Lens pentax fa 31mm f1.8 al limited đánh giá năm 2024

The Pentax company hasn’t decided yet to launch digital cameras with a full frame detector and it is quite consequential in offering bodies with APS-C/DX format sensors. What’s more, their policy is professional and well thought out. The bodies are rather small and solid, often offering such possibilities which are non-existent in rival cameras offered at the same price point. If we add a series of limited lenses – small but solidly build – we get a system which differs noticeably from others, currently available on the market.

If you have a system based on a detector smaller than full frame you can offer lenses which are not so big but remain fast and very good optically. It is perhaps not easy but certainly possible as it was proven by testing say, Olympus lenses. Pentax has chosen a different way, giving its users lenses which are small but not exactly fast. If you develop a system based on “primes” it would be difficult to run away constantly from the necessity of offering a good standard lens as well which, in the case of Pentax, should have a focal length in the range of 30-35 mm.

At first glance we are spoilt for choice. You can start the list by the Pentax smc DA 35 mm f/2.4 AL, the youngest device on the market but offered for a good price and providing good image quality as well. It would be difficult to call it solidly build and fast, though. The build quality of the Pentax smc DA 35�mm f/2.8 Macro Limited is much better but that lens is even slower and certainly not cheap. Even several years ago you could buy the full frame Pentax smc FA 35 mm f/2 AL and the price tag was quite reasonable. After the launch of the Pentax smc DA 35 mm f/2.4 AL, though, these lenses started to disappear from the shelves and the price of new and second-hand specimens of that model raised very sharply.

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The fastest lens which can be considered a standard is the Pentax smc FA 31 MM F/1.8 AL. It is quite an elderly construction, designed during the era when analogue photography reigned supreme. Still that lens is considered one of the best among system devices, being respected for its very good optical properties and a splendid build quality. We decided to check out whether such an opinion is truly deserved and the lens – as good as its users claim.

The lens for testing purposes was lent by the�Fotozakupy.pl shop.

You are also invited to get acquainted with our test procedure, described in the article "How do we test lenses?" If you feel it’s still not enough, please go to our FAQ section where you can find some further explanation.

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Pentax SMC FA 31mm f/1.8 AL Limited - Lab Test / Review - Analysis

Lens Reviews - Pentax

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Distortion

The Pentax SMC FA 31mm f/1.8 Limited exhibits only slight barrel distortion (~0.8%) which shouldn't be really field relevant.

Note: We didn't retest this aspect because it cannot change just by moving to a different body using the same sensor size.

Vignetting

As a full format lens the 31mm f/1.8 enjoys a sweet spot advantage on Pentax APS-C DSLRs. Nonetheless vignetting can be quite obvious at wide-open aperture (1EV). The problem is gone by f/2.8.

MTF (resolution)

The FA 31mm f/1.8 Limited produced excellent resolution figures in the MTF lab. At f/1.8 the center performance is already very good both in the center as well at the borders. The corners are a bit softer here. The quality increases a bit when stopping down to f/2.8 with a center reaching excellent levels followed by very good borders and corners. The quality remains exceptionally high all the way down to f/11.

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 for sharpness. If you want to know more about the MTF50 figures you may check out the corresponding Imatest Explanations