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Make a stepwedge

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Old 06-14-2002, 03:12 PM
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Doug Nelson Doug Nelson is offline
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Make a stepwedge

This is a great way to learn how PS alters tone. It can also be included in other images as a reference.

Make a long, thin new RGB image (10-20 times wider than tall). Select the linear gradient tool, hold down the shift key, and drag from the far left border to the far right border (but no further). Posterize with 21 steps. Save as PSD or TIF.

Use this to see the effects of curves, levels, USM, and many other common tonal adjustments. Put it at the border of an image before you start work on it. You'll be amazed at how clear some abstract concepts become.

You can also make one about 3x the height, repeat, only add the final step of selecting the middle third and inverting. This one won't be of much use with your images, but really punches home some of the damage that can be done.
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Old 06-14-2002, 04:05 PM
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Jakaleena Jakaleena is offline
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Excellent tip, Doug!

I've used step wedges with the densitometer in a lab to balance various things, but hadn't thought of using one on my PS image. I'm going to give that a try...

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Old 06-14-2002, 04:07 PM
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d_kendal d_kendal is offline
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Thumbs down

thanks Doug, that one'll be really usefull to me.

- David
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Old 06-14-2002, 06:54 PM
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Ed_L Ed_L is offline
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That's a great way to keep aware of what's happening. It seems like it would be a lot easier to see in the step wedge than while viewing a print. Thanks.

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Old 06-14-2002, 08:52 PM
Stephen M Stephen M is offline
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Step wedges can be great, often 11 or 21 step posterization is used...also it can help to disable the noise dither in the gradient tool when making a gradient for this task - but in most other cases you would always want the dither option turned on for the gradient tool, as this can stop banding.

I like to select approx 2/3 of the width of the entire strip to posterize - leaving a small strip of the full gradient intact to compare with the step patches.

Brian Lawler has a good vector EPS 100 step wedge which you can rasterize into Photoshop - but depending on the workspace mode you rasterize to and what profile you have setup, the tonal patches may not translate to true 1% grayscale increments: (stuffit expander required)

The step wedge/gradient can also be used to understand the neutral or gray balance of a device, usually CMYK but it also applies to RGB devices. Simply convert the test strip into the CMYK or RGB device space used for output and inspect the numbers. Setting the colour mixer palette to grayscale ramp and CMYK or RGB sliders is a good way to do this on the fly - simply drag the eyedropper along the grayscale ramp and read the values found in the sliders for the colour palette, instant feedback on gray balance for any tone!

One word of caution - keep in mind that although having a step chart can help to show what is taking place while colour and tonal edits are taking place, it is the actual image content that matters. Dont freak if your step wedge is compromised in certain tones, as your image may behave differently due to different tonal range.

Placing fixed samplers (found under the eyedropper tool or use shift with the eyedropper) and the info palette are tools that I cant live without in my prepress duties - often knowing the mix of ink is more critical than simply trusting that the monitor is indeed indicating the correct colour or tone, and even when colour is not important, as in shadows - knowing the ink mix is very important.

The layer options blend if sliders are confusing to many people - but when you understand them they open up many new oportunities, I think they are so critical that I encourage them as the first thing learned when layers are introduced - even before layer masks! I think they are that important...these gradients and step wedges can be helpful when exploring what the Photoshop layer option blend if sliders are doing.

Hope this helps,

Stephen Marsh.
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Old 06-14-2002, 09:18 PM
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fugitive fugitive is offline
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Are they supposed to be flashing?
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