Pentax SMC DA* 300mm F4 ED[IF] SDM – Review 2021

The Pentax SMC DA* 300mm F4 ED[IF] SDM ($1,099.95) is a premium telephoto lens, compatible with APS-C cameras from Pentax. It’s an older model, but one that may still hold some appeal to photographers stepping up to the K-3 Mark III. As part of the premium DA series it’s built to high standards, with weather protection and a metal barrel. It’s not the best performer in the field, though, showing results that aren’t always razor sharp, and sometimes struggling to hit focus.

Sized for Handheld Photography

The DA* 300mm isn’t the longest prime you can get for your Pentax camera, that honor goes to the telescope-sized DA 560mm F5.6 (20.5 by 5.1 inches, 6.7 pounds). The DA 300mm doesn’t offer the same reach, but it’s much better sized for handheld work. It measures 7.2 by 3.3 inches (LW) and weighs about 2.4 pounds, quite reasonable given its angle of view and aperture.

The barrel is metal and includes an integrated tripod foot. It doesn’t include the Arca-Swiss dovetail mount, so you’ll still need to add a quick release plate to use with a tripod. The foot rotates so you can swap between landscape and portrait work without fiddling with the tripod head.

Like most Pentax SLRs, the DA* 300mm includes dust and splash protection, so you can comfortably use the lens outdoors, even in inclement weather. Its front element doesn’t include any sort of anti-smudge fluorine (it wasn’t a common feature when the lens was developed), so you’ll have to rely on the lens hood to protect it from raindrops and stray fingerprints.

Autofocus is internal, driven by an internal focus motor, based on Pentax’s Supersonic Drive Motor (SDM) tech. It’s certainly quiet and the lens supports full-time manual override, without having to switch your camera’s focus mode. There’s also an AF/MF toggle switch on the barrel.

On our K-3 Mark III test body, the DA* 300mm’s autofocus didn’t deliver the same level of speed or accuracy as others with newer DC motors, specifically the HD 150-450mm and HD 20-40mm zooms. It shows some hesitance in locking focus in general and netted enough shots that were just slightly off to raise an eyebrow.

Pentax doesn’t bill the DA* 300mm as a macro, but it focuses quite close for a telephoto. At its minimum 4.6 feet (1.4m), the lens projects objects at 1:4.2 life-size.

Teleconverters are supported. I paired the 300mm with the HD DA 1.4x AW AF teleconverter. It narrows the angle of view to 420mm and the maximum aperture to f/5.6. It’s a definite boon for snapping shots of distant subjects, and I didn’t note any visible drop in clarity with the teleconverter.

Pentax doesn’t put optical stabilization in its lenses, even telephotos. Its SLRs include in-body stabilization instead. The K-3 III does the job of removing the blurry effects of shaky hands from images at shutter speeds as long as 1/15-second with this lens. But you do see every bit of shake through the optical viewfinder. It’s not news if you’re used to Pentax gear, but it’s disorienting when coming over from the lens-based stabilization other SLR systems employ.

In the Lab

I paired the DA 300mm with the 25.7MP K-3 Mark III for testing in the lab and in the field. The optical formula was designed when 15MP SLRs were commonplace, and the DA shows it. It delivers resolution at the bottom of the range we consider good for the K-3 III at f/4 and f/5.6 (2,100 lines). It gets better at f/8 and f/11, netting very good results (2,500 lines).

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There’s no distortion to note, but we do see longitudinal chromatic aberration (LoCa) in images, particularly in defocused backgrounds, and the lateral purple fringing effect in high-contrast areas of the frame. The fringe isn’t too hard to correct in software, but the LoCa is difficult to remove, even with Adobe’s Raw processing tools.

You expect primes to deliver sharper results than zooms, but this is one case where that’s not true. I was able to test it directly against the heftier, $2,000 HD 150-450mm zoom lens and noted that the zoom delivered sharper results wide open at 300mm f/5.6 (2,500 lines) and f/8 (3,000 lines). It falters a bit at 450mm f/5.6 (2,100 lines), but picks up at f/8 (2,600 lines).

In Need of a Refresh

I approached the SMC DA* 300mm F4 ED[IF] SDM in hopes that it’d be a lens I could recommend to Pentaxians stepping up to the K-3 Mark III. The company’s latest SLR has its best-yet autofocus, one that promises to make the system more capable for photographing action, wildlife, and the like.

Despite premium positioning, the DA* 300mm F4 is a bit of a letdown. It doesn’t focus with the speed or acumen of other Pentax lenses, and it doesn’t deliver the quality you expect from a star-line prime with the company’s top-tier camera.

What else is out there? The HD 150-450mm is a better performer on the K-3 Mark III, but it costs $2,000 and is quite hefty. We’ve not yet tested the $450, weather-sealed HD DA 55-300mm F4.5-6.3 ED PLM WR, but it promises to focus more quickly with its PLM motor.

You can also scrounge the used market for venerated zooms like the Sigma 150-500mm F5-6.3 AF APO DG HSM, or add a teleconverter to the premium, full-frame Pentax HD 70-200mm F2.8. But we’d love to see Pentax renew the DA* 300mm, as the older design doesn’t quite match up to the promise of the K-3 Mark III.

Thanks to LensrentalsLensrentals for providing equipment to support this review.