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06-03-2013, 07:42 AM   #1921
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QuoteOriginally posted by Fogel70 Quote
Except for complete newbies, I have never heard of anyone believing a lens change focal length depending on sensor size.
Except Olympus. I have a 4/3 long zoom somewhere that has the focal length stamped but the adjusted focal length on a sticker.

06-03-2013, 08:14 AM   #1922
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QuoteOriginally posted by VoiceOfReason Quote
When I was a complete newb people on another forum led me to believe that a 20mm lens was really a 30mm lens on ASPC (I was looking at the Sigma 30 f/1.4 and the Sigma 20 f/1.8) unless the lens was made specifically for ASPC, then it would be the focal length advertized. So, I was led to believe the Sigma 20mm f/1.8 (works for full frame) would give me the EXACT same FOV that the Sigma 30mm f/1.4. Yeah, I actually believed it at the time. Thankfully I'm older and wiser now!
Yeah, this kind of story is very familiar to me. I was lucky to learn the basics from books, before this nonsense started; but I saw experienced people explaining this BS to beginners, which were falling in this trap.
They weren't able to say what's the focal length of a 50mm lens, when it's unmounted - or why wouldn't they compute the BS equivalent if cropping on a computer.
06-03-2013, 10:04 AM   #1923
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QuoteOriginally posted by VoiceOfReason Quote
When I was a complete newb people on another forum led me to believe that a 20mm lens was really a 30mm lens on ASPC (I was looking at the Sigma 30 f/1.4 and the Sigma 20 f/1.8) unless the lens was made specifically for ASPC, then it would be the focal length advertized. So, I was led to believe the Sigma 20mm f/1.8 (works for full frame) would give me the EXACT same FOV that the Sigma 30mm f/1.4. Yeah, I actually believed it at the time. Thankfully I'm older and wiser now!
You were not alone. The camera makers sold APS-C cameras as increasing focal length. This was even quoted in books like Scott Kelby's digital photography series. There was even a reviewer who got into a big flame war with Pentaxians over his perception of the difference between the FA limiteds/DA limiteds -- somehow believing that the DA limiteds 40mm was different from the FA limited 43mm.
06-03-2013, 10:46 AM   #1924
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QuoteOriginally posted by Kunzite Quote
Photography as a craft is doomed, replaced by pseudo-science - because people who should know better are helping with this nonsense.
But so far, these sites only mention the BS focal and BS aperture, fortunately the lenses being appropriately named.
Don't worry, there are a whole mess of good photographers out there taking some great photos right now that don't have the time to get involved in these technical discussion. The world is a much bigger place than online forums.

06-03-2013, 11:04 AM   #1925
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QuoteOriginally posted by johnmflores Quote
PentaxForums - Where every day is the zombie apocalypse.
LOL.....
06-03-2013, 02:07 PM   #1926
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QuoteOriginally posted by derekkite Quote
Except Olympus. I have a 4/3 long zoom somewhere that has the focal length stamped but the adjusted focal length on a sticker.
Doesn't the sticker include the word "equivalent" or something similar. I think every manufacturer still use "equivalent focal length" in their marketing. I can imagine Ricoh having some troubles in marketing on 5-15mm and 16-56mm lensor without using equivalence in describing them.


There is no doubt that there has been BS in the past (or more of a problem in finding the correct terms for explaining things) and some probably tried to oversimplify things, but was it not quite long ago since people used terms like "focal length multiplier" to explain "crop factor". But things like this can probably be found with every new tech.

In the future we might use FOV and "aperture size" instead of focal length and f-number to explain lenses, and use "exposure time" and "noise ratio" instead of shutter speed and ISO. Then we might not even care about sensor size or megapixels. Then we might laugh about how silly we where back in 2013.
06-03-2013, 02:26 PM   #1927
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QuoteOriginally posted by Fogel70 Quote
use "noise ratio" instead of ISO.
Well we do need a figure to compute exposures.

However, given recent developments,
I do think the ISO made a mistake
when they adopted the arithmetic ASA scale
instead of the logarithmic DIN scale.

Tri-X used to be 27 DIN or 400 ASA/ISO, which wasn't too bad.
But 39 DIN is better than 6400 ASA/ISO,
and 42 DIN is way better than 12800 ISO.

That little green window on top is getting crowded!
06-03-2013, 02:50 PM   #1928
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QuoteOriginally posted by lytrytyr Quote
Well we do need a figure to compute exposures.

However, given recent developments,
I do think the ISO made a mistake
when they adopted the arithmetic ASA scale
instead of the logarithmic DIN scale.

Tri-X used to be 27 DIN or 400 ASA/ISO, which wasn't too bad.
But 39 DIN is better than 6400 ASA/ISO,
and 42 DIN is way better than 12800 ISO.

That little green window on top is getting crowded!
very little people get the logarithmic sale

06-03-2013, 02:56 PM   #1929
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QuoteOriginally posted by dankoBanana Quote
very little people get the logarithmic sale
Midgets?
06-03-2013, 03:00 PM   #1930
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QuoteOriginally posted by jcdoss Quote
Midgets?
thats insulting. They are height challenged
06-03-2013, 03:18 PM   #1931
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QuoteOriginally posted by Fogel70 Quote
"focal length multiplier" to explain "crop factor"
Heck, I remember people telling me that I was unfairly denigrating APS-C by calling it a 'crop factor'.
06-03-2013, 03:22 PM   #1932
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QuoteOriginally posted by dankoBanana Quote
very little people get the logarithmic sale
The f-stop scheme is logarithmic.
06-03-2013, 03:44 PM - 2 Likes   #1933
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Really people, I cannot but wonder. I thought this forum had evolved into a more mature one. My bad.

Equivalence is a theorem, not a belief, religion, argument or opinion. As such, it needs to be taught to newbies not knowing it yet.

The fact that normalizing 1. focal length, 2. fstop, 3. iso leads to a specification of a photo's capture parameters which are entirely independent of sensor size (i.e., the sensor size cannot be deduced from the resulting photo's properties, even if you look at noise or diffraction or bokeh or other artefacts) is a surprising yet fundamental truth which any knowledgeable photographer needs to know and to use in a discussion involving more than one sensor size. It is now a textbook content for any lecture on photography. Just like fstop is.

As such, it isn't trivial at all. To many, it comes as a surprise so big that they can't understand it. It isn't clear a priori that the equivalence normalization has this property. After all, e.g. if you look at "depth of field" formulae, it seems to depend on focal lengths and image circle diameters ... Equivalence is the beautiful theorem that it and any other optical property doesn't upon closer inspection. I.e., a camera can be specified 100% without specifying its image circle.

All this debate just obfuscates this simple to state yet powerful and therefore inherently beautiful truth. It is driving me nuts if I see people trample on beauty.

I'll leave this topic alone now (in this thread). I only contribute to few threads on PF anymore nowadays. The experience in this thread wasn't a rewarding one. Anyway, the topic was K-3, right?

Last edited by Ash; 06-04-2013 at 05:10 AM.
06-03-2013, 06:28 PM   #1934
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QuoteOriginally posted by ElJamoquio Quote
What features do you find clearly different between the K-30 and K-5II?

For what it's worth, I would argue that the myriad of people coming in and asking 'K-30 or K-5/K-5II?' would indicate it's not completely nonsensical to consider those models as partially (or largely) overlapping.

You agree with Pentax, which is fine and I won't try to convince you otherwise. In my opinion, there hasn't been a model worthy of 'new' since the K-5. They're long overdue for a model with clearly differentiated features, and I agree with you that a new model will likely be announced this year.
Nikon types write in and say 5200 or 7100 too. That doesn't mean they're the same camera.

As for new - wow, you seem to be saying that unless it has a new sensor then its not a new camera model. Processor upgrades, AF upgrades, improvements in low light focus and performance, addition of an f2.8 sensor, introduction of the K-01 (whatever you think of it), Q & Q10 - weren't those all done after the K-5 was released?
06-03-2013, 06:30 PM   #1935
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QuoteOriginally posted by johnmflores Quote
Don't worry, there are a whole mess of good photographers out there taking some great photos right now that don't have the time to get involved in these technical discussion. The world is a much bigger place than online forums.
Yes, there are also wonderful blogs.
Thanks.
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