Every time you divide the card in half, you will see the view of double the previous focal length.Not sure where you get 135 as the standard for portraits in film days? The 85 was considered king of portraits when I was learning photography in the late 70s.

If you divide the card in half, both horizontally and vertically, you'll see the view of a 100 mm lens. On the crop 'C' sensor, move the card out to 18 inches from your eyes. Note: if you take a 4 x 6 card and hold it approximately 12 inches from your eyes that will give you the basics you that you get from a 50 mm lens on a full frame camera.

To maintain an aspect ratio between full frame and crop 'C' sensor, Divide the full frame lens focal length by 1.5. to calculate the lens focal length equivalent, multiply the actual lens focal length by 1.5. you can shoot portraits with a 50 mm lens, but you will not get the best prospective. Any prime lens close to that with a sufficient aperture size should do find. For a crop C sensor A 90mm would be equivalent. They are located towards the bottom of the tool pane, when in Develop mode.Traditionally on a full frame 35mm, a 135mm is considered a portrait lens. Users of Adobe Lightroom also have the ability to easily fix this problem by using the Lens Correction settings. The image below on the left has quite severe purple fringing, but after a software tweak, it’s all gone! Not only does this software correct chromatic aberration, it also does many other lens corrections such as pincushion/barrel distortion, vignetting and perspective. The trial lets you correct up to 10 images, but a full licence is only US$25 anyway. However, I today discovered this neat little app which has a database of thousands of lenses and can correct a number of common distortion and aberration problems for you. I’m sure if I were using the ultimate in lens quality – the Canon “L” series, I would not have the same problems but unfortunately, I’m not. As a result, the images are all very high contrast with the areas of detail very small (such as twigs, leaves, very small birds, etc.) Unfortunately, these are perfect conditions for chromatic aberration problems to occur – and they have. More specifically, small birds trying to find food in the snow.

I’ve been taking a few shots of birds over the last couple of weeks.

Epaperpress ptlens