|
Meike AF 85mm f/1.8 STM - Review / Test Report - Analysis |
|
Lens Reviews -
Sony Alpha (Full Format)
|
|
Page 2 of 3
Distortion
The Meike AF 85mm f/1.8 STM produces a mild pincushion distortion of ~0.4% both in RAW mode and JPEG mode. As mentioned, a correction profile hasn't been implemented (yet). Hopefully, that's something that will be added via a future firmware update.
Vignetting
Ultra-fast lenses tend to have a very high vignetting at large-aperture settings. However, the Meike lens is pretty well corrected in this respect. At f/1.8, the light falloff is at 1.6EV (f-stops) - while clearly visible, this is lower than on Sony's own FE 85mm f/1.8 (in RAW mode). Stopping down gradually reduces the issue, and it's no longer relevant from f/4 onward.
MTF (resolution)
The Meike AF 85mm f/1.8 STM has a pretty decent resolution characteristic. The center and also the near-center quality are sharp straight from f/1.8. The quality drops substantially towards the borders/corners which are only on a mediocre level at this setting. The contrast level is also reduced. Stopping down to f/2.2 doesn't change much but there is a visible improvement beyond. The outer image field reaches good results at f/2.8 and the overall peak is reached around the f/5.6 mark with very good quality across the image field. Diffraction effects are a limiting factor from f/11 onward.
The field curvature is low. The centering quality of the tested sample was good.
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 of sharpness.
If you want to know more about the MTF50 figures, you may check out the corresponding Imatest Explanations
Chromatic Aberrations (CAs)
Lateral CAs vary along the aperture range. They are slight at large apertures and decrease to negligible levels from f/4 onward.
Bokeh
A fast prime lens is nothing without a good bokeh, and this is clearly a strength of the Meike lens. Out-of-focus highlights have a silky smooth inner disc with just a tad of outlining at the edges of the discs. The circular shape starts to deteriorate with the more edgy aperture shape when stopping down.
The circular shape is maintained in a very broad zone at f/1.8. As usual, they deteriorate in the corners. Strangely, these outer "discs" have a somewhat irregular shape. This also applies to f/2.2. At f/2.8, the outer discs have been mostly restored.
The quality of the general blur is very smooth in the image background (shown to the left below). The less important foreground is clearly rougher in comparison.
Bokeh Fringing / LoCA
Boheh fringing (sometimes referred to as LoCA) is an axial color fringing effect with purplish halos in front of the focus point and greenish beyond.
And, unfortunately, this is a major weakness of the Meike lens. As you may see yourself, the fringing is pretty dramatic at f/1.8 and f/2.2.
The issue is reduced at f/2.8 and moderate at f/4.
You may also notice a focus shift (Residual Spherical Aberrations) towards the rear when scrolling through the aperture range below (the focus distance was held constant).
|
