Here is the Canon RF 16mm f/2.8 STM

[gruhl28]

Just watched Gordon Laing's review:

Interestingly, the RF 16mm f2.8 and the RF 14-35 f/4 have the same problem with soft corners that don't sharpen up with smaller apertures, both being software-corrected, while the RF 15-35mm f/2.8 has optically sharper corners.

What was surprising though in the review was that the corners of the RF 16mm f2.8 were slightly sharper than those of the RF 14-35 f/4. Is this a case of prime vs zoom, with slightly better prime results when both use software corrected corners?

What struck me about the review was that he said the corners of the 16mm improved upon stopping down, which contradicts other results. Although I can't say that I saw much of a difference apart from vignetting getting better, but maybe the resolution of the video limited how much I could see. I was also surprised that the 14-35 didn't look significantly better than the 16mm, which also contradicts other results that have shown the 14-35 to be very good in the corners even with the distortion correction. My tentative conclusion (hope) is that perhaps the 16mm is better in the corners at longer distances than close up. See my comment and Neuro's reply in the 14-35 thread about this: https://www.canonrumors.com/forum/t...tortion-correction-testing.41022/#post-917468

 

[LogicExtremist]

What struck me about the review was that he said the corners of the 16mm improved upon stopping down, which contradicts other results. Although I can't say that I saw much of a difference apart from vignetting getting better, but maybe the resolution of the video limited how much I could see. I was also surprised that the 14-35 didn't look significantly better than the 16mm, which also contradicts other results that have shown the 14-35 to be very good in the corners even with the distortion correction. My tentative conclusion (hope) is that perhaps the 16mm is better in the corners at longer distances than close up. See my comment and Neuro's reply in the 14-35 thread about this: https://www.canonrumors.com/forum/threads/rf-14-35mm-f-4l-is-–-distortion-correction-testing.41022/#post-917468

Agreed, it appears that the corners do look better at longer distances on the RF 16mm, and Neuro's testing at longer distances was very insightful, and simulated real-world use more accurately.

When Gordon stopped down the lenses in the review, the corner sharpness increase was very slight, not in the order of magnitude that you normally see on other RF lenses in the same tier such as the budget RF 35 and RF 50.

 

[AlanF]

My RF 16mm f/2.8 arrived today from Canon. I recall @neuroanatomist posting that DxO PL5 gives a significantly wider field of view from RAW than the jpeg out of camera with the 14-35. I found the same with just the couple of shots taken today, with the central section of the image from RAW occupying fewer pixels width. I'll check it out tomorrow taking images of a brick wall to see if there is more distortion with PL5.

 

[tron]

I trust your results Alan. They will give us useful info just like with your telephoto lenses. The next thing is maybe a comparison with your 16-35 f/4L IS (If I recall correctly you have one) to see if the field of view of 16mm after correction is comparable.

 

[AlanF]

@tron I did the tests in a 15 minute break in the rain taking photos of a brick wall at 0.8m distance, using the R6 with either the RF 16mm or the EF 16-35mm f/4 with adapter. Each shot was taken as a jpg and RAW, and the RAW processed using DxO PL5 and its lens correction profiles.

RF 16mm
Out of camera jpg had the bricks 1.093x larger than those processed as RAW. Interestingly, whereas the ooc jpgs are the standard 3648x5472px, the processed RAW are 3648x5981px, which is a factor of 1.093 wider. So, if the 16mm ooc jpgs are truly 16mm focal length, the focal length from RAW corresponds to 14.6mm

EF 16mm
The ooc jpgs were distorted, showing any in-camera correction isn't good, or non-existent. The processed RAW gave bricks 1.074x the size of those from the ooc jpgs from the RF 16mm. This corresponds to a minimum focal length of the zoom of 17.2mm.

So, it seems like @neuroanatomist found with the RF 14-35mm, Canon's internal correction of the horrible barrel distortion works by cropping the extremes of the barrel before or after corrections, whereas the DxO PL5 uses a wider field. The extreme corners from DxO are mushy, but the areas on the RAW corresponding to the extreme corners of out of camera jpegs were as good if not better.

Checked it out at 22cm and 19m, and the results are the same, 9% larger field of view from RAW.

Edit: calculated the focal length directly from image size and it's ~14.4mm for RAW processed image, and ~15.8mm for out of camera jpegs.

 

[tron]

Many Thanks Alan. Detailed analysis as always. It looks like RF16mm is a great value for money and a very decent (after PP) UWA lens.