Best DSLR or ILC for Night Sky Imaging?

Started Nov 8, 2017 | Questions thread
OP landscaper1 Veteran Member • Posts: 3,488
Re: Best DSLR or ILC for Night Sky Imaging?

rnclark wrote:

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:


At what point, Roger, does one conclude that one is talking to a wall?  I'm continually amused and bemused when I read that some people are so wedded to what they've already purchased that they cannot bring themselves to admit that it wasn't all that they imagined it would be.

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