject and very dark background. Using 1/10th, the subject is exactly the same brightness but the background is brighter (and blurred if you didn't use a tripod). As the subject was lit by the flash (typically faster than 1/1000sec), the subject is sharp. The background was lit by ambient light. So in a dim room, the flash exposure of the subject is controlled by the flash metering system and the background exposure is controlled by the settings on the camera. You can adjust them separately! This is the key behind using the flash in TTL mode and the camera in Manual mode.

iTTL system

The Nikon TTL flash metering system is independent from the camera one, even if they share the same sensor and they both need some other information from the camera. The TTL-BL system, in contrast, IS NOT. On iTTL mode, the flash handles the subject exposure and the camera the background. The Camera metering system does not take into account that the iTTL flash will add to the exposure of the subject. In S mode with a fixed 1/80th speed, the camera choses the same f/stop independently of whether the flash is on or not. So if the ambient light is already good enough for the subject, the flash will overexpose it. The Flash metering system just fires the preflashes and looks for the reflected light in a center weighted fashion regardless of which camera metering system you are using or what the camera f/ stop and shutter is set to. Whatever light reflects back from the preflashes plus the ambient from that area determines the strength of the main flash. So, you can reason that the ambient light reflected from the subject is essentially added to the exposure once by the Camera metering system and once by the Flash metering system and overexposure is often the result if the ambient light is strong. So when the ambient light is bright, it is usually best to turn down the flash using flash compensation to about -1.7 ev to start with. This will usually avoid overexposure on especially the subject's face.

The borderline

When the ambient lighting is a little brighter than this, you can still use this technique if you stop down the camera aperture enough to make the flash the primary light on the subject, which takes the ambient light out of the equation. But then your background becomes dark. And if you try to brighten it by decreasing the shutter speed, then the bright ambient light will begin to affect the subject brightness too, and you begin to risk overexposure of the subject. In this situation, shutter, aperture, and flash power all affect the brightness of the subject. It's usually best to simply live with a dark background in this situation and make sure the flash is primary on the subject.

Ambient light as main source of light (Fill flash, outdoor in daylight) - iTTL-BL

When there is a lot of ambient, the background and subject are no longer able to be adjusted independently, and camera manual mode becomes difficult to use. Switch the flash to TTL-BL and the camera to one of the automatic modes (S, A, or P). The camera will then measure the ambient light to set its aperture and shutter and send this information to the flash, after which the flash metering system will set the power of the flash to make the subject the same brightness as the background. If the ambient is extremely bright, like direct sunlight, then it's usually best to select P or S mode (and iTTL-BL), so the aperture will automatically stop down to avoid overexposure. In A mode, the shutter speed will increase to reduce the exposure, but it will be limited by the flash sync speed of 1/250th (D200) and that is often not high enough for bright light if a wide aperture is selected. However, if you really want the shutter to go more slowly, like on a tripod, for instance, all you have to do is switch to 'slow sync'. Then, the shutter will go as slow as it needs to to allow a normal exposure from the ambient. The subject must be darker than the background for TTL-BL to work properly. The flash can only brighten the subject to balance it with the background, it can't make the subject darker. If the subject is brighter than the background to begin with, then you probably are best off not using flash.

iTTL-BL (Through The Lens Back Lit) Fill Flash

Fill Flash is needed any time the background is brighter than the subject. Outdoors on a bright day, if you look closely at the subject's face, you will see shadows in the eye sockets, under the nose, and under the chin. When you shoot this type of shot, it will look much much better if the flash is used to 'fill' the shadows. Or if the background behind the subject is very bright, like sky. Again, flash should be used to 'fill' the subjects face and make it balance with the bright sky. Or indoors during the daytime, to shoot the subject in front of a window with a beautiful brightly lit scene behind, the flash should be used to brighten the subject's face to balance with the bright scene behind. What happens behind the scenes? Situation: Flash in iTTL-BL, Camera in P mode, matrix metering, and AF-S focusing.

1. Half push: Automated focus and camera measurements.
2. The data from the camera measurement are sent to the flash metering system. If the flash head is straight (i.e pointing as the lens) and no diffuser is used, the focal distance from the lens is also sent (only used with no flash modifiers).
3. Full push: Pre flashes for flash system measurements weighted heavily to the center where the subject should be.
4. The flash metering system (which resides in the camera) compares both sets of data and the focal distance if any to determine the amount of power required to make the subject's brightness equal to the overall scene brightness. The flash never tells the camera what power it chose, so for the camera the flash doesn't exist (except for the shutter speed limit).
5. The calculated power for the main flash is then modified by flash compensation that is set on the camera or the flash. This includes the dedicated flash compensation button on the camera, the camera ev setting, and the compensation setting on the flash itself.

For this to work the subject SHOULD NOT be brighter that the background, the flash should be its only light. Fill flash is supposed to be subtle, and when looking at the print it is usually best that you cannot even tell that flash is used at all. So it is usually best to turn down the flash compensation by -1.0 ev to -1.7 ev, so the fill is just enough to lift the darkest shadows on the face without looking obvious. Changing the camera exposure ev while using TTL-BL can produce some strange results, because camera ev affects both the background brightness and the power of the flash. If you don't like the brightness of the background, it is usually best to switch to camera Manual Mode, and set the f/ stop and shutter to give you the background brightness you want. A rule of thumb could be TTL for dark backgrounds, TTL-BL for bright ones.

Lifting shadows in daylight

The slight shadows on the subjects face can be 'lifted' with a very slight amount of flash in TTL mode. Don't use TTL-BL for this.

via: Nikon CLS practical guide

Flash types

i-TTL

i-TTL works by firing a pre-flash before the mirror is raised when you take a picture. The meter evaluates this preflash, as well as other information (Aperture, ISO, selected AF point, AF distance, Flash exposure compensation) and determines an exposure. All TTL flash with the D50 is i-TTL. the flash then fires at the selected power level after the mirror is raised and the shutter opens.

TTL (analog 'Through The Lens')

TTL flash reads the exposure via reflected light off the film to a flash sensor in the mirror box (or the camera meter in the case of the F3). It is more accurate than a pure pre-flash based system, but due to the high-reflectivity of Digital sensors, it doesn't work well for digital. TTL meters only for the flash exposure, ignoring the ambient exposure, this is the mode to use when shooting with the flash as the main light.

TTL-LB (i-TTL Balanced Fill Flash) (D50 default)

TTL-BL balances the ambient and flash exposures so as to use the flash to fill in shadows and bring out the subject. It works fairly well but seems biased to use the flash as the main light. It's better to use TTL-BL with the Flash Exposure Compensation dialed down a stop or so (-1). The on-board flash on the D50 does TTL-BL only, the mode is selectable with the SB-800 or SB-600.
via: Nikon D50 flickr group