Earlier this month I discussed my preliminary experiment with the Nikkor-P 1200mm f/11 lens on a Canon EOS 5D using a third-party adapter. Though the first test was a success, the conditions under which I took my first photographs of the moon with this combination were less than ideal. High humidity and intermittent cloud cover from our annual monsoon season in Tucson affected the clarity of the images, and I was left to wonder what the results would be under better conditions. Also, the last experiment left me wondering if I could take the test one step further and throw my Canon EF 2X II extender into the mix to get an effective 2400mm combination to work.
The weather has dried out quite a bit this week in Tucson, so I thought this would be a good time to revisit the experiment. I began last night with the setup I had on the first experiment: The Nikkor-P 1200mm lens was attached to the Canon EOS 5D by means of a consumer-grade adapter from Fotodiox. Mirror lockup and a cable release was used on all shots, and all exposures were fully manual. I took some shots at 1200mm, f/16, 160/sec @ ISO 1600. Note: The only reason I shot at ISO 1600 was because I have a bad habit of forgetting to check my settings before I shoot and I had left it at that setting a few days earlier – never mind they didn’t sound right at the time. Oh well…I was shooting at dusk, so it didn’t register. Anyway…for comparison, I also took some shots at 200mm, using a Canon EF-70-200mm f/2.8L USM lens at f/16, 1/160 sec, ISO 1600.
The next step was to slap on the 2X extender between the adapter and the camera. When I looked through the viewfinder, I was thrilled to see that the moon filled up the frame on the short side, and I let my daughter fire off a couple of shots at the same settings I had used just moments earlier. I checked the viewfinder to review these last shots and something was clearly wrong: The moon didn’t fill the frame as it had in the viewfinder. I took a few more shots and checked again, but the result was the same. Next, I checked the counter and realized that the images were not being recorded. It didn’t make sense because the shutter was obviously being tripped. I removed the extender, reconnected the camera to the lens, and everything worked fine again. Obviously, this had something to do with the extender, which was a huge disappointment after getting a glimpse of what was possible through the viewfinder. I was running out of time; I had a narrow window of opportunity to get the shot from my back yard and I didn’t want to haul everything to another location without knowing if I could get things to work, so I shelved the project for the night.
Tonight, I got online and did some research on third-party extenders; I seemed to remember that the Kenko and Tamron adapters would allow the use of lenses outside of Canon’s compatibility list. Everything I read pointed to the fact that this might be a problem with the Canon extender trying to communicate the lens spec to the camera. I found an obscure reference to a similar issue in a forum post in which the poster suggested that if the extender was attached but turned just shy of the contact points meeting between the extender and the camera, the extender could be used with other “non-compatible” lenses. I tried that with just the camera and extender – no lens – and sure enough, an image recorded. I don’t feel comfortable with the idea of not having the extender attached securely to the camera, so I tried another trick that I’ve read about: covering the contacts with tape. I covered the contact points on the extender with painters’ masking tape and trimmed off the excess before carefully reconnecting the extender to the body of the camera. Another test shot and again, the image was recorded. [Note: I’ll try to take a photo of the extender with the contact points covered within the next couple of days].
With that problem solved it was clear that I’d be able to get the lens/adapter/extender/camera combo to work. The following images show the results. The first two photographs were taken last night, while the one on the right was taken this evening with the lens/adapter/extender/camera combo yielding an effective 2400mm focal length.
Below is a full-sized crop from the last image. Note: All of these images were processed with Capture One 4.8.1 with adjustments only to exposure. Sharpening was done at the default settings in Capture One and no sharpening was done later in Photoshop.
Certainly the image could be sharper, but there’s no way I could get close to this amount of detail without using the extender. Believe it or not, some of the lack of sharpness could be due to the motion of the moon itself. Remarkably, at this focal length it is actually possible to see the moon track across the frame in the viewfinder and I’m fairly sure that at 1/15 sec some of that motion, however slight, must affect the image. Perhaps on another night I’ll try again at various shutter speed/aperture/ISO combinations to try to find the sweet spot. In the mean time, I can happily declare this experiment a success.