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02-13-2012, 08:52 PM   #76
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QuoteOriginally posted by alohadave Quote
Well, if you look at full frame, the diagonal is 43.2mm, yet the normal lens has been 50 and 55 at various times.
50-55-58mm lenses were standard on some FF SLRs and various other cams. So were 35-37-40-43-45mm lenses. That makes them common-normal, not optical-normal. I don't remember if it was in this thread or another, but I recently listed a number of definitions of 'normal'. Linguistics, optics, statistics, medicine, geometry, sociology, common usage, all have very different impacts.

'Theory' has a similar wide range of usages, including "extrapolation" (philosophy) and "a workable model supported by the preponderance of data" (science) and "it could have happened this way" (law) and "wild-ass guess" (popular). Queer theory and quantum theory and quiz-show theory are quite different.

No, in optics, 'normal' has a specific technical definition: frame diagonal. 50-55-58mm are not optically normal on an FF camera. Did you notice the first lens that was released with the 645D? Is was 55mm, which is precisely 'normal' for that camera's 33x44mm frame.

02-13-2012, 09:14 PM   #77
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QuoteOriginally posted by Jonathan Mac Quote
50, 55 & 58mm lenses were considered standard on film. 50mm was usually the minimum for a standard lens.
Unless, of course, you were shooting with one of the many 35mm fixed lens rangefinder cameras where 40mm-45mm was pretty much the norm.


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02-13-2012, 09:21 PM   #78
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Konicas came with a 40mm pancake lens in the TC/FS-1 era.
02-13-2012, 09:53 PM   #79
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QuoteOriginally posted by RioRico Quote
I have a nice pancake Chinon 45/2.8 and a big fat K50/1.2, both in PK-M mount. I have FF rangefinders with 45mm f/1.7 and f/1.8 lenses. I have never seen a 45/1.4 nor 45/1.2 for FF SLRs. I am very sure that fast 50-55-58mm lenses were made because they COULD be made, whilst 40-43-45mm lenses that fast weren't made because they COULDN'T be made, especially to clear an SLR mirrorbox, not and be commercially viable.

Back in film days, FF cameras were shipped with lenses ranging from 35-58mm. That's quite a 'normal' range. HF (half-frame, ~APS-C size) cameras shipped with lenses in the 24-40mm range (FOV equivalent to 35-60mm on FF), sometimes longer. But for non-SLRs, shorter optics predominated. And for FF SLRs, IIRC fast 58s predated fast 55s and 50s; fast 50s came to rule the field. That was the evolution: get shorter and faster.
Just so we're on the same page, when you say "FF" you mean 35mm, right? Just a little confused because when talking about film the term "full frame" doesn't make any sense. 35mm should be called by its proper name, a miniature format!

02-14-2012, 03:19 AM   #80
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QuoteOriginally posted by isaacc7 Quote
Just so we're on the same page, when you say "FF" you mean 35mm, right? Just a little confused because when talking about film the term "full frame" doesn't make any sense. 35mm should be called by its proper name, a miniature format!
That's right, all 35mm film formats are 'miniature' but we don't call them MF because that's already taken (a few times). UAW/MF!

Moving through the web of formats is dizzying. It all started when Tom Edison ordered cine stock from George Eastman, specified as 70mm wide. Eastman cut it in half and thus came 35mm film, also originally for cinema. Those early cine frames, disregarding sprocket holes etc, grabbed 24x18mm images. This was "single-frame". The earliest still cameras using that film were single-frame. Bannock/Leica built a double-frame camera, in the 36x24mm format we now misleadingly call FULL-FRAME.

Other formats also parsed 35mm-wide film, but we'll skip those Robots and panos now. Suffice that when I say FF or 135/FF, I mean a 36x24mm double-frame. HF or 135/HF (half-frame) is the old cine 24x18mm format, very very close to nominal APS-C. Is FF an accurate term? No, but it's been in common use for a long long time, so we might as well live with it.
02-14-2012, 12:39 PM   #81
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QuoteOriginally posted by isaacc7 Quote
Just so we're on the same page, when you say "FF" you mean 35mm, right? Just a little confused because when talking about film the term "full frame" doesn't make any sense. 35mm should be called by its proper name, a miniature format!
If you want to get pedantic, call 35mm by Kodak's film name, 135. That gets confusing though because people think you are talking about a 135mm lens an wonder why you bring a focal length into a frame size debate.

It's just an utter mess no matter how you address it.
02-14-2012, 01:16 PM   #82
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QuoteOriginally posted by alohadave Quote
It's just an utter mess no matter how you address it.
Back when I diddled with digital and analog electronics, we had a saying: The great thing about standards is that there are so many of them (re: interfaces, protocols, etc.) I see something similar in photography, except mostly without standards-enforcement organizations. So we have a mix of corporate nomenclature, popular usage, PR-speak, legacy terminology, neologisms, a great mish-mash -- and that's just in Anglish, which isn't a straightforward technical language. (At least it beats COBOL.)

I try to bypass some of this by usually referring to certain film standards as 135/FF or 135/HF (half-frame, about the same size as APS-C). At least those standards are fixed, unlike APS-C, which has a nominal value, and various different implementation values. (My K20D's sensor has a diagonal of 28.1mm, not the APS-C 30/1mm.) Would help if formats (film or digital) used different measurement units than lenses, so we wouldn't confuse 35-70-120-135 lenses with film -- Kodak should have prefixed their film numbers with K or E or A or something.

But what does FF mean? Full-frame (35x24mm) or Fast Forward or Front-Focus or Flying F*chhead or what? Is MF Medium-Format or Miniature-Format or Manual Focus or M***erF***er or what? Do we need both FOV and AOV? (AOV is numeric, FOV is conceptual.) Do we need both 2x and 2:1 to describe magnification -- and how do we readily distinguish magnification from enlargement? And if a lens is labeled APO, is it *really* apochromatic?

PentaxForums functions as an endless seminar on subjects photographic. Learning photography also requires learning the jargon. So our discussions here constitute a continuing language lesson, to both learn and refine the jargon. Forget about crap.factors and equivalents -- except when they're useful or necessary. Forget what you think 'normal' means because it may mean something else. To master a lens, learn to see like a lens, not like an awestruck tourist gazing upon beauty. All this is part of learning photography. I've been at it for over 5 decades and there's still more than I can ever learn. May it never end!
02-14-2012, 01:35 PM   #83
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QuoteOriginally posted by isaacc7 Quote
Just so we're on the same page, when you say "FF" you mean 35mm, right? Just a little confused because when talking about film the term "full frame" doesn't make any sense. 35mm should be called by its proper name, a miniature format!
Unless, of course, we are talking half-frame or pano-35...


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02-14-2012, 01:53 PM   #84
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QuoteOriginally posted by westmill Quote
I understand prints can be used yes...... not that they are nesercary or rellivent NO....
Actually yes. I think you have the term "perspective distortion" confused with the more ordinary sense of the word "perspective", but that more ordinary sense is not relevant to a discussion of what is "normal" about a lens. All lenses have *exactly* the same perspective, since perspective is a function only of where you are positioned, not anything about focal length. But focal length does effect angle of view, and *when considered along with the angle subtended by a print made from the image and viewed from a given distance*, that is when we can start talking about perspective distortion.

I realize you are not interested in learning more about this, but for others following the discussion:

The sense in which focal length relates to perspective is with respect to the perspective distortion that results when you print the image or oherwise display it in tangible form. A printed or displayed image is free from perspective distortion if the angle subtended by the print itself as viewed from a given position is the same as the angle of view depicted within the image. In other words, if you can hold up the print at a given viewing distance and all objects within it appear the same size as they would have in the scene itself, then the image is free from perspective distortion for that size print at that viewing distance. If on the other hand objects appear larger or smaller in the print when viewed from a given distance, that image is said to exhibit perspective distortion for that particular print size and viewing distance. It stands to reason that this dependent as much on the print size and the viewing distance as it is on the lens used. A print of an image taken with a telepjoto lens will be free from perspective distortion if you view it from far enough away, and a pront of an image from a wide angle lens will be free from perspective distortion if you view it from close enough.

What makes a lens/camera combination "normal" in this sense is if the angle of view it captures matches the angle subtended by "typical" sizes of prints viewed from "typical" distances. Since obviously the terms "typical" here are pretty subjective, it follows that there is no scientific formula for determining *exactly* what focal length will be "normal" in this sense. But it does happen to be true that a focal length eqaul to the sensor diagonal gives you an angle view that is in the ballpark of the sorts of angles subtended by typical print sizes viewed from typical distances. Supposedly, that's because a typical viewing distance for a print does happen to be the length of the diagonal of the print. But I'm not sure that's really the case, or that the mathematics really works out quite like that.
02-14-2012, 02:07 PM   #85
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QuoteOriginally posted by Marc Sabatella Quote
Supposedly, that's because a typical viewing distance for a print does happen to be the length of the diagonal of the print. But I'm not sure that's really the case, or that the mathematics really works out quite like that.
With "normal" vision, the closest viewing distance is 25cm.
That's the diagonal of a 15x20cm print.
02-14-2012, 02:20 PM   #86
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QuoteOriginally posted by Marc Sabatella Quote
Actually yes. I think you have the term "perspective distortion" confused with the more ordinary sense of the word "perspective", but that more ordinary sense is not relevant to a discussion of what is "normal" about a lens. All lenses have *exactly* the same perspective, since perspective is a function only of where you are positioned, not anything about focal length. But focal length does effect angle of view, and *when considered along with the angle subtended by a print made from the image and viewed from a given distance*, that is when we can start talking about perspective distortion.

I realize you are not interested in learning more about this, but for others following the discussion:

The sense in which focal length relates to perspective is with respect to the perspective distortion that results when you print the image or oherwise display it in tangible form. A printed or displayed image is free from perspective distortion if the angle subtended by the print itself as viewed from a given position is the same as the angle of view depicted within the image. In other words, if you can hold up the print at a given viewing distance and all objects within it appear the same size as they would have in the scene itself, then the image is free from perspective distortion for that size print at that viewing distance. If on the other hand objects appear larger or smaller in the print when viewed from a given distance, that image is said to exhibit perspective distortion for that particular print size and viewing distance. It stands to reason that this dependent as much on the print size and the viewing distance as it is on the lens used. A print of an image taken with a telepjoto lens will be free from perspective distortion if you view it from far enough away, and a pront of an image from a wide angle lens will be free from perspective distortion if you view it from close enough.

What makes a lens/camera combination "normal" in this sense is if the angle of view it captures matches the angle subtended by "typical" sizes of prints viewed from "typical" distances. Since obviously the terms "typical" here are pretty subjective, it follows that there is no scientific formula for determining *exactly* what focal length will be "normal" in this sense. But it does happen to be true that a focal length eqaul to the sensor diagonal gives you an angle view that is in the ballpark of the sorts of angles subtended by typical print sizes viewed from typical distances. Supposedly, that's because a typical viewing distance for a print does happen to be the length of the diagonal of the print. But I'm not sure that's really the case, or that the mathematics really works out quite like that.
Then why do you insist on quoting me ?
If you have a point of veiw thats fine with me, Its a forum after all.
If i dont want to learn you say.... such arrogance !
Doesnt deserve a response !
02-14-2012, 02:52 PM   #87
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QuoteOriginally posted by stevebrot Quote
Unless, of course, we are talking half-frame or pano-35...
Or square-frame or other aspects (like the early Leica 34x24mm), or the various (many!) 35mm cine formats, or variants like 126 (35mm wide but with only one perforation row), or when I shoot sprocket-hole photography by inserting a 135 cart into an MF camera. Film formats are almost as complex as sex|gender roles|practices. Yeah, pretty f*cked...

Back to APS-C: I see at least 6 different sensor sizes labeled APS-C with diagonals ranging from ~26-30+mm -- and that doesn't count APS-H at 34mm.

I try to keep track of formats, a sick hobby. On my info spreadsheet, I have about 100 different digital and (non-cine) film formats listed. I have no idea how many formats have existed in total, nor can I guess how many digital formats will be constructed in the near-to-far future. The situation will NOT get any simpler. But read a bit on the history of film -- it's revelatory and entertaining!

ObTopic: Each of those formats has its own 'normal' focal length. And the 'standard' lens(es) shipped with cameras using those formats may or may not be somewhat close to the 'normal' dimension. Imagine a K5 shipped with a 24mm or 75mm as the kit lens? Some 135/HF cameras were so equipped. With the various APS-C sensors I mentioned above, 'normal' is somewhere between 25-31mm, and standard lenses (based on prior industry practice) might be in the 21-35mm range.

Conclusion: Normal is normal, but standards are ever-flexible. Live with it!
02-14-2012, 03:43 PM   #88
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When I was shooting with film all my 35mm SLR used the 50mm as a standard lens My Bronica 645 Etrs used a 75mm standard which was equivelent to a 50
feild of veiw as was my bronica RF645 but my Mamiya RZ67 came with a choice of two standard lenses. Either the 90mm which gave an angle of veiw 44mm
or the 110mm which gave a 53mm angle of veiw. I chose the latter because I used it mostly in the studio for potraits.
I often thought I wished I had bought the wider standard though, since because of the big neg it gave plenty of scope for cropping
but you cant crop backwards to gain wide angle. This way of thinking played a role in my choice of the tamron 17-50 on the K5.
It produces enough resolution to crop if I need more zoom !
02-15-2012, 07:50 AM   #89
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QuoteOriginally posted by NotaxPen Quote
What is Pentax's obsession with the nearly useless 40mm focal length? It's too long for a standard and too short for a tele. OK, it's real small and cute. I bought it.

Why can't they make a "Proper" normal lens for the cropped aps sensor? FA43 /1.5 crop factor = 28mm.
They need a 28mm in either the DA Limited pancake style (Small/compact) or/and a DA* style (Fast/full-featured)
You are absolutely right. Pentax does not offer a decent solution in the 30-35 mm league designed for APS-C sensors. The FA31 is a nice lens, but completely over-engineered for this format. It is just f/1.8! 40 mm and all it's derivatives are nice, but do not cover a classic angle of view.
As long as people assume that the FA31 is the high speed normal lens in Pentax land, Pentax has no reason to change it's attitude - the 1.8/50 in the roadmap is a slap in the face. The 2.4/35 is dead cheap as someone pointed out. Well, one would expect a much larger aperture here. Besides the 55 mm lens (maybe the FA77) there is no large apeture lens in Pentax land, only the 55 was designed recently for DA mount with modern features (coating, AF, ...) - the 43 do not qualify for the given angle of view. For APS-C the FA31 is not really a large apeture lens. During FA times and full frame film cameras there were a 2/24 and 1.8/31 mm wide angle, the 1.4 and 50 mm normal lens, and the 1.4/85 and 1.8/77. Here the FA31 represents a large aperture wide angle, while the 1.8/50, 1.9/43 could be considered standard. You can match the FA85/77 with the DA55 in APS-C land, there are no matches for the FA24/31/50 available right now and no decent matches for any 50 mm lens, neither at f/1.4 nor at f1.8, not even at f/2.
People will probably not buy large quantaties of large aperture primes anymore, although they keep buying FA31/43/77 lenes. It is less expensive for Pentax to sell FA31/43/77 mm lenses rather than designing new lenses. The same probably holds for the announced 1.8/50 easy to make from old optical calculations, just make one, people will buy it. A DA30/1.4 would be much less expensive than the current FA31. Sigma makes such a lens, another reason for Pentax not to make one. A 21 or 24 mm large aperture prime is missing as well, the 3.2/21 is designed for size, not for anything like a large apeture. Pentax pumped out so many small aperture primes that people think a 2.4/35 is a larger aperture lens. The only more or less genuine lens announced is the 560 mm, probably just a trade off between a really fast 600 mm lens and a slow f/8 solution. Pentax is sitting on the brake regarding new innovative lens designs. At the same time they present more and more replicates of old formulas.

Last edited by zapp; 02-15-2012 at 07:58 AM.
02-15-2012, 10:00 AM   #90
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QuoteOriginally posted by zapp Quote
Pentax does not offer a decent solution in the 30-35 mm league designed for APS-C sensors.
As a very satisfied user of the DA 35 Macro Ltd, I strongly disagree!
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