Best DSLR or ILC for Night Sky Imaging?

Started Nov 8, 2017 | Questions thread
rnclark Senior Member • Posts: 3,755
Re: Best DSLR or ILC for Night Sky Imaging?
1

kiwi2 wrote:

rnclark wrote:

Boy you guys are still at it. Don't be fooled: many things change in those dpreview comparisons. XT-2: aps-c 3.93 micron pixels, 5DII: full frame 6.4 micron pixels, 80D: aps-c 3.7 micron pixel size, a6000: aps-c 3.92 micron pixels. They change the lens between formats, and it looks like they change the focal length within formats too. They keep f-ratio constant to keep exposure the same, but that means absolute light levels change, which means photon noise levels change. Then the demosaicking algorithm changes between cameras. Small tweaks of settings in the raw converter will make huge changes in results. Or a different raw converter, like rawtherapee will make huge improvements in results.

And the noise is not representative of the noise in a night sky image, which is dominated noise from the sky.

The only real issue between camera bodies are which ones have banding issues at the ISO used for night sky photography, and dpreview does not show banding. (The ancient generation 5DII has banding issues.)

No one should be doing night sky photography at iso 12800.

The differences between cameras in short exposure night sky images as by far more affected by the lens and exposure time (e.g. 20 versus 30 seconds). The differences between modern cameras given the same lens is on the order of less than 1/3 of a stop.

Here are some 100% crops from my Canon 100D and X-T2 of the camera produced jpgs with all the default settings at ISO 6400...

To me the Fuji is far more usable at higher ISOs.

I have always used the noise comparison here at dpreview with any potential camera purchase to gauge its usability for the nightscapes I like to do. It shows me what the market has to offer at the particular moment as far as noise goes and what to avoid.

Just to be clear, the dpreview comparison above is more about the changing lenses used than the sensor. DPreview changes focal length while keeping f-ratio constant. That means lens aperture area changes between cameras, thus the light delivered to the sensor is changing, and that means the amount of photon shot noise is different due to the lens, not the sensor.

Download the images and look at the exif to see what focal lengths and f-ratios were used. The Sony 7RII is full frame, so the use the longest focal length and largest aperture area. The Olympus is a 1/1.7" sensor which means something like a 4.5x crop, so they use a focal length ~4.5x shorter. if both lenses are the same f-ratio (which they will be), then the amount of light delivered to the Olympus sensor is ~ 4.5^2 ~ 20 times less than the light delivered to the Sony sensor. To be clear: IT IS THE LENSES USED THAT MAKE THE DIFFERENCE, NOT THE SENSOR. This false internet idea of larger format sensors are more sensitive is now probably the biggest myth in photography. That is saying a lot because there are so many other competing myths.

Another big myth: ISO increases sensitivity. ISO does not change the amount of light the sensor collects.

The Canon 100D image made with a 14 mm f/5 lens has only a 14/5 = 2.8 mm diameter aperture, far smaller than a dark adapted human eye (about 7.5 mm diameter). The 14 mm f/5 collects some 7 times less light than the dark adapted human eye, and the human eye integrates 7 to 15 seconds in very low light.

Try putting a 24 mm f/1.4 (aperture 17.1 mm) on the 100D, and it will collect (17.1/2.8)^2 = 37 times more light! Want more field of view, just do a 2x2 or 3x3 mosaic and you'll end up with a far better image than you could ever do with the full frame sony (or any other recent full frame camera) with a14 mm f/5 lens, with far greater resolution, better star images and fainter detail. Want even better: use a 35 mm f/1.4 and collect 80 times more light, or a 50 mm f/1.4 and collect 170 times more light. See the pattern? The lens is the key and far far far outweighs the small differences in camera sensors.

For more information see:

http://www.clarkvision.com/articles/characteristics-of-best-cameras-and-lenses-for-nightscape-astro-photography/

http://www.clarkvision.com/articles/exposure/

Roger

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