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Canon R5 Mirrorless Camera Tested for Astrophotography 

The R5 is a stock camera, not filter-modified. Auto-guided with the Lacerta MGEN3 guider. Stacked, aligned and blended with Photoshop. Taken May 22, 2022, with the sky brightening with dawn twilight toward the end of the set. No filters were employed. Credit: Alan Dyer

I put the 45-megapixel Canon R5 mirrorless camera through its paces for astrophotography. 

A high-resolution (in this case 45-megapixel) stock camera doesn’t seem like it would be the first choice, or even a good choice, for astrophotography. A lower resolution camera like the 20-megapixel Canon R6 I reviewed in 2021 for AGT, with its larger pixels, is usually considered the better choice for astrophoto use, due to the lower noise. 

However, for nightscapes and for deep-sky images shot with short-focal length telescopes, high resolution is attractive, to provide the sharpest detail. But is the added resolution worth the cost of higher noise? And, indeed, the cost period, as the Canon R5, like all high-megapixel cameras, does not come cheap.

I tested the Canon R5 against the 20-megapixel Canon R6 and the 30-megapixel Canon Ra, the astronomical variant of Canon’s original mirrorless camera, the EOS R.

The Canon R5 has a full-frame sensor with 45 megapixels, producing images 8192 by 5464 pixels in size, and making 8K videos possible. Credit: Alan Dyer

Noise Performance — Nightscapes

The key camera characteristic for astrophoto use is noise. There is no point having lots of resolution if, at the high ISOs we use for most astrophotography, any added detail is lost in noise. But I was pleasantly surprised that proved not to be the case with the R5.

As I show below, noise is well controlled, making the R5 usable for nightscapes at ISOs up to 3200, if not 6400 if needed in a pinch.

This shows the noise on a dark nightscape at the typical ISOs used for such scenes. Noise reduction at the level shown has been applied in Adobe Camera Raw. Credit: Alan Dyer

With 45 megapixels, at the upper end of what cameras offer today (some models have 60-megapixel sensors), the R5 has individual pixels that are each 4.4 microns in size, the “pixel pitch.”

By comparison, the 30-megapixel Canon R (and Ra) has a pixel pitch of 5.4 microns, while the 20-megapixel Canon R6’s pixel pitch is a generous 6.6 microns.

The bigger the pixels (i.e., the larger the pixel pitch), the more photons each pixel can collect in a given amount of time – and the more photons they can collect, period, before they overfill and clip highlights. More photons equals more signal, and therefore a better signal-to-noise ratio, while the greater “full-well depth” yields higher dynamic range.

This compares the R5 to the R6 and Ra cameras at the high ISOs of 3200 and 6400 often used for dark Milky Way nightscapes. Credit: Alan Dyer

In nightscapes, the R5 did show more noise at high ISOs, especially at ISO 6400, than the R6 and Ra, but the difference was not large, perhaps one stop at most, if that.

This compares the R5 to the R6 and Ra cameras at the more moderate ISOs of 800 and 1600 used for brighter nightscapes. Credit: Alan Dyer

At slower ISOs the R5 showed a similar level of noise as the R6 and Ra, but a finer-grained noise than the R6, in keeping with the R5’s smaller pixels. In this test set, the R5 did not exhibit noticeably more noise than the other two cameras. So, if kept to ISOs of 3200 or lower, the R5 can produce superb results. 

This shows noise in frame grabs of aurora movies shot the same night with the R5 at 8K, and 4K with the Canon R6 at 4K, all at ISO 51,200. Credit: Alan Dyer

Where the noise difference between the R5 and R6 is more marked is when shooting low-light videos, such as of the Northern Lights. The R6 can be used quite well for movies at ISO speeds as high as 51,200 or 64,000. The R5’s top ISO in movie mode is 51,200 and appears much noisier than the R6 at that speed. I would not recommend the R5 for low-light video.

You can view a video of an aurora display showing the noise difference here on Vimeo

Noise Performance — Deep Sky

Here I test the R5 for shooting demanding long exposures of deep-sky objects through telescopes. The test shots are all single frames, not stacked blends of multiple exposures.

This shows the R5 at the typical ISO settings used for deep-sky imaging, with no noise reduction applied. The inset shows the portion of the frame contained in the blow-ups. Credit: Alan Dyer

On deep-sky exposures through a telescope, above, the R5 again showed quite usable images up to ISO 1600 and 3200, with ISO 6400 a little too noisy, in my opinion, unless a lot of noise reduction was applied or many images were shot to stack later.  

This compares the R5 to the R6 and Ra cameras at ISO 6400, higher than typically used for deep-sky imaging. No noise reduction was applied to the raw files. Credit: Alan Dyer

As with the nightscape set, at high ISOs, such as at ISO 6400, the R5 did show more noise than the R6 and Ra, as well as more colour splotchiness in the dark sky, and lower contrast. The lower dynamic range of the R5’s smaller pixels is evident. 

This compares the R5 to the R6 and Ra cameras at the lower ISOs of 800 and 1600 best for deep-sky imaging, for better dynamic range. No noise reduction was applied to the raw files. Credit: Alan Dyer

At lower ISOs the difference among the three cameras was not so obvious, with the R5 performing quite well against the lower megapixel cameras. The R5 will be suitable for shooting and resolving small, bright targets such as globular clusters and planetary nebulas. 

Resolution — Nightscapes 

 

This compares blow-ups of the nightscape scene shown earlier, showing the sharper details in the tree branches with the increasing resolution of the R5 over the Ra and especially the R6. Credit: Alan Dyer

Nightscapes, and indeed all landscape photos by day or night, are where you will see the benefit of more megapixels. Finer details in the foreground show up better. Images are less pixelated. In test images with all three EOS R-series cameras, the R5 did provide sharper images to be sure. But you do have to zoom in a lot to appreciate the improvement. 

But if making and selling large prints is your desire, the R5 will prove its worth. 

Resolution — Deep Sky

On starfields, the difference is not so marked. However, in comparing the three cameras below, with images taken at a focal length of 420mm, the R5 did provide sharper stars, with faint stars better recorded, and with less blockiness (i.e., “square stars”) on all the star images. 

At that focal length the plate scale with the R5 is 2.1 arc seconds per pixel. With the R6 it is 3.2 arc seconds per pixel.

This compares extreme blow-ups of images of the North America Nebula used for the other tests, shot with a 94mm f/4.5 refractor with the three cameras. Credit: Alan Dyer

I haven’t shown it here, but the R5 also proved excellent for lunar imaging, recording noticeably more detail at any given focal length than the other cameras. 

Red Sensitivity 

The R5 I bought was a stock “off-the-shelf” model. It is Canon’s now-discontinued EOS Ra that was “filter-modified” to record a greater level of the deep-red Hydrogen-alpha wavelength from emission nebulae in the Milky Way. 

As I show below, compared to the Ra, the R5 did well, but could not record the depth of nebulosity the Ra can, which is to be expected from a stock camera. 

This compares identically processed single four-minute exposures at ISO 800 with the R5 vs. the red-sensitive Ra. Credit: Alan Dyer

Amp Glows and Thermal Noise

I was pleased to see the R5 did not exhibit any annoying “amp glows” — dim, often magenta glows at the edge of the frame in long exposures, created by heat emitted from sensor electronics that adding infrared glows to the image. 

I saw noticeable amp glows in the Canon R6 that could be eliminated only by taking dark frames or using Long Exposure Noise Reduction (LENR). 

With a lack of amp glows, the R5 should work well when filter-modified to record either more visible Hydrogen-alpha red light, or deeper farther into the infrared spectrum.

This shows a long-exposure nightscape scene both without and with Long Exposure Noise Reduction turned on. LENR eliminated most, though not all, of the hot pixels in the shadows. Credit: Alan Dyer

I did find that in long exposures at high ISOs, such as for the dark ground in nightscapes, the R5 was prone to lots of hot and colorful pixels, especially on warm nights. These thermal noise hot pixels can be eliminated by turning on LENR, at the cost of taking twice as long to acquire images. 

Other Features

On mild nights, I found the R5 ran fine on one battery for the 3 to 4 hours needed to shoot a time-lapse sequence, or a set of deep-sky images, with power to spare.

When manually focusing using the rear screen, you can zoom in by 6x or 15x to aid in precise focusing. These are magnification levels higher than the 5x and 10x of most other Canon cameras, great for ensuring images are sharp and, showing off the R5’s high resolution.

Canon Top Screen – The R5’s top-mounted information screen. Credit: Alan Dyer

The R5, like the original R, has a top backlit LCD screen for display of current camera settings, battery level and Bulb timer. The lack of a top screen was one of my criticisms of the R6.

The R5’s front-mounted N3-style remote port. Credit: Alan Dyer

The R5’s remote shutter port, used for connecting external intervalometers or time-lapse motion controllers, is Canon’s professional-grade three-pronged N3 connector. It’s sturdier than the 2.5mm mini-phono plug used by the Rp, R and R6. it’s a plus for the R5. 

Conclusion

Yes, at $3,899, the R5 is costly. However, it proved to be surprisingly low in noise, and has worked very well for both nightscape and deep-sky photography, where its high resolution does produce a noticeable improvement in image detail.

To make use of the R5’s resolution, you do have to match it with sharp, high-quality optics (such as the Canon RF zoom lenses I tested here for AGT). The R5 can be just the start of a costly spending spree! 

 

PLUS

High resolution sensor with relatively low noise

Top LCD information screen missing in the Canon R6

Higher 6x and 15x magnifications for precise manual focusing

Pro-grade Type N3 remote port

 

MINUS

Noise is higher than the Canon R6, especially in movies

Exhibits thermal-noise hot pixels in shadows

High cost

 

MSRP: $3,899
Website: https://www.usa.canon.com/internet/portal/us

 

NOTE: An even more detailed review of the Canon R5 for astrophotography, including tests of ISO invariancy, its use for lunar photography, and for 4K and 8K movie shooting, can be found at the author’s AmazingSky blog site.

 

About Alan Dyer

Alan Dyer is an astrophotographer and astronomy author based in Alberta, Canada. His website at www.amazingsky.com has galleries of his images, plus links to his product review blog posts, video tutorials, and ebooks on astrophotography.

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