Whenever a new pancake lens arrives in the lab, I’m getting pretty excited. Sure, their on-paper specs are never impressive – especially in terms of speed – but they are cute or, in other words, darn compact and super-lightweight and thus easy to carry around. So when Viltrox asked me whether I’d like to review this new -full-format- Viltrox AF 28mm f/4.5 VCM, I raised my hand, of course.
However, while this appears to be a “normal” pancake lens, this isn’t really the case here. Thus, let’s get the elephant out of the room here—this lens offers autofocus and electronic coupling, but it also has a fixed aperture. f/4.5 it is. No more, no less. If you didn’t know it, I’m sure you’ve raised eyebrows now.
At the time of writing this review, Viltrox has started a crowdfunding campaign through which you can purchase/support it for $99 USD minus a discount if you decide to order one early on. If you want to snatch an early deal, go to https://www.indiegogo.com/projects/viltrox-af-28mm-f4-5-fe-chips-size-ultra-thin-lens#/
The build quality of the Viltrox AF 28mm f/4.5 VCM is fine although you can feel that it was made to a budget. It does, however, feature a metal mount, whereas the tiny lens body is made of plastic. If you look closely at the product image above, you notice that the fixed aperture isn’t circular – which can be beneficial when it comes to the rendering of sun stars. Another oddity besides the lack of a (changeable) aperture is the lack of a focus ring – AF is all that you’ve got here. The threaded part on the barrel is only meant to support you with the mounting/unmounting of the lens.
Despite the tiny size, Viltrox managed to add a sliding lens cap that you can engage via a lever. The lever doesn’t feel super sturdy, but it does the job. As you may imagine, a lens hood is not provided because it somewhat contradicts the concept of a pancake lens. There’s also no filter thread.
A more surprising aspect is the implementation of autofocus. It’s not just a relatively cheap stepping motor but a more precise VCM (Voice Coil Motor). Typical for most pancake lenses, the AF uses an extension system to shift the “whole” optics for focusing. This works nicely, and it’s quite fast and silent.
| Specifications | |
|---|---|
| Optical construction | 6 elements in 6 groups (2x ED, 2x aspherical) |
| Number of aperture blades | Fixed (7 edges) |
| min. focus distance | 0.32m (max. magnification 1:9.1) |
| Dimensions | φ60.3 × 15.3mm |
| Weight | 60g |
| Filter size | – |
| Hood | – |
| Other features | Lens cap slider |
Distortions
Let’s start with something positive—image distortions. Unlike the Japanese manufacturers, Viltrox is (almost) fully correcting its lenses (to date, at least), so image auto-correction isn’t necessary. This is good because distortion correction is a lossy procedure. The 28mm f/4.5 has a slightly wavy distortion, which Imatest identified as pincushion distortion – which you can debate or not. In any case – it’s not much.
Vignetting
The vignetting is quite heavy in RAW images with a light falloff of 2.8 EV (f-stops). Surprisingly, Viltrox walked the extra mile here and implemented a correction profile, which cuts this down by almost 50%.
Stopping down is not supported – as mentioned – so that’s a short chapter here.
MTF (resolution) at 42 megapixels
The resolution characteristic of the VIltrox lens is mixed on a high-resolution sensor. The broader center performance is surprisingly high, with excellent results in the dead center and still very good quality near the center. However, there’s a sharp drop beyond. The border quality is much lower, and the extreme corners are soft. It’s a bit of a pity that you can’t stop down the lens here – because it would certainly be much sharper at f/8.
The centering quality of the tested sample wasn’t great. A better sample could have produced higher results.
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) 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 are reasonably well managed at the image borders, but they do increase in the image corners. A good RAW converter should be able to handle this, though.
Sample Images
The Viltrox AF 28mm f/4.5 VCM is an interesting interpretation of the pancake lens theme. Performance-wise, it's not great on a high-resolution sensor. The broader center quality is actually pretty good, but the borders aren't overly impressive and the corners are soft (and our sample was a bit uneven). Image distortions are surprisingly low, whereas vignetting does benefit from auto-correction. Lateral CAs are quite high in the image corners as well. While not aligned to shallow depth-of-field photography, the technical quality of the bokeh is Ok for a wide-angle lens. Veiling glare can be an issue in certain scenes.
The build quality is generally good. Surprisingly there's a metal mount and the quality of the plastic for the body is decent. The tiny built-in lens cap mechanism feels a bit flimsy but it's good to have it on board. Other than that, there isn't much to report here. There are no buttons nor control rings on the lens. The AF is quite fast and silent. Manual focusing is not supported.
The biggest question is probably for which user groups is targeted here. A fixed aperture of f/4.5 is quite exotic for an 28mm lens. It's certainly not meant for landscape photographers because at f/4.5 the foreground just won't be sharp in infinity focus scenes. If you want high corner-to-corner quality, it's also not for you. There are, however, a couple of scenarios where this lens could make sense. Using it with a small Sony camera on a drone comes to mind. 4K video is just about 8 megapixels and the Viltrox lens can do that. If you are looking for a lightweight lens for "talking & walking head"-style YouTube videos could be another one. f/4.5 won't matter much here. And, of course, street and social photography, where you tend to shoot quickly just to capture the moment - "Lomography" is a thing out there for many enthusiasts. In conclusion - make sure that the Viltrox AF 28mm f/4.5 VCM fits your shooting style.
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Optical Quality
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Build Quality
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Price / Performance