Technical Modeling Photography

The amount of sharpening you can get away with, especially the ‘Radius’ settings, depend on the resolution of the image. If it is an image destined for viewing on the screen the resolution of the image should be 72 pixels per inch. (some say 96ppi) If the image is destined for print the resolution should be 300ppi or as near as you can get it to that.

As we are using this on the web, the radius setting should be about 0.4 pixels. So set that first and then set the ‘Threshold’ slider to zero for now. Move the ‘Sharpen’ slider from side to side to see what it will do. Normally you need to move it past 80 to see anything happening at all. If you get all the way to 500 and the picture is still not sharp enough then you need to set the ‘Radius’ higher.

For an image that is 72ppi you should use a radius setting of about 0.4 or 0.5 pixels. Use less than this and you won’t see much happening, use more and the halos will start to look too obvious. For a print image, 300ppi, start with a setting between 1 pixel and 1.7 pixels.

I prefer to use as small a ‘Radius’ setting as possible and push the ‘Sharpen’ slider quite high.

If you are planning to change the size of an image, by this I mean the file size, make sure you do the sharpening after the sizing, especially with JPEGS. Sharpening should be the last thing you do in Photoshop.

I read somewhere a while ago that the ‘Threshold’ slider should be set at about 3 levels. But I find that I use it anywhere between 0 and 20 or so. This is one you have to play with yourself as it really does depend on the type of picture.

The photographic subject can have an enormous impact on how well your camera autofocuses—and often even more so than any variation between camera models, lenses or focus settings. The three most important factors influencing autofocus are the light level, subject contrast and camera or subject motion.

An example illustrating the quality of different focus points has been shown to the left; move your mouse over this image to see the advantages and disadvantages of each focus location.

Note that each of these factors are not independent; in other words, one may be able to achieve autofocus even for a dimly lit subject if that same subject also has extreme contrast, or vice versa. This has an important implication for your choice of autofocus point: selecting a focus point which corresponds to a sharp edge or pronounced texture can achieve better autofocus, assuming all other factors remain equal.

In the example to the left we were fortunate that the location where autofocus performs best also corresponds to the subject location. The next example is more problematic because autofocus performs best on the background, not the subject. Move your mouse over the image below to highlight areas of good and poor performance.
In the photo to the right, if one focused on the fast-moving light sources behind the subject, one would risk an out-of-focus subject when the depth of field is shallow (as would be the case for a low-light action shot like this one).

Alternatively, focusing on the subject’s exterior highlight would perhaps be the best approach, with the caveat that this highlight would change sides and intensity rapidly depending on the location of the moving light sources.

If one’s camera had difficulty focusing on the exterior highlight, a lower contrast (but stationary and reasonably well lit) focus point would be the subject’s foot, or leaves on the ground at the same distance as the subject.
In the photo to the right, if one focused on the fast-moving light sources behind the subject, one would risk an out-of-focus subject when the depth of field is shallow (as would be the case for a low-light action shot like this one).

Alternatively, focusing on the subject’s exterior highlight would perhaps be the best approach, with the caveat that this highlight would change sides and intensity rapidly depending on the location of the moving light sources.

If one’s camera had difficulty focusing on the exterior highlight, a lower contrast (but stationary and reasonably well lit) focus point would be the subject’s foot, or leaves on the ground at the same distance as the subject.