I am revisiting the Pentax 645 FA 150 mm ƒ2.8 (IF) lens

Originally created for the analog Pentax 645 system, which however later also had an 51 MP digital equivalent, albeit with a smaller format (33x44). Which means the same sized sensor that Pentax 645, Fujifilm GFX and Hasselblad uses today. Therefore, you have a crop factor on all of your lenses.

In the case of the Pentax 645 FA 150/2.8 [IF] lens, it becomes equivalent that of a 120 mm telephoto lens. A longer portrait lens so to speak. Since I do not have this particular AF lens - but it's manual sibling, called Pentax 645 A 150/3.5 lens, as well the larger brother from the Pentax 6x7 camera system, the Pentax 150/2.8 lens - i can at least access the feeling from such a focal length on portraits.

I made a few images with the Pentax 6x7 Takumar 150/2.8 lens on Sal and myself in the photo studio - already, 1.5 years old.

Pentax 645 FA 150 mm ƒ2.8

In the studio it showed to be a VERY nice focal length for portraits - and the sharpness was top notch once you stop down just a little bit. Kind of like all classic mediumformat lenses. Especially the Pentax 6x7.

With such lenses, whether 645 or 6x7, you don't deal with any / barely any vignetting simply because the image circle are a lot larger then that of a Fujifilm GFX sensor with 33x44 mm

Specifications

The SMC Pentax 645 FA 150/2.8 [IF] - is a surprisingly small and light lens: 500 gram without lenshood. It support Autofocus on the Fujifilm GFX via the Fringer P645-GFX adapter. That is also the reason why I find it suddenly to be more interesting to use as a "on-the-fly" portrait lens. Especially given the smaller and in particularly the lighter weight !

The optical formula is made out of 7 elements in 7 groups. From the era of analog film great - but of course, a modern digital version would most likely have several more optical lenses. With film lenses you often get some fringing on a digital sensor camera, when used wide open.

The min focus distance is 120 cm equivalent to a magnification of 0.15x - so pretty ordinary. (albeit they might refer to the original 6x4.5 format, while a 33x44mm sensor is smaller, and therefore a motive appears larger when focused at min. focus distance) The Min focus distance is actually a snap closer compared to the older , manual Pentax 150/3.5 lens (which is 140 cm).

It is an internal focus lens - meaning, that it doesn't get shorter or longer while focusing. Its filter diameter is 67 mm Ø

If I would import such a lens, second hand - i would have to pay in full around 6500-7000 SEK / 645 € with all important and Swedish tax included. Still clearly cheaper than a new Fujinon lens. Which by the way does not exist in this focal length.

What people write in the Pentax forum ?

One reader writes that it is a very sharp lens - possibly slightly softer compared to a Sigma ART 135/1.8 on a digital body. The latter by the way, is highly regarded and plays among the top 135mm lenses. Which also appears to work very well on a Fujifilm GFX body (with the Fringer EF-GFX adapter).

Now I am not interested into 135mm lens, simply because it is too close to my Fujinon 110/2 lens. Plus I also have the Canon EF 135/2 L - which works without much vignetting, but only at portrait distance. While at when focused at infinity, it vignettes visibly.

Another reader wrote; it is too soft at wide open aperture ƒ2.8 for his liking - but becomes very sharp 1 stop closed down to ƒ4. It combines a beautiful bokeh in the range between ƒ2.8 and ƒ5.6 (which his images confirm - looking lovely).

Overall, you can't go wrong with this lens whether you use it on analog Pentax 645 cameras, digital 645 ones, or perhaps even on a Fujifilm GFX camera with help of an adapter. Then again; the Finger P645-GFX also supports AF, EXIF and IS now - which makes the lenses even more attractive. Plus the lesser weight compared to other lenses often approaching 1 kilo.

What in there for me ?

Good question. Like so many theoretical desktop ideas - it says not much how a lens actually is in reality - and how I would feel about to work with it.

To begin with, I will definitely first use my manual Pentax 645 A 150mm ƒ3.5 lens - and see where that one is going when mounted to the Fujifilm GFX camera, with help of the new Fringer AF adapter. (still providing EXIF and IS).

That lens is ridiculous small and even lighter with 435 gram and creates gorgeous bokeh. I suspect however that it exhibits more fringing or better said; ["longitudinal CA's / CA = Chromatic aberrations ], since it only exhibits 4 optical elements in 4 groups.

It might be enough for me as a portrait lens "on-the-go" - given that I may not use it that much overall. Then it would really enough with the manual version.

Readers report, that despite just 4 optical elements in the manual 150mm version, it too performs impressively (even when they used it on their digital Pentax 645D / Pentax 645Z cameras). Well, that sounds lovely. And as i expected, reports of "longitudinal CA's " are reported between ƒ3.5 and ƒ5.6

Ergo

So, before throwing out 7000 SEK / 645 € on an Autofocus version of the 645 Pentax 150mm lens, I rather test Keeping in mind, that there is no urgency for me to acquire a 150mm lens for portraits (for the Fujifilm GFX camera system). Especially not in the studio, since I can adapt so many other lenses in that focal range.

Then - using the native Fujinon GF 110/2 lens - is a class of its own.

So, there is that.

Well, we men love mechanical, electronic and digital things, don't we ? It is always a bit exciting to acquire and use a "new" lens, testing how older lenses perform on newer digital bodies. While I am not any longer keen on doing that with fullframe cameras - but mediumformat lenses on mediumformat bodies - is always exciting to test. Especially now that the Pentax 645 FA lenses can do autofocus on Fujifilm GFX cameras.

Such developments haven't happen every day.