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Monster Adapter LA-KE1: A Report

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Category: Equipment forums
Forum Name: Adapters and converters
Forum Description: Discussions for various adapters and converters
Printed Date: 02 June 2023 at 23:35

Topic: Monster Adapter LA-KE1: A Report
Posted By: butangmucat
Subject: Monster Adapter LA-KE1: A Report
Date Posted: 19 December 2021 at 12:24
This post was originally posted on - , as this is about a Pentax K to Sony E adapter. I feel that the information might also be useful to members here, therefore I am cross posting the exact same content here.


I have been away from the forum for quite a while now. Over the years, I have officially graduated from college with a CompSec Major and a Media Studies Minor and am about to graduate from graduate school with a CompSec major. While I no longer practice photography as a curriculum, it is still a part of my life. I have let go of my trust a7 and moved to the modern a7C, which in turn allowed me to reliably autofocus even with adapted lenses. While I have initially took advantage of this by selling off some of my older lenses (mostly Minolta, but also a few pre-AF Nikon and Pentax) and acquiring some Canon EF lenses, I have always wanted to use my FA43 and FA31 lenses, which have been with me since I first took photography courses in college, with full PASM exposure modes and AF support. Therefore, when I learned that Monster Adapter's - LA-KE1 became available back in China, I ordered mine using my internship compensations, and have it shipped to me.

I have received the adapter for a month now, and while I have been busy with graduation for the past few weeks, I did manage to use the adapter with my three Pentax AF lenses (FA31, FA43, and DA40XS - another recent purchase). As a part of after-sales services for Chinese buyers, I am in a chat group where both representatives from the Chinese distributor and Monster Adapter is available, but I am not otherwise affiliated with either of them.

Build Quality

The lens adapter is well built with anodized aluminum, and both the lens and body mounts are metal. There are two bumps on the barrel that houses the aperture actuator and AF motors. Inside the lens mount, there is a small switch that can force Kaf2 lenses to use either the built-in SDM or screwdrive for AF. There are no USB ports on the adapter, as all firmware updates are done using the camera body, just like genuine Sony lenses and adapters. However, at least on my copy, there is a shiny white metal rail right next to the aperture actuator, which I painted black myself with acrylic paint marker.

Without the paint job, the metal rail can introduce quite some reflections (shot with FA31):

Compatibility and Performance

Just like other Monster Adapter products, this adapter has an "allow list" for lenses and bodies. Lenses and bodies not on the allow list would get no AF functionality. The full list of supported lenses and bodies can be found on the Monster Adapter link in the first chapter. I have been using this adapter with my FA31, FA43, and DA40XS lenses without major issues. Support for in-lens motor (Kaf3) and electromagnetic diaphragm (Kaf4), however, is not present in the current firmware at all.

This adapter emulates a Sony LA-EA3 adapter, just like the "green mode" on Metabones adapters. AF-S mostly works, but with my FA43 or FA31 wide open (especially with the "flex spot" AF mode), sometimes the image can be completely out of focus. AF-C (including Sony's new "real-time tracking" AF) also mostly works (it can catch up with moving trains, at least), but sometimes with my FA43, the adapter can drive the lens all the way to MFD and get stuck there (I mainly use the "tracking expanded flex spot" option), and never finding the target again. Eye AF also works to an extent in AF-S mode (demonstrated with the DA40XS lens):


A major quirk of the adapter is that the aperture actuator is fairly slow to respond compared to my other adapters (LA-EA4, Sigma MC-11, and Metabones Mark IV). As a result, the shutter lag is significantly longer than that of using my other adapters, and the max continuous speed seemed to be capped at around 1fps. Wide open, however, allows achieving the 3fps cap of the LA-EA3 adapter (when used on non-a9 bodies).

When a DA lens, such as the DA40XS is being used, the a7C body would by default switch to APS-C mode. While one can force the body to work in FF mode, the phase detection area of DA lenses (at least in the case of my DA40XS) will be limited to the center of the frame (the same holds true for APS-C mode, but to a much lesser extent):

While the Metabones Mark IV adapter has a similar limitation under "advanced mode," it will allow contract detection outside the PDAF box. This adapter does not allow CDAF at all.

Sony does not support some of the max F stops present in the Pentax lineup. For example, the max aperture of my FA43 is displayed as F2.0.

The lens name in the EXIF data are not the ones given by Pentax. For example, my FA43 becomes "E 43mm F1.9" and my FA31 becomes "E 31mm F1.8" respectively. My DA40XS, however, seems to be recognized by DxO as the Canon EF 40mm F2.8 STM lens (and DxO keeps trying to apply the wrong profile). The latter seems more to be an issue with DxO though, as I have also seen such misidentifications on adapted Minolta glass (using the LA-EA4 adapter).


The LA-KE1 from Monster Adapter is quirky. But if you can work within its limitations and happen to have compatible lenses, it can be very useful. In fact, I bought the DA40XS just for this adapter - so I can easily add it to my EDC kit and use it just like a GR. However, if I need to photograph moving subjects, then the adapters for Canon lenses are still more mature and more suitable.

Sample Images





Posted By: QuietOC
Date Posted: 19 December 2021 at 12:47
Thank you for the review!

I have a 43mm Limited which I don't care much for, but I am interested in the 31mm and the 77mm Limiteds. I sold the XS in favor of the Canon STM. The Canon doesn't get recognized as itself on any of the adapters I have.

Pentax Q7 5-15 15-45/2.8 8.5/1.9 11.5/9

Posted By: butangmucat
Date Posted: 19 December 2021 at 13:03
Originally posted by QuietOC QuietOC wrote:

Thank you for the review!

I have a 43mm Limited which I don't care much for, but I am interested in the 31mm and the 77mm Limiteds. I sold the XS in favor of the Canon STM. The Canon doesn't get recognized as itself on any of the adapters I have.

I have both. Sometimes the thickness difference is all it is needed to put everything together in an EDC kit.

DxO recognizes the Canon STM 40 correctly on either MC-11 or Metabones Mark IV, and applies the lens profiles. That's also why I just can't uninstall the profile for this lens and call it a day.

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