Samyang 24mm f/1.4 ED AS UMC (EOS) - Full Format Review - Analysis
Lens Reviews - Canon EOS (Full Format)

Distortion

The Samyang 24mm f/1.4 produces a medium to heavy amount of barrel distortion (~3%) and this can be visible in certain scenes - especially in architecture photography.

Vignetting

The ultra-large aperture Samyang lenses have never been moderate terms of vignetting on full format DSLRs and the 24mm f/1.4 follows this tradition. At max. aperture the light falloff is excessive and still easily visible at f/2.8. You have to stop down to at least f/4, better f/5.6 to tame the issue to a non-disturbing degree. To be fair - while this is hardly impressive it is also normal in this lens class in general - the Canon EF 24mm f/1.4 USM L II isn't any better for instance.

The following images show the vignetting at f/1.4 and f/2.8 respectively.

MTF (resolution)

The resolution of the Samyang lens is pretty impressive for a f/1.4 lens. The center resolution is very high at f/1.4 and f/2 and the outer image region is still good. However, the contrast is a bit soft at these settings so the image quality is not perceived as very sharp (sharp = high resolution + high contrast). There's a significant boost in quality at f/2.8. The center quality reaching easily excellent levels and the border region "just" makes it across the very good rating barrier here. The contrast is also very snappy from here on. The peak performance is reached between f/4 and f/8 with very impressive results across the image field. Diffraction starts to be a limiting factor from f/11 onward but you don't need to worry at this setting yet.

As mentioned the center quality of the tested sample wasn't overly stellar (drop in quality towards the left image side). The field curvature was generally moderate for such a lens.

Below is a simplified summary of the formal findings. The chart shows line widths per picture height (LW/PH) which can be taken as a measure for sharpness. If you want to know more about the MTF50 figures you may check out the corresponding Imatest Explanations

Chromatic Aberrations (CAs)

Lateral CAs (color shadows) are quite low with an average pixel width of less than ~1px at the image borders. This is a very good result in this chapter.




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