Monster Adapter LA-KE1 Pentax K to Sony E Lens Adapter

Conclusion

The LA-KE1 K-mount to E-mount adapter fills a niche in the photography ecosystem. It has no true equivalent, as it is the only product allowing the use of Pentax lenses on Sony mirrorless cameras while retaining autofocus, auto exposure, and EXIF recording.

The adapter, created by a small Chinese company named Monster Adapter, is part of a lineup also including adapters to mount Nikon, Minolta and Contax N lenses to Sony. Despite not being part of the usual suspects when it comes to photo equipment, Monster Adapter has developed a solid product, with ongoing support and product development over the last few years.

Physically, the adapter is impressive. Sleek, rather elegant, with a metal body and a solid feel. The AF/MF switch is well placed and easy to operate. It would have been nice to make the adapter weather resistant, to match the large number of Pentax lenses and Sony bodies which are WR. Regardless, the adapter inspires confidence.

The adapter is easy to mount and use. This is probably its biggest strength: with any supported lens, it operates as a native lens would. This means the camera will focus, control exposure, track moving subjects, record the proper information into the EXIF file. Operation is automatic, as it should. Users familiar with perfectly silent Sony lenses with blazing fast AF might be surprised to suddenly hear their camera make noises when operating a screw-drive lens; the adapter does not change how a lens operates, but simply bridges the communication between camera and lens.

Autofocus performances are, in a word, excellent. In most of our test cases, focusing on a Sony camera was faster than using live view on a Pentax DSLR, if slower than using the viewfinder. Results vary with each lens and each AF motor type, but in general the adapter is close enough to what one gets on a Pentax body as to make no difference. Pentax lenses tend to be slower to focus than E-mount equivalents but the adapter does not make them slower. Lenses which are more reactive on Pentax bodies (such as the D FA 28-105mm we tested) feel perfectly adapted to Sony cameras.

The large (and increasing) number of lenses supported by the Monster Adapter is reassuring. There is clearly a bias towards primes, but with 64 lenses currently supported and new ones being added regularly, the LA-KE1 goes beyond the basics.

The biggest question is: who should use this adapter?

The first class of users who will benefit from it are Sony users interested in the unique rendering of some Pentax lenses such as the Limited lenses. Even with the adapter, a FA 43mm or FA 77mm is smaller than a native equivalent on the E-mount, in addition to having a rather unique character. It is possible to use the FA Limited (not the DA Limited) with a dumb, manual adapter, but the benefits of autofocus, auto exposure and accurate EXIF is hard to understate. Other, less exotic lenses can also make a lot of sense. For instance, the D FA 28-105mm plus adapter is the same size as the Tamron 28-75mm F2.8, a lens with a faster aperture but a shorter range. There is no true equivalent for the 28-105mm on the E-mount. Similarly, many compact Pentax DA primes have no direct equivalent, or those equivalents are bulkier and heavier.

A second group is made of current Pentax users who are interested in transitioning to Sony. For those, the LA-KE1 can be a way to ease the transfer by re-using current lenses. 

A third group, perhaps the most numerous, is made of photographers maintaining both systems. For these, the LA-KE1 can be an extremely useful tool in their kit, making it easier to get the best of both worlds.

A last group is those stuck with an early-days SDM lens with a faulty AF engine. The adapter offers a unique extra feature, the ability to deactivate the SDM motor and rely on screw-drive. For some, this could let them revive their defective lenses (at the cost of a Sony camera body, of course).

Our comments are based on firmware v03, and anyone having formed an opinion with a previous firmware update should take that into account. The LA-KE1 is getting more mature, but it is still an evolving product. In its present state, it delivers performance good enough to warrant our consideration.

Pros

• Very good build quality: solid and durable
• Useful AF/MF switch often lacking on Sony bodies
• Reliable metering and EXIF data recording
• Works in AF-S and AF-C
• AF is in general comparable to results with Pentax bodies
• G Driver 2 does improve AF with screw-drive lenses
• SDM/screw-drive switch can force screw-drive on dual systems lenses
• 64 lenses supported at time of writing
• Constant firmware support from manufacturer

Cons

• No weather resistance
• Some features are dependant on the camera body
• Some reported instabilities in rare cases
• Lenses must be specifically included in firmware

Pricing

The Monster Adapter LA-KE1 commands a street price of $439 in January 2023.

The Bottom Line

It's always good to have options. The LA-KE1 is just that: an extra option in the photographer's toolkit. It isn't for everyone, and it's not perfect, but it IS very good at what it does, and completely unique on the market. Its price is less than that of most lenses. For these reasons alone, we are happy that it exists.