[br.davidson]

Like every other Pentax user, I've spent plenty of time coveting the legendary 31mm f/1.8 Limited. I even rented it for a week and loved the results I got from it. Whenever I get close to actually buying it, however, I realize I already own the fast wide/normal lens that I really want anyway. I'm talking about the 20mm f/1.7 m4/3 lens. Bear with me. Both have similar effective focal lengths (46mm vs 40mm).

Why do I like the FA31? It's compact, fast, useful focal length on APS-C, great build quality, fantastic image quality from wide open

The Panasonic 20mm f/1.7? More compact, tiny bit faster, almost perfect from wide open, great price

All I give up with the Panasonic is build quality and somewhat more DOF. Wide open, the 20mm easily gives the FA31 a run for its money. And it's a lot of money at that. The Panasonic only costs 1/3 of what the FA31 costs.

For more perspective, consider this:
w/o viewfinder:
K01 + FA31 = $1,750.00
GX1 + 20mm = $1,049.00 (with far cheaper camera choices)

w/ viewfinder:
K-r + FA31 = $1,500.00
G3 + 20mm = $950.00

The FA31 feels better than any other lens I've ever used and its image quality is truly something special, but for everyday use I'm thinking a m4/3 camera with the 20mm is a better option. Look past the pixie dust and try to convince me otherwise.

[JinDesu]

A smaller sensor system will allow for short fast lenses at a much cheaper rate - you are comparing a M4/3 lens with a Full Frame lens, and one of older origins (price-wise).

Your argument can easily apply against any of the classic legends from Zeiss and Leica - there are reasons why those lenses command a high premium.

[eddie1960]

2 things you ignore. the apsc options will have significantly better high iso performance. the second is DOF possibility. a 31 1.8 is more like a 20 1.2 in m4/3 from this characteristic.
there is also in apsc the option of the Sigma 30 1.4 which by all accounts is a very standout lens at a much lower price

[br.davidson]

@JinDesu: You're right about the huge difference in age and sensor size between the two lenses, but I'm not seeing a full-frame Pentax or a FA31 replacement anywhere in the near future. Where's my DA27 f/1.8 Limited, Pentax? I'm looking at this comparison more to examine my personal changing perspective rather than the two lenses as absolutes. Others may place build quality and image "drawing" abilities higher on their priority list with price towards the bottom.

@eddie1960: Not sure about significantly higher ISO performance from best APS-C vs best m4/3, but the advantage will always go to the bigger sensor. As for DOF, the FA31 @f/1.8 on the K-7 has a DOF of 2.27 ft at a focus distance of 10 ft while the 20mm @f/1.7 has a DOF of 3.96 ft. For equivalent DOF, move closer to your subject by 2.3 ft with the 20mm. The Sigma's an interesting option, but I value edge to edge sharpness too much for that.

This comparison probably makes no sense to number crunchers and it is clearly a bit absurd, but thinking about weird comparisons like this one can help illuminate your personal preferences better than the usual FA31 vs DA35 vs Sigma 30mm comparisons. I already own the 20mm and I've been surprised at just how few lenses can beat it by a large enough margin to justify a purchase.

[disya2]

When rational arguments can't help it's time to consider mystique ones I had 77mm for somewhat long time and I was hooked by its magic from the very first shots. However, when I get FA 31mm, I couldn't understand why it doesn't do what 77mm does. Yes, it produced very sharp images stopped down to 2.8 (it is not exemplary sharp at 1.8) but I couldn't feel anything magically in them. Things changed after few hundred shots. I gave up trying to make a blurred background (yes, silly me) and didn't hesitate to set f4-f5.6. And that was the time I finally got it. 31mm has their magic indeed. It is different and harder to reproduce but very powerful. Tiny details combined with great micro contrast (I'm not sure I use the right term here) yield images which are enjoyable to my eyes and I want to look at them again and again. It also shows itself on wider apertures but not that often.. or maybe I don't know how to cast it . That is 31mm's magic. I don't know if Panasonic lens has it.

[br.davidson]

@disya2: It sounds like it took a few hundred shots for the pixie dust to kick in The "magic" difference between certain lenses usually shows up in the bokeh, but you're right that it can show up in pictures with more DOF too. I've got the DA15 and DA35 and neither one has great bokeh (let's call it "interesting" to be polite), but their rendering is unmatched as far as I'm concerned. What I found when I first tested the Panasonic 20mm was that it was sharp across the frame right from f/1.7. I'd used mostly older fast lenses like the FA31 and FA50/1.4 prior to that, so I expected the usual soft haziness wide open. As you say, it takes a while to figure out if the magic is there in terms of rendering and it's still too soon to tell.

One thing I forgot to mention: focus speed for the 31mm on the K-7 was way faster than the 20mm on a GF2. Not surprising, but should be mentioned.

[RioRico]

I'll veer slightly, since I've had none of the above, but consider this parallel: Last year I got a K50/1.2 for US$250 and a Sears-Tomioka 55/1.4 for US$2.25 shipped. These have nearly identical DOF. Is the 50 really worth 111x the 55?

I have a fine Vivitar-Komine 28/2 CFWA that cost me US$18 shipped. The 31Ltd costs around US$1k. Is the 31 really worth 55x the 28? For comparison, my AFs cost an average of US$300 each, my MFs averaged US$15, a 20x difference.

The answer, of course, is that we pay 95% more for a 5% performance increment, something like that. But I'll need to knock-off a few more relatives or minimarts before I can afford a US$1k lens. That's 'afford', not 'justify'. No hope...

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Last edited by RioRico; 03-19-2012 at 01:40 PM.

[Ubuntu_user]

Just wait, when Pentax releases a FF, then the FA 31mm will astonish everyone. It's fantastic on APSC, but on FF? ...There's nothing like it.

[br.davidson]

AF seems to demand a hefty premium, but maybe that won't be the case 30 years from now, who knows? I like your examples. They show just how far the cost game can go. What you really have to ask yourself is if a coffee from starbucks is worth 2x what you paid for your 55/1.4 lens. Things always get a little murky when cost is part of the equation. How is that Vivitar 28/2 by the way? Is it easy to find one for $18?

[JoostW]

Carl zeiss distagon 35mm f/2 ... already more nice than the highly (over)rated Fa 31mm ltd. And i hope to use it on a FF anytime soon .

[vrrattko]

That's unfair - comparing Pentax lenses to Carl Zeiss.
Just kidding...Carl Zeiss lenses are superb, some Pentax glass is excellent also....

[RioRico]

AF seems to demand a hefty premium, but maybe that won't be the case 30 years from now, who knows?

Samyang makes some nice MF lenses right now at good low prices, and the Horusbenno (?) 50 gets pretty good reviews, so MF still seems cheaper than AF. But in a few decades, ?quien sabe? Who know, indeed?

I like your examples. They show just how far the cost game can go. What you really have to ask yourself is if a coffee from starbucks is worth 2x what you paid for your 55/1.4 lens.

I don't do Star*ucks and I'm not allowed anything stronger than decaf (I start my day with Depresso, decaf espresso) but even an oganic eggplant wrap from Trader Joe's isn't worth 2x that Tomioka 55. BTW this leads to one of my lens-buying rules: If it costs less than a sandwich or burger, grab it! That's a great weight-control program too.

How is that Vivitar 28/2 by the way? Is it easy to find one for $18?

I got lucky one week last year. First a Vivitar-Kiron 28/2.5 for US$20; then a Tamron BBAR 28/2.5 for US$4 including Adaptal2-PKM adapter; and finally the Vivitar-Komine 28/2 CFWA for US$18. A trifecta! And all in straight-up auctions, with no misspellings, no blurry product shots, no mysterious batch-lots.

Both Vivs were in Nikon mount, which takes about 3 minutes of Dremel work to mod to PK. I don't know if they're hard to find 'cause I haven't had to look since then. I hear that the 28/2 CFWA goes for more in M42 or PK mount. But Nikon, Olympus OM, and Yashica C/Y lenses are easy to mod for PK, and OM and C/Y Vivitars don't demand high prices.

How is the 28/2 CFWA? It's my most-used prime. Besides my basic zooms kit and my ultralight minikit, I'm likely to carry the 28/2 CFWA and a modded Nikkor 85/2 most of the time. They're just indispensable for me.

[rparmar]

A long time ago I started the thread Vivitar 28mm As FA31mm Replacement? which eventually spawned the Vivitar Bestiary. The upshot is that Vivitar produced some very nice manual focus lenses that are now a perfect normal for Pentax DSLR. The Close Focus varieties are pretty well guaranteed to take photos as nice as the person behind the camera will permit.

I own the Panasonic 20mm and don't use it much, since it's not my focal length. Good though it is, I'd gladly trade it and my Vivi Close Focus for the FA31 Limited. So, if anyone is up for that offer... ;-)

[rparmar]

Carl zeiss distagon 35mm f/2 ... already more nice than the highly (over)rated Fa 31mm ltd. And i hope to use it on a FF anytime soon .

No-one is going to argue against Zeiss, but what does this mean exactly? In what way is the FA 31 Limited over-rated?

[twitch]

Yikes the FA31 is not over rated, it has a big reputation here but it deserves every bit of it and more. It's hands down the best lens I've ever had the pleasure to use, the best amongst this not-so-shabby group anyway.

Just wait, when Pentax releases a FF, then the FA 31mm will astonish everyone. It's fantastic on APSC, but on FF? ...There's nothing like it.

Indeed, on film it is fantastic and I can't imagine it losing any magic on FF digital.