Evaluating images in Photoshop on your computer screen.

Ok, so you have opened up your image in Photoshop after carrying out the RAW conversion - (or have opened the jpeg if you are still shooting jpegs- and shame on you if you are!). The next thing you will do is make any subtle image adjustments such as levels and hue/saturation, and finally, as the last step - sharpen using unsharp mask.

I have done just that with this image of a red-breasted goose. The image fills the screen, and looks very nice. However, it is still destined for the bin ! Why ? because I haven't been critical enough in my evaluation method to judge if the image is truly sharp.

Once in Photoshop, if you click on the magnifying glass tool in the tools (on the left of the screen in my example above) you will then notice that a new toolbar opens at the top of your screen with three tabs labeled"Actual pixels", "Fit screen" and "Print size". Click on the "Actual Pixels" tab and the image will appear huge on the screen. It is now at 100% or actual pixels. If you want to move the image around, use the hand tool. The image now will look a bit soft, but that is normal.

Let's now do it the right way. Open the image from the RAW converter (or open the jpeg - yuck) and click on the magnifying glass and then click Actual Pixels.

Now look at the goose's back - labeled"A" below. There is a nice crisp black line between the goose's back and the mud behind. Now look at "B" - notice how the black edge of the head is a little blurred (ghosting) ? The eye also looks rather soft compared to the back. Finally look at the beak - "C" there is obvious movement in the lower mandible that we didn't notice before.

Basically, what is going on here, is that the shutterspeed was too low for the grey old day on which I took this picture. Although tech body was still, the goose moved it's head just a little, and also started opening it's beak. Result - motion blur - a poor image that I will discard. If I had only viewed at "Fit screen" proportions, I would never have noticed this until I had printed the image out. Never mind - it served a purpose to use an example in this tutorial.

Whenever you sharpen an image, it is also imperative to carry this out at l00% size. When I look back at some of my earliest digital images, I can see that when I now view them at 100%, I have often over-sharpened them - I can sometimes see halos and jpeg artifacts in some of my old jpegs.

The RAW's I have been able to rework in the light of my improved knowledge. The jpegs I have had to dump! How many more reasons do I have to give you to shoot RAW?

Here is a crop from the 100% image which I purposely over-sharpened to demonstrate halos. This image looks pretty good when just filling the screen - but looks dire at "Actual Pixels".

One last thing - when you enlarge images using the Magnifying Glass tool (or Navigator) you may have noticed some odd jagged edges at certain magnifications. This is just an odd effect that you get in Photoshop when you view at magnifications such as 33.3% or something. If you view at 100% or an even whole number such as 20% or 50% these should disappear - they are not real - just a screen effect.