Knutsford Photographic Society

"The Magic of Photoshop" (Notes)

These notes were taken by club member Tracey Abbott during a club evening in October 2002. The evening focused on the above lecture given by Norman Piper DPAGB, demonstrating Photoshop and Photoshop Elements real-time using a PC, LCD projector etc.

Topics covered :

Automation        Convert to Black & White        General Tips

Printer Calibration        Selective Colour            Sharpening

 

General Tips:

  1. Any adjustments to the original should be done in an ‘adjustment layer’ (Layer, New adjustment layer, choose type of adjustment). This means the original stays as the background and you apply the adjustments like a filter.
  2. Print resolution – no less than 150 was suggested for image resolution. Also only resample once.

 

Convert to Black & White:

  1. Open a new adjustment layer, as channel mixer
  2. Click on monochrome
  3. Move sliders as appropriate
  4. Suggestion that the total value should be ~100
  5. Can save the selections for using later

NOTE: In Photoshop Elements – this channel mix facility is not available so do the following:

1.       Create 3 adjustment layers with hue/saturation

2.       Desaturate the top one

3.       Make the middle one lighter make the bottom one more saturated

Sharpening:

Unsharpen Mask

1.       This is traditional way to do it

2.       Suggest radius at 0.5

3.       Threshold then stops the ‘noise’ being sharpened.

BUT this always leaves an obvious light halo, so :-

Alternative:

1.       Make a duplicate layer (quick way – drag layer over new layer icon on toolbox)

2.       Change this layer to lab colour

3.       Sharpen the lightness channel

4.       Change back to RGB

5.       Blend the two layers, using darken at the top of the toolbox

Alternative 2:

1.       Make a duplicate layer

2.       Go to filters, other, High Pass choose radius between 4 and 8

3.       Desaturate this layer

4.       Then blend the two layers, with soft light

5.       Take the opacity of the top layer down

Printer Calibration:

This was very complicated but here are the main ideas.

  1. Create a test print card, with blocks of pure colour and also with shades of grey. Add a picture if wanted.
  2. Print this page
  3. Make several adjustment layers to make the screen version look like the print. For example an adjustment layer of Hue/Saturation and alter until it gets close to the print. Another adjustment layer for selective colour etc.
  4. When it is as close as possible, make a new layer and then hold alt key and go to menu in top right of toolbox. Choose Merge visible.
  5. Make a copy of the file, and open have both open.
  6. Make the new layer you created look like the original test file on screen – by creating adjustment layers again (this is the reverse of what you just did)
  7. Link these new adjustment layers together, (by clicking in the box next to the ‘eye’)
  8. Hold alt and go to menu in top right of toolbox and choose ‘New set from linked’ – name it corrections
  9. Make a new file ~800x300, call it corrections
  10. Go back to the test file with the corrections and drag and drop the correction set onto the new blank file
  11. Put a text label on the blank page to help identify it (eg paper type)
  12. Open your photograph, make changes as you want them – then just before you print, drag the correction set from the new file onto your photograph. The image on screen will look odd – but when it prints it will be correct.

Selective Colour:

  1. Create a new adjustment level, for selective colour
  2. If you leave it as relative colour, then you can alter the amount of colour in a selective colour – but only in relation to how much of that colour was there in the first place
  3. Change it to absolute colour and you can change the colour a lot more

 NOTE: Photoshop has trouble changing greens, it sees them as yellow.

Selective colour can be used to help add a more interesting sky.

Example:

  1. Take a landscape with a dull white sky, add a new adjustment level for selective colour
  2. Replace white with blue
  3. Choose the mask on the adjustment level and then add a gradient to the sky
  4. Add clouds by painting with a large brush on low opacity

 

Automation:

There are some automated functions (file, automate) that can make life easier:

  1. Contact Sheet – This takes all the files in a specified folder and puts them on several sheets, with several pictures to a sheet. You can define the number of pictures per page.
  2. Fit Image – this constrains the image to certain pixel dimensions. This is useful for creating pictures to be viewed on web pages.
  3. Picture Package – This allows you to print multiple versions of the picture in various formats – eg two big and two small etc
  4. Actions/Batches – Several actions can be recorded and then these actions rerun many times to complete the task. To record the action: Go to the history/actions toolbox. Click on create new action icon, give it a name.It will then record the next actions you do. To replay the action several times: Go to file, automate, batches. For set, choose the name you gave the recorded action. Say where you which directory you want it to perform the action to. Switch off stop for errors otherwise it continually stops.

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