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01-28-2011, 06:25 PM   #76
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QuoteOriginally posted by Clinton Quote
In terms of photons reaching the sensor, I believe it's the same difference as between 1.4 and 2.8.

Lets say you have 100 photons reaching the sensor at F1, you then have 50 at F1.4 and 25 at F2.8
Half the difference between F1 and F1.4 would be 25, so I believe at F1.2 you'd have 75 photons reaching the sensor, or a difference of 25 photons from F1.2 to F1.4 and a difference of 25 photons from F1.4 to F2.8. It's only a half stop, but it's a half stop at the top of the spectrum. It may mean more light than you'd think otherwise.
Why wouldn't it be 100 photons at f/1, 75 at f/1.2, 50 at f/1.4, 25 at f/2 and 12.5 at f/2.8?

01-28-2011, 06:38 PM   #77
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QuoteOriginally posted by dgaies Quote
Why wouldn't it be 100 photons at f/1, 75 at f/1.2, 50 at f/1.4, 25 at f/2 and 12.5 at f/2.8?
Each full stop halves the amount of light; however I believe half stop measurements are measured as halves between the next full stops. If I'm incorrect, and all stops are on a curve, it's still 100 at F1, 50 at F1.4, and 25 at F2.8. F1.2 would just be somewhere along the curve between 100 and 50.
01-28-2011, 06:50 PM   #78
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the scientific discussion makes me think of starwars and star trek. firing photon cannons, arm photon torpedoes, raise shield and long live and prosper.
01-28-2011, 06:50 PM   #79
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QuoteOriginally posted by Clinton Quote
Each full stop halves the amount of light; however I believe half stop measurements are measured as halves between the next full stops. If I'm incorrect, and all stops are on a curve, it's still 100 at F1, 50 at F1.4, and 25 at F2.8. F1.2 would just be somewhere along the curve between 100 and 50.
Yeah, but aren't f/1.4 and f/2.8 two stops different, with f/2 in between. So f/2.8 would have one-quarter the amount of light as f/1.4.

01-28-2011, 07:14 PM   #80
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1.2 --> 1.4 = half a stop; 1.4 --> 2.8 = 2 stops; so your math was just a little off, Clinton, I think you missed the f/2 stop.

That wouldn't be a bad math-rock song title, "I missed the f/2 stop". Well, maybe it would be, I don't know.

Also, I think it makes more sense to say that the K 50/1.2 isn't sharp enough for a given person's uses, rather than to say it isn't sharp. Because I find the A version sharp enough in the plane of focus, when I can find the plane of focus, and when I "need" f/1.2.
01-28-2011, 07:29 PM   #81
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QuoteOriginally posted by Nick Siebers Quote

Also, I think it makes more sense to say that the K 50/1.2 isn't sharp enough for a given person's uses, rather than to say it isn't sharp. Because I find the A version sharp enough in the plane of focus, when I can find the plane of focus, and when I "need" f/1.2.
you said it best Nick. it is rather incorrect to say that the K/A 50/1.2 isn't sharp. as far as I had seen it, it is sharp at the wider openings. the recent tests conducted by dgaeis and Peter showed the capability of the 50/1.2 not only an ultra-fast lens, but a very capable general purpose sharp lens at all apertures.
01-29-2011, 06:21 AM   #82
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QuoteOriginally posted by Clinton Quote
In terms of photons reaching the sensor, I believe it's the same difference as between 1.4 and 2.8.
No, not at all. Between 2.8 and 1.4 there are two stops. Between 1.4 and 1.2 it's not even half a stop (just 0.44).

QuoteOriginally posted by Clinton Quote
Half the difference between F1 and F1.4 would be 25, so I believe at F1.2 you'd have 75 photons reaching the sensor, ...
It would be 69.44 photons.

QuoteOriginally posted by Clinton Quote
... or a difference of 25 photons from F1.2 to F1.4 and a difference of 25 photons from F1.4 to F2.8.
Between 1.4 and 2.8 it's a difference of 38.26 photons and between 1.4 and 1.2 it's a difference of 18.42 photons.

QuoteOriginally posted by Nick Siebers Quote
Also, I think it makes more sense to say that the K 50/1.2 isn't sharp enough for a given person's uses, rather than to say it isn't sharp.
Well, you of course have a point but such relative terms are not very useful. Someone may find that single element close up filters produce sharp images with acceptable CA. Fine for that person, but that shouldn't stop the majority to deem single element close up filters to yield only mediocre quality (which is why, e.g., the Raynox is a two element filter).
01-29-2011, 06:44 AM   #83
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From the other point of view, just because some find one element close up lenses produce only medicore results, it doesn't mean the rest of must think alike..

There's no winning in here... Personal opinions and mileage may vary....

01-29-2011, 02:39 PM   #84
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Silly me, here I am missing a full stop. I think the photo cop may tag me with a failure to obey a semaphore.

Nobody knows the stops I've missed. Nobody knows my photons. Nobody knows the stops I've missed. Glory Photollelujah.
01-30-2011, 10:33 AM   #85
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QuoteOriginally posted by Rondec Quote
capture a moving target at f1.2 have my kudos, but it is way above my skill level.
This is an interesting observation, because 90% of the images I've seen posted of the 50mm f1.2 are of stationary or near-stationary objects.

The DOF and sharpness at f1.2 are so unforgiving that I would likely never use the lens lower than f2. If I was going to spend that kind of coin, however, I think I would prefer the results from the FA 43 over the 50 1.2 (not to mention how much easier it would be to manually focus an f1.9 lens over an f1.2 on a DSLR). I really don't think anyone would use a lens like the 50mm 1.2 for low light over an f2 lens, because the hit in image quality is often less just bumping the ISO a stop and post-processing (instead of working with almost no DOF at all). This was the experience I had with the 50mm 1.4 vs. the 1.8, and even the 2.8. The light gathering ability did not offset the hit in IQ due to an unforgiving DOF (hence why I have learned that f2.8-f4 are my favorite apertures).

Some of the wide open shots of the 50 1.2 are really quite stunning, actually, but I feel it would be so hard to use that I would much prefer a lens that would allow me to actually get the shot.
01-30-2011, 08:50 PM   #86
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Well, here's a shot at f/1.2, where I wanted the shutter speed but didn't want any higher ISO. It isn't a great picture, and the bokeh doesn't really work in this type of shot, but I still like it. I would have needed a better high ISO camera to shoot it at f/2.8 or f/4. So, this was the lens that enabled me to get the shot.

01-31-2011, 01:31 AM   #87
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All one needs to "master" f1.2 shooting is decent VF, good split screen, lot of patience and huge amount of practice...

Battle between 2.8 and 1.2 is no win situation, you'll either get things slightly out of focus or you stand a good chance to have motion blur...
01-31-2011, 02:37 AM   #88
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Hmmmm//// All are almost the same
02-01-2011, 10:04 PM   #89
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I just posted a few more A50/1.2 vs FA31/1.8 test shots in this link.
02-02-2011, 01:24 AM   #90
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QuoteOriginally posted by Class A Quote
I'm pretty sure the f/1.2 lenses from Canon are sharper than the K50/1.2 wide open
I happen to own both,you're going to have to take my word for it but they are actually pretty damn close IMO. The Pentax holds the lead by having significantly lower PF than the canon lens, which suffers from it all the way to f/8
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