Canon 50D – Stacked TC Moon Shots

When I got home from work yesterday after running a few errands, the moon was out in a fading sky. The tripod was still out from the AF Microadjustment processes from the night before so I toted it out to the back patio and, using live view, got a few images of the moon. I noticed a bit of atmospheric haze at the upper left (blooming from the haze of the day) so I stowed the camera for a bit and went out later to shoot some more.

I was using my 50D with the EF 100-400 f/4.5-5.6 L IS USM with the 1.4x TC stacked with the 2x TC. For those of you playing the home game, that results in 400*1.4*2*1.6 (the sensor crop factor of the 50D) to yield a 1792mm effective focal length. If you are getting really precise, the 1.4 crop factor really adds the square root of 2 which is 1.4142136 ish… so you would really get 1810mm effective focal length.

Just to see what the difference was at just 400 x 1.6 crop factor, I shot a few of those too in the second shooting of the day.

Full frame shots were processed in Lightroom 2.1 release candidate w/ no change to the noise reduction. Pic 1 is ISO 400 for 1/60th second at f/11 showing f/16 actual (the camera picks up the info from the 2x TC but seemingly ignores the info from the 1.4x TC – so stuff comes out 1 stop darker when it hits the sensor; if you look at the exif on the larger images, you’ll see focal length of 800 – ignoring the 1.4x TC and the 1.6 crop factor of the body, fyi.); Pic 2 is ISO 800 for 1/250th of a second at f/14 showing f/19.8 actual (14 x square root of 2 to add one stop); Pic 3 is also ISO 800 for 1/250th of a second at f/14 pulled back one stop to have the exposure match the previous pic. Exported from Lightroom as 800 wide jpgs with image quality of 70 (out of 100) with the option of "sharpen for screen".

The three images – as framed in the camera: (click to enlarge)

Moonnocrop1_3 Moonnocrop2_2 Moonnocrop3_2

Stacked TCs + 400 – Stacked TCs + 400 at night – 400 only at night.

Here are some 100% crop samples from all three images. Processed as above except the export was done as JPGs w/ 100 quality, imported into PhotoShop CS3, cropped to 500×333 and had the watermark placed. "Save for Web" as 70 quality JPGs:




I tried to get the crops to match as closely as possible on the two stacked TC shots; but the rotation of the moon over the few hours between the evening and night shots didn’t allow me match exactly. I didn’t want to rotate the image in Lightroom and have the re-sample do something good or bad to the image quality, so I just tried to include similar distinct features in all.

Neat stuff – looking forward to trying later in the fall/winter when the colder air will have less optical distortion on the images – I could see the sharpness wavering in Live View much like the wavering of heat on a road in the summer…

Thanks for reading!

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