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Photoshop Tips V

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The following are posts written to the Usenet Photoshop newsgroups.

Unsharp Mask

There's a lot to knowing how to use it for different images. Keep learning. Also, it depends on your expectations. All Unsharp Mask really does is enhance edge contrast--it won't bring out-of-focus images into perfect focus.

Here are some quick tips:

For color halos you can Edit>Fade to Luminosity mode afterwards (or use Lab mode, as suggested). 

You can make two copies of the sharpened image and use Darken and Lighten modes with different opacities to reduce "over-brightening".

You can select just the edges for sharpening using the High Pass filter, or other edge detection techniques. Blur the edge selection for a less abrupt look.

Getting the ideal radius value is important, and that depends on the size of detail you want to enhance (and preserve) in the image. A portrait (human face) would generally require a larger radius, smaller amount. An image with lots of fine detail would probably benefit from a smaller radius and a higher amount.

Use higher threshold values to limit the sharpening to areas that already have a certain level of contrast. Multiple sharpening with lower values can produce better results than one big move. Sharpen individual channels--the ones with less noise.

Vary the effect: Sharpen a copy and use a layer mask to soften the sharpening where needed, and use the Sharpen Tool on small important areas that need hard sharpening.
--  Ross 

When you apply the Unsharp Mask filter to a color image, the filter automatically adjusts each color channel causing unwanted halos around the edges of your image. To keep this from happening, convert your image to Lab mode by choosing Image > Mode > Lab Color. Then apply the Unsharp Mask to the Lightness layer only in the Channels palette. This will bring out the detail without affecting the colors of your image. j
Levels

Q:  I'm still not 100% clear on the "levels" control. In other words, I can use it do enhance the picture, but I'm not sure if I understand it 100%.

From the terms "input levels" and "output levels", it seems as though this acts as a function, with the input being the pixel values of the image, as presented in the histogram, and the output being a remapping of those pixel values, with the high value of the input - say it was 240 for example, being normally remapped to 255 in the output value. Is this correct?

It looks as though the output values might normally be left at 0 and 255, and the input values adjusted, such that the darkest pixel now maps to 0, and the lightest pixel maps to 255. The problem that we normally might find would be no pixels in the image at the 255 level, so we set that level to where we find the brighest pixel.

It would also seem that the gamma input value would be understood to be remapped to a gamma of 1.0, in the output level. Am I correct in my interpritation of this whole levels control?

The thing that confuses me is that the gamma seems to affect the brightness to such an extent. If the gamma is only the middle grey tone, why does it have such an impact... Or is gamma more of a range of tones? --Garry Burgess

A: Yes, when you set new levels all (or most) values in the image are remapped. Otherwise, you'd get abrupt transitions that would be unsightly.

The Output levels determine what range you're mapping to. If you set the black output level to 5, and the white output level to 240, then those will be the minimum and maximum values you get. The Input levels set what values you want to define as black and white (or minimum and maximum if you've narrowed the range with the output levels). The middle slider adjusts midtones. If you move the white input slider inward to 215, then pixels with a value of 215 become 240 (as set above) and values lower than 215 are stretched upward to create a smooth adjustment.

If you move the black slider inward to 23, then pixels with a value of 23 become 5 (as set above) and values higher than 23 are stretched downward. If you move both input sliders inward, you stretch the dynamic range in both directions, ending up with values between 5-240 (as set above). The middle input slider sets where 50% gray is. It starts out right at 50% - no remapping. Move it left and you define a darker gray as 50% gray, which makes midtones lighter. Move it right and you define a lighter gray as 50% gray, which makes midtones darker. Values around the mid point are proportionately stretched and squeezed to make a smooth visual transition.

Black and white points are like fixed tacks on two ends of a rubber band. You can adjust the midtones without clipping the shadows and highlights, as the middle slider has progressively less affect there. Curves can work just like Levels, with the added control you get from being able to map any value to any other value exactly as you wish.
-- Ross

Image Formats

Briefly, these are the formats in common use and their usual applications:

PSD : Images with more than one layer. Retains all Photoshop-specific elements. Safest format for editing. Use PSD unless you have a reason not to.

TIFF : Images to be transferred to other apps that don't support PSD. Lossless LZW compression an option.

EPS : Images to be placed in a page layout program (CMYK, Grayscale, Bitmap, or Duotone modes most common). Use a "Clipping Path" for transparency.

DCS 2.0 : version of EPS used for images with spot color channels.

JPEG : Full-color (photographic) images for web pages or email. Can also be used for archiving (high Quality setting recommended). No transparency.

GIF : 256 color (or less) images or bitmap text for web pages or other screen graphics. Supports transparency.

PDF : Images to be displayed and/or printed with Adobe Acrobat. Good for printing to non- PostScript printers.

BMP : Limited Windows format. No alpha channels. Use only if some Windows application requires a BMP. Convert to Indexed or Bitmap mode before saving to get 8 or 1 bit options, respectively.

PNG : Some advantages, but not necessary for any particular application. All features not universally supported.
-- Ross

Resolution, image size, and file size are all related. Think of your image like a tile mosaic. Each tile is a single pixel. Resolution determines how big those tiles are--that is, how big each pixel is. If an image is 72 pixels per inch, then each "tile" is 1/72 of an inch across. Likewise, if the image is 300 pixels per inch, the tiles are 1/300 of an inch across.

Resolution and print size are related in a very simple way: The number of tiles, multiplied by the size of each tile, gives you the total size of the mosaic. If a tile mosaic is 100 tiles wide, and each tile is half an inch across, then the mosaic is 50 inches wide. Likewise, if you have an image which is 300 pixels per inch, and it's 600 pixels wide, it is 2 inches wide.

Similarly, a picture which is ten inches wide and is at 300 pixels per inch must be 3,000 pixels wide. When you create an image for printed output, it is not always true that the higher the resolution is, the better. An ink-jet printer does not print a better image from a 600 pixel per inch image than it does from a 300 pixel per inch image, for a variety of reasons.

Similarly, an image printed on a printing press (say, in a magazine) does not benefit from a very high resolution; all images printed on a press are broken up into halftone dots, and the ideal resolution depends on how fine those halftone dots are.

When you look at an image on your screen, the image will seem to be very large, because what Photoshop says is "100%" magnification is not the size the image will print! When Photoshop shows you something at 100% magnification, what it means is that one pixel on your screen equals one pixel in your image; you are seeing "100%" of the number of pixels that will fit on your screen. An image that is two inches wide at 600 pixels per inch is 1,200 pixels wide--it will more than fill your 1,024x768-pixel monitor, even though when it prints out it will only be matchbook sized.

You can change the image size of an image in two ways: by using interpolation, which changes the number of pixels, or by not interpolating, which leaves the number of pixels the same but changes the size of each pixel.

For example, let us suppose that you have an image that is 10 inches wide and 300 pixels per inch. It is 3,000 pixels wide. If you shrink it to 5 inches wide, but you have interpolation turned off, the number of pixels will not change. The image is still 3,000 pixels wide, but it is only 5 inches wide; therefore, it is now 600 pixels per inch.

Now, let's suppose you shrink the same image to 5 inches wide using interpolation. Photoshop will change the number of pixels. The image will now be 5 inches wide, and it will still be 300 pixels per inch, so it will now be 1,500 pixels across, instead of 3,000 pixels across.

Q:  I then get confused by the dpis on my printer which is 2800 x 720. How does this relate to the DPI of the document and why is it one number x another number?

A: Well, you are misusing terms. Not your fault; scanner manufacturers do this, too. A picture in Photoshop does not have a "DPI." DPI stands for Dots Per Inch. Printers print dots. A Photoshop picture is made of pixels, not dots. It is measured in Pixels Per Inch, not Dots Per Inch. When you print something on your printer, one pixel is made of many printer dots. For your inkjet printer, a resolution of 300 pixels per inch is all you will ever need. Your printer has two numbers--2880x720 dots per inch --because the printer's dots are not square. They are rectangular. The longest side of one addressable dot is 1/720 of an inch. The shortest side is 1/2880 of an inch. --TacitR

Differences in the Photoshop versions

By no means an all inclusive list here, but... :::pulling out the Getting Started booklets from v4, v5 and v5.5::: v.4 --- -Tool Tips -Contextual (right click) Menus -Adjustment Layers -Digimarc Filter -Navigator Palette -Support for 16 Bits/Channel Images (limited) -Batch Processing (sorta worked most of the time) -Actions Palette (commands in v3) -Guides and Grids -"Hidden" Tools (flyouts on the tool palette) -Color Dodge, Color Burn and Exclusion Blend Modes -New Transform features (including Free Transform) v.5 --- -History Palette -Layer Effects -Editable Type -Layer Alignment Commands -Expanded support for 16bit color -New color management -Channel Mixer -Spot Color -Measure Tool -Magnetic Pen and Lasso -Freeform Pen Tool -3D Transform Filter -PDF Import -Postscript Level 3 support -DCS 2.0 Support -Expanded Scratch Space support (200GB on 4 volumes)

v.5.5 --- -Save For Web dialog and new web features -Magic Eraser Tool -Background Eraser Tool -Extract Command -Art History Brush Tool -Contact Sheet II, Picture Package, Web Photo Gallery exporters -Auto Contrast -Contiguous in Wand and Bucket Tools -Simulated Type Styles -New Indexed Color options -GIF and PNG transparency -Expanded TIFF Support (deflate and jpeg compression) -New JPEG save options --  -Steve
Books... Which one is best? Tutorials seem so specific.

Actually my tutorials are not as specific as they might seem. I take some pretty broad topics and then put them into fun little projects.  However if you don't want to deal with tutorials, there are many great books out there, too. Everyone has a different style of learning, ways that they are comfortable learning things, reading, etc. What i enjoy reading, you may find to be just hogslop. As you discovered with the manual, though, it is important that you are engaged in the reading, or you won't stick with it, and therefore, your learning will be limited. So what you need to do is to evaluate the books based upon YOUR learning style. Here's how to do that:

> Go to your local big bookseller. > Pull out several PS volumes. Pick ones whose covers you find attractive, whose titles you like, or books you have heard of. > Before you open any of them, decide on some topic that you want to read about. For example, you might choose "using the lasso tool."  > One at a time, go into each book and read only that section about the lasso tool.  > Reject any books that talk to you in a way that makes you uncomfortable at all. If a book talks down to you, is too complex or doesn't have enough pictures, or whatever you don't like, get rid of it. This may seem like little stuff, but you want a book whose author you "get along with." There is a reason that there are so many PS books and that there are so many that sell well. We like different things!  Good luck in your book search! -Janee
Vector Capabilities of PS 6 Q:  I am using Photoshop 5.0 right now, but was recently told by a Photoshop rep that Photoshop 6.0 has vector capabilities now. Can anyone who is using 6.0 tell me more about its vector capabilities .... what you are doing with it and how it compares to Illustrator or CorelDRAW?  A: Photoshop's vector capabilities are very useful, but they do not measure up to a vector app like Illustrator, Freehand, or CorelDraw. One important advantage of vectors is the ability to rescale objects without loss. You may already be aware of the fact that when you scale a graphic defined by vectors, a brand new bitmap is created (rasterized) that is nice and sharp, and smooth for low res output if anti-aliased. This flexibility makes designing much easier, and the art can be optimized for any output. Another important advantage of vector art is that it can be used for multiple purposes, which is crucial for making logos. A logo is something that needs to be output many different ways, and at many different sizes and resolutions. Photoshop 6 does not provide adequate tools for making professional logos. PS 6 has several useful vector tools. You're probably familiar with the Pen tool from earlier versions, but now you're not limited to making the kind of paths that are not really a part of the image. You can now make shape layers with it, as well. There are also shape tools that make round-corner rectangles, stars, ellipses, etc, as shape layers. You can make your own shapes, as well. A shape layer is a solid-color layer that is clipped by vectors. IOW, a red star is a layer filled with red, with the red only visible inside the vector star shape (you can group the layer, so it's not limited to being filled with a solid color). You can edit the shapes like any other path. You can specify layer effects, (which are more robust in PS 6) to the shape layer and you have scalable objects with drop shadows and all the other effects. As with selections, you can cut a hole in a vector shape easily, or add, or intersect. All of the Transform commands work on shape layer paths. The vector tools available in PS are not nearly as extensive as Illustrator. You don't have the Pathfinder filters, stroking options, brushes, blends, pencil reshape as you draw, gradient mesh, type on a path, flowing paragraph text around objects, vector filters, Stretch tool, working with compound/grouped paths, and many path editing options, to name a few. If you know how to use Illustrator, you can make a very wide range of graphics where the whole object is scalable. In PS, it's hard not to have to use bitmaps for many things that could be done with vectors in a vector app. As far as printing goes, Illustrator makes PostScript files, which are the bulk of professional printing. PS is very limited for vector output, although you can make PDF files. You must have a real vector app if printing is your business, and many feel that Illustrator is the best solution.  --Ross
Lighting in difficult situations

This isn't a Photoshop problem, but a photography solution. This came from Jon Shearer in the myJanee.community in answer to Tommy, who was wondering how to do a photo in a dark forest:

I can visualise what you are trying to achieve with the mossy forest photos (I often visualise these when I listen to Sibelius' Finlandia or Orff's choral masterpiece, Carmina Burana) I am assuming your camera has manual control and that the light level in this area will be quite low (coz moss does'nt like much sunlight). The digital medium is great for experimentation because you get an instant result, so here is where I'd start:

1) Use a tripod and remote release.

2) Depending on the range of apertures you have on your lens, take a meter reading directly on the moss using aperture priority and the aperture 2 f stops in from wide open. Now this will probably indicate a slow shutter speed. That's ok.

3) Let us say that the meter indicated a shutter speed of 1/4 sec. Switch the camera mode to 'shutter priority and set the shutter speed to 1/4 sec.

4) Now with the camera with its shutter speed locked in, take a meter reading on the lightest part of the scene you will be shooting. The aperture will now indicate the correct exposure for the highlights.

5) What you need to do is to leave the shutter speed set at 1/4 sec and go to full manual override.

6) You know the aperture range from the readings, so start to shoot using the smallest aperture (the one indicated for the highlights)

7) Continue shooting, the next shot 1/2 an f stop wider.

8) Keep on shooting, the next shot 1/2 an f stop wider again.

9) Do this until you see an acceptable shot.

I hope this has'nt confused you and I'll be pleased to elaborate on any points. After you have done this a few times it will become second nature in this kind of situation. There are other ways to do the same thing but try this method and see what you think.

On the subject of filters. Here is a link to the filters I used to use. Have a good look around in there because they have an amazing range.

Jeanie, once again offers some great advice on the sunbeams but you could also use the method for these as well.

There is also some good info here on Ansell Adams' Zone system for exposure. It's for b&w but can be applied to colour as well.

Keep something else in mind. Because you will be taking the exact same shot on a tripod, you can always merge the shots with the correct exposure for the dark area with the shot with the correct exposure for the lightest area using PS.
--Jonss

Thumbnail-Producing Action

Here is a tip that came from Fragle, in answer to a question that I've been having.

Janee wonders how to make an action to make thumbnails.

Fragle:

This is the way to make thumbnails:

  • Create a new action.
  • Press Record. do the image resize.
  • Then press File > Save for Web.. Select the settings you want...
  • Press OK and the Save As dialog pops up...
  • Save the image to a temp folder, press OK.
  • Close the image, and on the question "Save," select NO.
  • Press STOP.

To save the batch

  • File > Automate > Batch.
  • Select the new action, select Source and Destination: None
  • The thumbnails are now saved in the Temp folder.

If you use an original and then save one large for web and then a thumb for web, as I do, this can be done in one action. Just add another "Save for Web" in the action and select another folder...

Note: You must remember to delete the files from the temp folders before you do the batch on a new set of images.

Janee: i still don't know how to get the thumbnail sized though. Like... i want 100 pixels on the longer side. How do i tell it that?

FRAGLE (12:15 AM) : When you make the new action and press the "record" button you use the menu "Image -> Image Size" as normal, and select 100px width and OK... Then you see that i is added to the action...

From the myJanee.community:

Here's a quick tutorial on how to create a 3d sphere with reflections in Photoshop.

  1. Open a new document: dimensions 500px by 500px (or any SQUARE document).
  2. Make a new layer and fill it with any pattern -- ordered patterns work best (like my circles) -- call it circle. Create a circular selection that almost fills the image. Filter > Distort > Spherize 100%. Select > Inverse... Delete. Deselect.
  3. Make a new layer above the circle layer. Create a selection from the circle layer (Ctrl-click circle layer in layers palette). Choose the radial gradient white to black and drag the gradient tool in the selection from top left to bottom right. Change the Blend Mode to Multiply. Deselect.
  4. New layer at the top of the stack. Fill with black.
  5. Filter > Render > Lens Flare 50-300mm zoom ...100% keeping the flare pretty central, but originating slightly towards the top left.
  6. Filter > Distort > Polar Coordinates - Polar to Rectangular.
  7. Edit > Transform > Flip Vertical
  8. Filter > Distort > Polar Coordinates - Rectangular to Polar.
  9. Load the circle layer as a selection. Select > Inverse... Delete.
  10. Set Blend Mode to Screen.
  11. Link the three layers together and resize to fit.

--Jamie Brown

Jamie's sphere
j j

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