Wednesday, April 29, 2009

Which lenses autofocus on a D40, D40X, D60 or D5000?

The low range Nikon cameras D40, D40X, D60 or D5000 can only autofocus with lenses with built in motor, for example Nikon's own Silent Wave Motor (SWM). These cameras lack autofocus motor themselves - something which makes them smaller, lighter and cheaper.

Nikkor lenses with "AF-S" in their name should auto-focus on these cameras.

Sigma lenses with "HSM" (Hyper Sonic Motor) in their name should auto-focus on these cameras.

There are also a number of Tamron lenses that should auto-focus on these cameras, but I have not found any reliable way to tell which ones. The secret letters to look for may be "di" (digitally integrated), but there seems to be no confirmation that it is a fool proof sign.

Sunday, April 26, 2009

Using "hidden" NEF data in Photoshop or Aperture

If you shoot raw nef files with your Nikon camera, you may have camera settings that are not readable by non-Nikon applications. One of the most striking ones is if you choose to set the picture controls to create a black-and-white picture. When you open that nef file in Photoshop or Aperture, for example, the colour will come back.

To see this kind of information in non-Nikon applications, you will have to convert the files in a Nikon application. You can for example batch process all your nef files to jpeg or tiff format using View NX (menu File > Convert Files...) or Capture NX (menu item Batch). Then import the tiff files to the other application.

But don't forget that conversion from nef to both jpeg and tiff will lose some data. Tiff is a lossless format, but the only thing that is lossless is what is visible. In the nef file you can always go back and change the picture controls to some other setting. However, there is no way you can get the colour back in a black-and-white tiff file. In other words, it is always good to keep the nef as backup, in case you need to make some other modifications.

Chromatic Aberration

Chromatic aberration is a consequence of the fact that light of different colours do not focus on the same plane when they go through glass. Think of a simple prism, where white light goes in and a rainbow of colours come out.

Camera lenses are not always good at compensating for this, and the result may be a blue thin line around objects.

To get rid of the line semi-automatically, you can use tools like:
  • Adobe Photoshop - Filter > Distort > Lens Correction. Adjust the slides in the box "Chromatic Aberration".
  • Adobe Camera Raw - Open the file. (If it is not a raw file, you right-click on it in Bridge and select "Open in Camera Raw..."). Click on Lens Correction. Adjust the slides in the box "Chromatic Aberration".
  • Capture NX - In the Edit List, click on "New Step". Select Adjustment > Correct > Color Aberration Control.
You can also manually replace the colour using things like the "Hue and Saturation" adjustment in Photoshop or the Gimp. In Photoshop you can also use Image > Adjustments > Replace Color.

If you do not succeed in getting rid of the chromatic aberration, do not feel bad about it. It is a tricky thing to handle. Good software takes into account the camera and the lens. As an example, Canon's RAW editing software Digital Photo Professional does not make the Chromatic Aberration correction tool available for pictures taken with the Canon EOS D20. Neither does it attempt to correct TIFF or JPEG pictures. This is undoubtedly because Canon knows they cannot make good enough corrections for those pictures.

Wikipedia has a more information on the subject.


The Lens Correction tab in Adobe Camera Raw.


Example of a picture with both green and red chromatic aberration.

Detail showing red aberration on one of the birds.

Detail showing green aberration on another of the birds.