Spring 2012

Spring 2012
by ani

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14

A digital sensor is a linear device — it counts photons, and gives a value which corresponds directly to the amount of light. Human vision, however, doesn't work that way. Our perception of light follows a power curve. So, images made with "flat", unadjusted sensor output look dull and lifeless. Cameras convert this raw sensor data into made-for-use JPEG ...


13

Expanding on Miguel's answer with an illustration, I have in the center a test image gradient with no curve adjustment. On the left I am using a steep curve that pushes my shades of grey closer to extreme black or white, spreading out values near middle grey over a larger range of shades. The effect is that the extreme dark and light areas encroach more on ...


12

I like to think about the tone curve in terms of a function: y = t(x) The input value x to the function is a pixel value from the source image, which is actually the brightness of that pixel. Let's say the values of x can range from 0.0 (black) to 1.0 (white), with all the gray tones represented as real numbers between 0 and 1 (to simplify things a bit ...


11

Highlight tone priority is a camera mode that internally fiddles with exposure to preserve as much detail as possible in the "highlight range" of tones...the brightest tones in a photograph. It does this, however, at the cost of tones in the shadow range, as the ultimate effect is a shift of the histogram down towards the shadows. The cost of shadow tones is ...


9

IntroBased on your questions, I get the impression that you miss one important point, and that is the difference between: light perception in the real world, light perception in the world as humans perceive it, light percetion as your camera's sensor records it, light perception as image formats and your computer perceives (or processes) it. The real ...


6

You could change contrast of individual channel by curves. I'm not sure if this is what you want though, because it will throw out the image color balance. Instead of changing contrast you can change lightness or saturation. This can be easily done in LR - there is a set of individual HSL color sliders for that. If you still want to change contrast and ...


6

There is no equivalent. These scales are completely arbitrary and not measured in any unit! There are no step sizes and no real limits, for example: Some cameras let you go from -2 to +2, -5 to +5, 0 to 9 or even non-numeric scales like high to low. Note that these parameters are subject to interpretation. For example, there are dozens of ways to sharpen ...


5

Highlight priority underexposes by one stop by lowering the ISO, for this reason ISO100 cannot be selected with highlight priority. In post-process the camera compensates for the underexposure, except for the highlights As a RAW shooter you can archieve the same result by underexposing all your shots with 1 stop and then lift everything but the highlights. ...


5

Since Miguel provided an excellent mathematical answer, I'll try to provide a visual and practical analysis of the tone curve tool in Lightroom. To put it simply, it lets you adjust the luminance of the range of tones in a photograph. Lightroom enhances the basic tone curve with four adjustable tonal ranges that can be attenuated, giving you a bit more ...


4

This is one of the few image-enhancement settings that is extremely useful. It is in the custom menu because once you set it, you leave it and do not fiddle with it between shots. When enabled, your camera will preserve more details in the highlights at the expense of some details in the shadows. If your style is to expose for the highlights, then it will ...


4

For most (maybe all) manufacturers/cameras, the picture styles are not applied to raw images and so it just doesn't matter. It may (also dependent on camera/software/software version) change the way the postprocessing is done if the raw metadata tells the software about the picture style used and the software cares about that, but technically it does not ...


4

Your best would be to find a PictureStyle that fits your needs. There's a QuickGuide to Picture Style Settings and Customization pdf that will get you started. It is from the Canon Digital Learning Center.(http://usa.canon.com/dlc) I'd like to quote from this article that's about the adjsutments specific to your camera in the following: Find the Picture ...


4

If your camera supported custom tone curves, you'd be able to get a similar result to this straight out of camera. Unfortunately, yours doesn't, so your only option is post-processing. There are many ways one would get this effect in post. Basic levels adjustment - put the black point output as a value above 0 using a levels control or similar in ...


3

selecting the "Adobe Standard" profile causes the contrast in the blues to be quite noticeably higher than the "Camera Standard" profile I suppose that you should shift blue primary towards magenta and make it less saturated in camera calibration tab. Adobe profiles are essentially a combination of matrix and HSL map. The main difference between camera ...


3

Answering your questions directly: Nikon came out with a new version of Picture Control that has a new file extension associated to it(NP2). Some of the main benefits are: Finer adjustment of each parameter in increments of 0.25 and compatibility with the new Picture Control Flat and new parameter clarity. The D3200 is compatible with NCP, as it is about 2 ...


3

A tone curve is a curve that describes how to turn a shadow, mid-tone or highlight into it's final value for the image you are after. It can add more contrast, reduce contrast or selectively boost shadows, midtones and highlights. These operations can also be done on a per-channel basis (such as red, green and blue) to adjust the colour of a pixel as well. ...


3

Excerpt from an official Canon Quick Guide: Highlight Tone Priority (HTP) All cameras have a fixed dynamic range, from shadow to highlight, that they can capture. HTP shifts some of the available dynamic range from the mid-tones to the highlights to produce smoother tones, with more detail in bright areas. This helps prevent JPEG images ...


3

If you want to evaluate color reproduction and accuracy, you need to use a color checker card. X-Rite is pretty much the source for such devices today, as they purchased Gretag Macbeth some time ago. I personally use the X-Rite ColorChecker Passport, which is a handy pocket-sized clamshell device with the standard colorchecker pattern, an enhanced color ...


3

There are some key differences between a picture style and a white balance setting. While both can affect white and color balance, simply because of the nature of color, the two are intended for different purposes. Picture Styles affect the baseline curves applied to the image when interpolating the raw bayer pixel information into RGB pixels for viewing ...


3

First a brief explanation... A picture style/profile is simply a recipe; it is a means of interpreting the raw data of the sensor. It dictates the tone, contrast, sharpness, brightness, and other ways of interpreting the raw data. When shooting jpeg then these recipes are used in the conversion of the raw to jpeg in camera. So to answer your questions... ...


2

You're right. The picture style only affects JPEG development. The main exception is detailed here — cameras usually use these settings for review (which may affect the exposure decisions you make) and for metering (which may affect the exposure decisions the camera makes). Some RAW converters may use it to set defaults; others will ignore it. Many viewers ...


2

Picture Styles generally don't affect white balance per se, but they do affect colour balance. For example, portrait styles increase red channels to provide warmer skin tones, and landscape portrait styles boost the blue and green channels for more vivid scenery and skies.


2

You are using the wrong term to define what you wish to accomplish. The examples you show are different due to the increased SATURATION of the hue of the sky. Sliders in most every software for image manipulation allow you to choose the specific colour channel and to effect the change you wish. There are three variables when talking about any specific "...


2

Since it will vary from camera to camera, the easiest way to find out what the equivalent is for a specific camera would be to test it yourself. Set the camera up as neutral as possible. In the case of your Canon 5D Mark II, that would be the 'Neutral' picture style. Then take a series of RAW+JPEG photos with the contrast set at -4 to +4 in one step ...


2

The global tonemap module fills a different role than the generic tone curve. Since its purpose is to compress the wide dynamic range of an HDR or RAW file in a specific way based on theories of human perception, it occurs earlier in darktables fixed-order processing pipeline, allowing the modules that follow to operate on this compressed range. It also ...


1

I think the quickest way to do that would be to use the adjustment brush and draw the effect in the desired area. Choosing the area by globally selecting the desired color (or hue, for example), means all areas with that color in the image are affected. This can lead to strange situations like changing the contrast in the sky means changing the contrast in ...


1

One stop is a factor 2 of light (-1 stop => half the light, +1 stop => twice the light). So a byte (8 bits) has a dynamic range of 8 stops. It's less than a good camera, which can have up to 13 or 14 stops of dynamic range. So how do we deal with this problem? It is impossible to put 13 bits of a raw file into the 8 bits of a jpeg file without losing some ...


1

I assume the gray card is 18%. Then compared to a maximum reflectance of 100%, the linear stops are each half, or in steps of 100%, 50%, 25%, 12.5%, 6.25%, etc. So 18% would be around 2.5 stops down. But it will NOT look like that in your histogram, because all RGB data in camera histograms is gamma encoded, which is a different story. In a gamma ...


1

There are two aspects to this question: Softness These images have a very narrow depth of field - the subject is in focus and everything else is very soft. This is purely the result of using a very wide aperture, available only on a prime lens at its widest aperture, and probably a full frame or larger sensor. Zoom lenses won't go wide enough in ...


1

My approach would be playing with: Lower the saturation. The curves or levels (to overexpose). If you use the levels use the gamma slider (midtones). A gradient map. I see some additional steps there like masking the bride, working some tones there, and applying the blue to the rest of the background. Remember to work new effects in new layers. You can ...



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