Stacking comparison: Canon 80D vs. Nikon D7000

by Marko Riikonen and Petri Martikainen

One of us, Martikainen, was passing on May 25 though Joensuu where the other one, Riikonen, was staying, and we had decided to do a stacking comparison with our cameras weather allowing. It went swimmingly. There was high cloud from morning to the sun set and when we rendezvoused in the evening on a grassy field next to lake Pyhäselkä to set up tripods, cameras and blockers for the test, the display reached its peak.

Martikainen was photographing with Nikon D7000, Riikonen with Canon 80D. We both had Samyang 8 mm fisheye, though not the same model. Our blockers differed a bit. Martikainen had the blocker on a separate tripod, whereas Riikonen's was attached to the camera hot shoe.

We set identical iso, shutter speed and aperture. Then we took 136 photos every 5 seconds, at around 1/3 of the of way there was a little longer simultaneous break.

In postprocessing we harmonized the color temp and tint of raw's before turning them into 16 bit tiffs for stacking with Halostack in full size. As the 80D images are larger than D7000, the former's final stack was downsized to match the latter before we gave them identical application of the usual methods of usm, br and bgr.

Downsizing the 80D stack before the enhancements could make it lose some of its higher resolution advantage, so we made a test. Usm with a radius higher relative to the two cameras image size was applied to the 80D stack before downsizing and this was compared to the version where the 80D stack was first downsized and then usmed (with the smaller radius). There was zippo difference. So it seems ok to downsize the 80D images to D7000 scale before enhancements

The test showed D7000 as the better halo camera, something that Riikonen had suspected all along. We do not know how to characterize in proper terms the differences seen in the photo comparisons, but it seems like 80D has more problems with color noise.

Terminology:

usm = unsharp mask

br = blue minus red

gr = green minus red

bgr = background removal 

Original stack. Left 80D, right D7000

 

2 x usm (radius 25, 25)

 

3 x usm (radius 25, 25, 12.5)

 

br

 

br + bgr

gr

 

gr + bgr

 

bgr

100% detail (after D7000). Left D7000, right 80D. 2 x usm (radius 25, 25)

Double CZA, Kraków, Poland

On May 7, I was working on my programming side project. At about 17:15 local time (UTC+2h)

I was finally able to take a short break. I decided to get some fresh air on my balcony (facing south).The temperature was about 17-18°C and a substantial fraction of the visible sky was covered in rather thick clouds. The zenith area, however, was quite clear, except for a layer of nebulous cirrostratus clouds and some broken mid-level clouds. I could see a faint circumzenithal arc, so I went back inside and grabbed my camera. I took only three pictures of the CZA at 17:20, 17:21 and 17:22, before the arc disappeared completely. I noticed it was a little broader than usual, but I thought that maybe it had something to do with the solar altitude. At 18:30, I finished my work for the day and looked out of the window again. The CZA was back and I thought I could see a supralateral arc as well, so I took some more pictures. About 25 minutes later, thick clouds rolled in from the west and obscured the display. 

Since it wasn’t a particularly bright display, I didn’t think about it much until the next day when I began processing the photos I took over the last week. I was pleased to find CZA, supralateral and a suncave Parry arc (Apr 30) and another CZA + supralateral display (May 6), and then began to process the few photos that I’d taken on the previous day. The first one showed just a normal CZA, but in the second one I could see a faint rainbow smudge right under the CZA. At first, two things came to my mind: 46° halo and camera artifacts. Stellarium told me that the sun altitude was 25°. According to a chart I found on the internet, at this solar altitude the CZA should be quite narrow and the 46° halo should touch the CZA. Also, the arc in my pictures followed the shape of the CZA instead of curving downwards. I could see it in the third picture (taken in a slightly different direction) too, so I thought I could safely assume it was not an artifact or a lens flare. The rest of the photos I took later in the evening revealed a regular CZA, supralateral arc and a 46° halo – they looked completely different to the weird double arc. Then I remembered reading about an unusual type of halo related to the CZA before, but I couldn’t remember where, so I submitted my report to spaceweather.com in hope of it getting some attention there.

Meanwhile, I went on looking for the mysterious CZA phenomenon I read about earlier. I stumbled upon it a few days later, by accident. Someone had posted a link to a Halo Vault article on reddit describing a secondary CZA spotted in China. Then I found the report of A.F. Jensen. I was really excited when I realized that the second report fitted my observation quite well, so I decided to write you immediately. 

Lately, halos have been keeping my quite busy. I could see another CZA / supralateral / suncave Parry arc combo in the morning of May 14 and there is a nice 22° halo visible right now. Honestly, I can’t remember seeing that many displays in a row since I’ve seen my first one in May 2005!

                                                                                                                                         - Tomasz Adam