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01-16-2013, 09:16 AM   #1
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pentax 50mm f1.2 vs. limited lenses

Hi,
trying to conquer LBA (or not!) and wanted some opinions. Is the pentax 50mm 1.2 as good as it's prices on fleabay would indicate?
I've picked up a DA40mm ltd and DA70mm ltd which I am loving (both together costing less used then it appears a 50mm 1.2 sells for on fleabay). Wondering if a 50mm 1.2 would add anything to my repertoire that I can't do already.
I can see 2 possible uses - taking shots in low light at events w/o flash (we host events at our business and like to capture the moment for our web-page); second possible use would be for our product shots. Would the 50mm provide more pleasing product shots in a photobox? in terms of DOF and bokeh?
Or do I save my $$$ and buy a lens that does something I can't already do.
btw... I already have a Pentax-A 50mm 1.7 (and a 50mm 2.0).
any thoughts?

Mark

01-16-2013, 10:05 AM   #2
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A couple of thoughts for you.

1.2 is a half stop faster than 1.4, however because each stop is double the previous stop, it has the same amount of additional light capture as the difference between 1.4 and 2. What I'm saying is, it's more substantial than you think.

The 1.2 at 1.2 is actually quite sharp, if nearly impossible to focus on what you want. It is not as sharp wide open as the limited lenses that I own. Remember that DoF on 1.2 at close distances is very very small.

I view the 1.2 as more art glass, or extremely low light. If I need AF, or sharp pictures, I'm far more likely to take my 31/1.8, or possibly the 55/1.4.

The bokeh is amazing though.

https://www.pentaxforums.com/forums/photo-critique/115563-abstract-million-bu...lake-city.html


This one is taken in almost no light:
- Clinton's Album: Best of 2010 - PentaxForums.com


For only the specific use case you're describing, I *think* you would get more mileage from these lenses first: FA* 85/1.4, FA 31/1.8 ltd.

However, don't let this get in the way of your LBA. You can do amazing things with the 1.2.
01-16-2013, 10:30 AM - 1 Like   #3
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I own several 50 and 55 mm lenses and I'm not looking to add to that collection. A 50/1.2 however is lens I would buy if I came across one at a reasonable price. Prices for one are very high and I'm not actively seeking one out but it's one of those legendary Pentax lenses that is certainly worth owning. There are other benefits to a fast lens besides the narrow DOF and bokeh. Back in it's day, cameras were manual focus and fast glass meant very bright viewfinders and a much more accurate focus. All your shots would look better.
01-16-2013, 10:32 AM   #4
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If you shoot film or if Pentax ever releases a FF DSLR then the 50/1.2 is a “normal” lens.
Then the 50mm FL could be one of your most used lenses and you get the bonus of a super fast f1.2.

If Pentax releases a FF DSLR the price of the 50/1.2 will increase dramatically. So if you can get one now I’d go for it.

Phil.


Last edited by gofour3; 01-16-2013 at 05:26 PM.
01-16-2013, 11:47 AM   #5
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QuoteOriginally posted by Clinton Quote
1.2 is a half stop faster than 1.4, however because each stop is double the previous stop, it has the same amount of additional light capture as the difference between 1.4 and 2. What I'm saying is, it's more substantial than you think.
Half a stop is half a stop, wherever it's at.

For the same shutter speed,
ISO 320 at f/1.2 or ISO 400 at f/1.4.

Addressing OP's question,
the low light advantage over an f/1.4 lens is marginal.
01-16-2013, 11:55 AM   #6
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The A50 1.2 was always an expensive lens. In 1991 it retailed for $243.95 or slightly less than it sells for now adjusted for inflation. Don't be fooled by those eBay listings for $700. Most of the completed listings are around $550. A castrated 1.2 just sold for $346.

QuoteOriginally posted by lytrytyr Quote
Half a stop is half a stop, wherever it's at.

For the same shutter speed,
ISO 320 at f/1.2 or ISO 400 at f/1.4.

Addressing OP's question,
the low light advantage over an f/1.4 lens is marginal.
But it has a 9 bladed bokeh vs an 8 bladed bokeh...the 1.7 has a 6 bladed bokeh.

Last edited by boriscleto; 01-16-2013 at 12:02 PM.
01-16-2013, 01:03 PM   #7
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QuoteOriginally posted by lytrytyr Quote
Half a stop is half a stop, wherever it's at.
QuoteOriginally posted by Wikipedia:
In photography, stops are also a unit used to quantify ratios of light or exposure, with each added stop meaning a factor of two, and each subtracted stop meaning a factor of one-half.
Therefore, a stop is either half the light or 2x the light, wherever it is at.

If you start say at 100 light units at f4, you get 50 light units at 5.6, and 25 light units at f8.

Edit: Math fixed. Thx @lytrytyr

If you start with 100 light units at f4, you get 200 light units at f2.8, 400 at f2, 800 at f1.4, and 1600 at F1. The difference between 1.4 and 1 would be 800, but since it's half a full stop we're talking about, it's similarly 400 light units.

Last edited by Clinton; 01-16-2013 at 08:25 PM.
01-16-2013, 02:22 PM   #8
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QuoteOriginally posted by Clinton Quote
If you start with 100 light units at f4, you get 200 light units at f2.8, 400 at f2, and 800 at f1.4. The difference between 1.4 and 1 would be 1600, but since it's half a full stop we're talking about, it's similarly 800 light units.
The difference between f/1.4 (800) and f/1 (1600)
would be 800, so 400 to f/1.2.

If you started with those same 100 light units at f/16,
the difference between f/1.4 and f/1.2
would be 6400 light units by the same kind of reckoning!

However much fun this all is, it makes no practical sense.
In practice, f/1.2 versus f/1.4
is just one notch on the EV compensation scale.

01-16-2013, 03:00 PM   #9
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Pentax does not make the 1.2 anymore so once you have one, someone else does not and you are ahead of the game.
If you can see a difference with your eye, then it is meaningful and you can with the 1.2 vs any 1.4. If you need a machine to detect the difference then it is marginal and meaningless to people. It its like loudness; humans cannot detect an increase/decrease in sound amplitude of 2dB but can if it is 3db.
01-16-2013, 03:05 PM   #10
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QuoteOriginally posted by JVi Quote
Pentax does not make the 1.2 anymore so once you have one, someone else does not and you are ahead of the game.
If you can see a difference with your eye, then it is meaningful and you can with the 1.2 vs any 1.4. If you need a machine to detect the difference then it is marginal and meaningless to people. It its like loudness; humans cannot detect an increase/decrease in sound amplitude of 2dB but can if it is 3db.
Actually, there was a batch of Assembled in Vietnam 1.2s, they just weren't sold in the US. Who knows what Ricoh will do.
01-16-2013, 03:10 PM   #11
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QuoteOriginally posted by boriscleto Quote
Actually, there was a batch of Assembled in Vietnam 1.2s, they just weren't sold in the US. Who knows what Ricoh will do.
Oooooooh!
01-16-2013, 03:30 PM   #12
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QuoteOriginally posted by JVi Quote
Pentax does not make the 1.2 anymore so once you have one, someone else does not and you are ahead of the game.
If you can see a difference with your eye, then it is meaningful and you can with the 1.2 vs any 1.4. If you need a machine to detect the difference then it is marginal and meaningless to people. It its like loudness; humans cannot detect an increase/decrease in sound amplitude of 2dB but can if it is 3db.
"Pentax does not make the 1.2 anymore so once you have one, someone else does not and you are ahead of the game."

I like that analogy and won't sell my pristine copy. I haven't gotten around to using it yet, but carry it in my bag.
01-16-2013, 03:45 PM   #13
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An interesting bunch of replies... kind of confirms my suspicions... If I can find one at a decent price I'd pick one up... after all if I try it and don't find it provides what I need I can always resell it....
01-16-2013, 08:27 PM   #14
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QuoteOriginally posted by lytrytyr Quote
The difference between f/1.4 (800) and f/1 (1600)
would be 800, so 400 to f/1.2.
Ah you are correct sir. My math was incorrect. I fixed it above.

QuoteOriginally posted by lytrytyr Quote
However much fun this all is, it makes no practical sense.
In practice, f/1.2 versus f/1.4
is just one notch on the EV compensation scale.
I have both, and I can say from shooting experience, it lets me shoot things in the near-dark that F1.4 doesn't. I guess I'm saying it's more than you expect.
01-16-2013, 08:54 PM   #15
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The SMCP-K 50mm f/1.2 is a brilliant lens however, to really get the most out of this lens you need to have a K5IIs - at f/1.2 the Bayer AA filter really gets in the way with ultrafast lenses because they don't have much contrast at wide apertures, and the light scattering properties of the bayer AA filter really hampers the IQ at f/1.2

From what my testing has shown that the SMCP-K 50mm f/1.2 is an excellent performer when stopped down - many ultra-fast primes typically do not perform much better than the average 50mm, but the pentax lens seems to improve upon that - so owning one isn't just about bragging rights as there are considerable gains in image quality.


Pentax K5IIs - Pentax SMC-K 50mm f/1.2 @ f/5.6 ISO 100 - inset 100% crop, basic sharpening in LR4


Pentax K5IIs - Pentax SMC -K 50mm f/1.2 @ f/1.2 1/1600th ISO 80 - Sharpened in LR4, slight tonal adjustments (light fall off on the 50mm f/1.2 isn't really that bad)

Last edited by Digitalis; 01-16-2013 at 10:59 PM.
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