Samsung 20-50mm f/3.5-5.6 i-Function
On paper, a lens with only a 2.5x zoom range and a small f/3.5 to f/5.6 aperture looks pretty questionable, but this is essentially a pancake zoom. So how well does this compact zoom perform?
The lens is typical kit lens build quality. It has a plastic mount held on with only 3 screws, a zoom ring, an i-Function ring, and a locking mechanism that locks the barrel out when it is extended. To retract the barrel you have to set the lens at 20mm and slide the locking switch at the same time you turn the zoom ring passed 20mm and the lens retracts. To open you only have to twist the zoom ring back to 20mm. There is one piece of metal on the lens, and that is the short barrel that extends when you open up the lens.
A note I have to make, uncommon as it is with current lenses, the front filter ring turns when you change focus, meaning it is more difficult to use polarizers or other direction oriented filters, and is 40.5mm, which is a bit of an awkward size. I wish it would have been the same size as the primes at 43mm (the difference is very small, easy to mistake lens capes, etc).
The lens has 9 elements in 8 groups, including 1 ED element. The lens also has a 7 bladed diaphragm, as most Samsung lenses seem to have. The minimum focus distance is 0.28 m (11″), and weighs next to nothing at only 119 g (4.2 oz).
Samsung uses in camera correction by design with their lenses. What this means is they intentionally don’t correct all the distortion, vignetting, and lateral CA of the lens and correct it in software. The RAW file is left alone by Lightroom at this time. I shoot the chart using RAW + JPEG, and use the JPEG for the “corrected” results and the RAW for the uncorrected. JPEG settings are camera default.
Comments on the Optics
I notice that distortion is only corrected for the extreme barrel distortion at wide angles. I notice the upper focal lengths do not appear corrected. In the corrected files, the resolution drops slightly in the corners (even given the added sharpening in JPEG), but center performance improves. As the corners are stretched out to correct the distortion, the resolution should drop some.
Overall, corrected or not, the lens produces great results at all apertures and settings. Almost all aperture settings perform equivalently, and there is really not much to fault with this lens.
Lateral chromatic aberrations are well controlled, flare is excellently controlled, the borders don’t perform that much worse than the center for the class of lens.
Pros and Cons
- Very Good Optics
- Compact Size
- Flare Resistance
- Filter Threads Rotate
- No Image Stabilization
- Odd Filter Size