31 mm ltd

I too have always had a feeling Pentax deliberately chose those very unusual focal lengths to stand out from the crowd. Adds a little mystic and kudos to the brand.

/Ian

You may have a point there mph.

However the 43mm is as close as you can get for 35mm or FullFrame these days.

The 31mm is in reality too long to be a true "naked eye" lens on a cropped sensor, the closest to true is the 28mm,(science bit - the hypotenuse is just over 28mm on APS-C and just under 43mm on FF) but Pentax have never had a fast 28mm, so the 31mm is the closest we can get.

The 77mm is more of an unusual length, but small enough to be a nice small lens that can be fast and did'nt step on the FA*85mm F1.4's shoes.

Even now the three FA Limiteds are still revered alongside the Leicas....

All I can say is that thank god that Pentax have thought outside the box and not gone with the flow with lenses and made 3 of the finest small fast lenses you can buy (or should I say a further 5 with the 15, 21, 35M, 40 and 70 Limiteds too)
Wish I could afford them all....

The FA43 has the focal length it does because 43mm (rather than 50mm) was the true 'normal' lens (focal length = diagonal of format) on 35mm format.

Some of it is definitely marketing-- the FA77 was named because "7" is a lucky number. Really the focal length is a bit longer. But it is a lucky lens.

I wouldn't say it's too long. It's still shorter than 50mm is on FF.
And as for fast 28s, there were K28/2, and M/A28/2. Fast enough IMO, considering they are wide angle FF designs from few decades ago... The only reason why they don't make one now IMO, is that it would more likely kill off 31ltd if it was comparable price and DA* (meaning WR + SDM - or DC)

my 2p

"are more like 25mm. Only Zeiss admit this I think"

Actually John, they do not. I assume you refer to the Contax/Zeiss 25mm f2.8 Distagon which Zeiss have made since the 1960's and now make for Nikon/Canon etc.

I will let you into a secret....this very old Zeiss design is actually a 26mm lens! The actual focal length is approx 25.8mm....so Zeiss have actually been a bit naughty calling it a 25mm lens.

cheers Steve.

And so the plot thickens! So the 25mm is nearly a 26mm, which in one way is almost a 28mm....goodness, who can we trust?

...and can they be sued.

If you can show lost earnings then you could sue. I can see the case now: "Your honour, my client bought this lens in good faith as a 25mm focal length but has since discovered, to his intense dismay, that it is in fact a 25.8mm..."

well it could throw out all your calculations for the FOV you wanted.

Going back to the original post, I thought I read something somewhere that stated the FA 31 was closer to 32mm.

Was it also not the case that the M and A seriues 28's were closer to 30mm than 28mm

Regards - Steve

My notes show that it tested on the bench to 31.81mm f/1.82, but I do not have a reference.