Get the DA560 or just crop from a 400mm lens?

By PF Staff in Articles and Tips on Mar 17, 2013
Get the DA560 or just crop from a 400mm lens?

As a side effect of our ongoing review of the Pentax DA 560mm super telephoto, we were wondering how big of an advantage the 560mm would have over a cropped image from a shorther lens like a 400mm.

For this purpose we took some comparative test chart photos using the FA* 400mm F5.6 (Pentax's most recent 400mm lens) and the 560mm, both at F11 and ISO 100 with the K-5 IIs. The images from the 400mm were cropped so that both lenses achieved the same effective field of view.

The full image of the chart when shot with the DA 560mm looked like this - we have marked the crop used below for the comparison:

The width of the visible part of the chart above is 11.8 inches.

When shot with the FA*400mm the chart looked like this when shot from the same distance, due to the wider field of view of the lens:

For the first comparison we cropped the area in the red frame to 3 inches wide at 240 dpi (720x582px). Click on the thumbnails to enlarge:

DA 560 mm FA* 400 mm

There is no real difference between the two images at this size.

In the next example we crop to a width of 4.7 inches and 240 dpi (1126x910px). This is actually a "100% crop" of the FA* 400mm image, and here there is in fact a visible difference between the two lenses:

DA 560 mm FA* 400 mm

Is a cropped image from a high quality 400 mm lens as good as the image from the 560 mm lens? No, not unless you're sticking to small prints or web files. Since you will probably use this kind of lens for birding and the like, you will already have to crop to get close enough to that evasive bird, so then there isn't really any room for a second crop when using a focal length that's "too short"!

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