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Laowa Argus 33mm f/0.95 CF APO - Review / Lens Test - Analysis |
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Lens Reviews -
Sony Alpha/NEX (APS-C)
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Page 2 of 3
Distortion
The Laowa Argus 33mm f/0.95 CF APO can't take advantage of auto-correction thus it has to rely on its original capabilities. Most Laowa lenses don't have issues with distortions and the Argus is no exception in this respect. At just ~0.27%, they aren't really noticeable in real life.
Vignetting
While image distortions are negligible, the same can't be said about vignetting - although this can't come as a surprise given the ultra-large aperture. At f/0.95, the light-falloff is over 2EV (f-stops) which is very high by APS-C standards. Stopping down to f/1.4 sees a noticeable improvement but it's only well-controlled from f/4 onward.
MTF (resolution)
The ambitious optical design shows some benefits with respect to the resolution potential. The quality is pretty impressive, even at f/0.95. The broader center is on a very good level and only the corners soften without being terrible. Stopping down results in a gradual improvement along with the aperture. A significant boost occurs at f/1.4 with very good quality across the image field. The peak performance is reached around f/2.8 already. The broader center is sharp as a tack here and the outer image field stays just short of excellent quality. Diffraction impacts the quality at smaller aperture settings but this is only getting relevant beyond f/8.
The field curvature is marginal. The centering quality of the tested sample was mediocre.
Please note that the MTF results are not directly comparable across the different systems!
Below is a simplified summary of the formal findings. The chart shows line widths per picture height (LW/PH) can be taken to measure sharpness.
If you want to know more about the MTF50 figures you may check out the corresponding Imatest Explanations
Chromatic Aberrations (CAs)
The APO designation in the lens name promises very low color fringing. While we agree that lateral CAs are very low, they are still present with an average pixel width of around 0.5px at the image borders.
Bokeh
The talk about resolution etc is exciting but the main reason for investing in such a lens is shallow depth-of-field photography so let's check out the quality of the bokeh (rendering of the out-of-focus blur).
The Laowa Argus 33mm f/0.95 CF APO suffers from an unusual effect concerning out-of-focus highlights. You may notice a couple of aspects in the sample crops below. The inner zone of the discs is exceptionally smooth. So that's great. But you may also notice that there is a strange vignetting effect at the top and bottom. This is more obvious in the sample images further down below. This effect is only partially related to the lens itself, but the camera also plays a role in this.
On Sony APS-C cameras (and notably the A6300, which we used for testing here), the sensor is deeply recessed - see below. The problem is that extremely angled, out-of-focus light-rays are partially hitting the "walls" of the sensor housing, causing the top/bottom vignetting in the highlights. We verified this theory by mounting the lens on a full format Sony camera. This mechanical vignetting is NOT present in these images - simply because there is more space. Most likely, this effect is limited to all (?) Sony APS-C E mount cameras but that's nothing that we can guarantee.
The effect is gone from f/1.4 simply because the smaller aperture crops the vignetting. You may also notice that the highlights are getting more distorted to cat eyes towards the borders but this is a more common mechanical vignetting effect and corrected the more you stop down.
As far as the general blur is concerned, the results are less complicated. The blur is relatively smooth in the background (shown to the left) albeit you may spot an unsymmetrical rendering and reduced contrast. This is also present in the foreground blur which is also a bit rougher.
While this may all sound slightly negative, the issues are far less evident in real life - see the sample image section. At least in our samples, the highlight vignetting is hard to spot unless you are looking for it. Undoubtedly, this can be more obvious in scenes where these highlights are more dominant. Overall, the bokeh is still pretty pleasing because of the sheer amount of achievable out-of-focus blur, hiding some imperfections.
Bokeh Fringing (LoCA)
A "true' APO lens shouldn't just correct lateral CAs (on the focus plane) but also axial/longitudinal CAs (on the Z-axis). While Laowa has been able to do the magic in the past, the correction isn't perfect this time. Below, you may spot the purple tint in front of the focus zone and the green one beyond. This isn't dramatic and low in the grand scheme of things but it remains visible from f/0.95 to f/1.4, much less so at f/2.
As a side note, you may notice that the focus point shifts to the rear when stopping down (without changing the setting). So there's a fair amount of RSA (Residual Spherical Aberration). This is something to keep in mind at close focus distances and large apertures where you should stop down the lens PRIOR to focusing.
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