Coma test for the RF 24mm f1.4L

[KirkD]

I received my RF24mm f1.4L two days ago but it has been heavily overcast ever since except for a few minutes this evening. I ran outside and quickly took a few shots before the clouds completely covered up the sky. I was mainly interested in testing for coma because my main use will be nightscapes. Here is a shot. The stars in the upper right-hand corner are semi-distorted by the twigs in the Oak tree, but the stars in the upper left-hand corner were not interfered with. The shot was 10 seconds at f1.4 and ISO 400. I'm not 100% sure I had infinity focus perfect, but the clouds were moving in fast. The first photo shows the full, uncropped image. The second shows only the extreme upper left corner (about 1/8 of the vertical). I can't see any noticeable coma in the magnified image. I imagine others have been able to do a better test than this so please post your test. The weather is not supposed to clear up for another few days. Then I'll be able to take my time and get some nice night sky photos.

 

[docsmith]

This is a lens I am watching as a potential nightscape lens. So, this test is much appreciated. Keep posting.

 

[KirkD]

So here is an update on my coma testing for my new RF 24mm f1.4L. I had a nice clear night yesterday and took some photos of the night sky where the entire photo was filled with stars. I then checked the stars in each corner (the lens was shot wide open at f1.4). All four corners showed virtually no coma at all. I've posted a photo below of one of the corners (all four corners showed no coma). To give you a perspective on the magnification, my hi-res display of the entire photo is 13.75" vertical. The corner was zoomed in such that 2.125" was expanded to 13.75. This gives an equivalent print for the whole uncropped photo of 87" x 132" (7.25 feet tall by 11 feet wide). Even at that magnification, I could only see the smallest possible suggestion of any coma at all. Here is the photo of the zoomed-in corner. Obviously, the attached photo is much smaller than it appears on my full screen, but you can download the corner photo at this link here. My conclusion is that at least the particular production sample that I own, shows virtually no coma at all anywhere in the photo, including the corners.

 

[neuroanatomist]

Thanks for sharing your results!

 

[john1970]

A second thank you for sharing the results. I was really hoping that this lenses would do well with coma since I purchased it for low-light landscapes / nightscapes.

 

[KirkD]

A second thank you for sharing the results. I was really hoping that this lenses would do well with coma since I purchased it for low-light landscapes / nightscapes.

Yes. It appears to be absolutely outstanding. I'm very pleased. I don't plan to make any 7 feet x 11 feet prints to hang on the wall, but it is good to know I could if I wanted. I should mention that the testing was done with a R5 Mk II.

 

[neuroanatomist]

I had not planned to purchase the 24/1.4 VCM, but I may revisit that decision. I don’t shoot astro very often, but this seems like an ideal lens for those occasions when I do.

 

[chrysoberyl]

KirkD, thank you for these tests! The results do look good. I wonder whether there is a forced, in-camera correction. It would be interesting to see this test repeated with an earlier camera, a R6, for instance.

 

[KirkD]

KirkD, thank you for these tests! The results do look good. I wonder whether there is a forced, in-camera correction. It would be interesting to see this test repeated with an earlier camera, a R6, for instance.

That is a good question. I don't have another camera to test this lens on. My understanding is that there is in-camera correction for distortion. I'm doubtful that it corrects for something like coma, but I think it is a good idea to test this lens on a different camera just to verify.

 

[KirkD]

I see that the Digital Picture has tested the lens for coma and provided a photo of the results. His results are not as good as my particular lens, although he still describes the results as follows ... "While the stars have a little tail, the stars are tiny, and the overall performance is quite good for this focal length." My particular lens has virtually no coma at all, whereas his has some. This suggests that there may be some variation between lenses, so I hope that my results do not mislead anyone into thinking that all examples will be equally as good.

 

[docsmith]

My RF 24 f/1.4 VCM arrived earlier today. While not one of the lenses at the top of my list, I have always wanted something like this for nightscapes and I do love the 24 mm focal length. I recall evaluating and almost buying the Zeiss 25 f/2, Sigma 24 f/1.4, and the Canon EF 24 f/1.4, of course.

After seeing this thread, reading Bryan's review and having a report of potential auroras Tuesday night put me over the edge.

My coma test:
Top Left (1/9th of frame) at f/1.4, 15 sec, ISO 400, R1


Top Right at 4 sec, f/2, 4 sec, ISO 1600 R1


For fun, this is R1, 15 sec, f/2, ISO 200. Jupiter (and moons?) and Pleiades

I am seeing some start to trailing at 15 secs, but the coma seems exceptionally well controlled. In the image below, I might see some, but I am not seeing it in other images, so I think that is something else.

A different composition, but here is an entire scene with the profile in LRc turned on (R1, 3.2 sec, f/1.4, ISO 400)


Same image with the profile turned off:

Profile turned off +2 stops exposure so you can see what is happening better:

Canon is doing a lot to this image to get the final picture.

 

[nhandumuc]

Thanks for all the great tests. Could you guys please if possible do these tests for 35VCM and 50VCM, I’m on the fence getting these lenses for night panorama!