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06-01-2013, 02:39 PM   #1
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40mm is "normal"

I know there's a lot of math that goes into accounting for crop factor and field of view between film and digital and traditionally what was considered a "normal prime", but I've noticed that what I capture with my 35mm lens is smaller than how it appeared to my eye. I put an SMC-M 40 on my K5 today (didn't belong to me and I gave it back) and what appeared in my LCD looked the same as what I saw with my eyes standing on that same spot, at least from a perspective perspective. My peripheral vision is of course much wider than my sensor..or film.

I hear mathematical explanations for "normal", that I can't dispute (I'm a bear of very little brain), but in layman's terms, my own experience tells me that it's 40mm. Sorry, I'm sure this is a well known fact, but I thought someone might benefit from reading this.

It kind of made me want a 40/2.8 ltd too. I always sort of winced at the idea of a pancake lens, but it looked and felt quite good on there in the flesh. The M 40 doesn't get much love in our review section, but the contemporary version does.

06-01-2013, 02:57 PM   #2
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It doesn´t really matter for the point you are trying to make, but the viewfinder´s magnification (0,92x for the K-5 when using 50mm lens) also comes into play when trying to get the same perspective and scale with the camera than with the naked eye.
06-01-2013, 02:58 PM   #3
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I agree. I think 40-50mm is as close to normal vision as you get, in terms of how big objects are and how far they appear to be. This ignores the actual field of view, though, which apparently is more important to a lot of people. Of, course, viewfinder plays a role as well.
I am really enjoying my 40mm XS recently, even though I didn't like it as much as I first got it (because its only f2.8, has an odd filter size, and its not perfect wide open). But its focuses quickly, its compact so you can carry it with you anywhere, and its very sharp, with very little distortion (unlike the DA 35mm f2.4)
06-01-2013, 02:59 PM   #4
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QuoteOriginally posted by troika Quote
I hear mathematical explanations for "normal", that I can't dispute (I'm a bear of very little brain), but in layman's terms, my own experience tells me that it's 40mm. Sorry, I'm sure this is a well known fact, but I thought someone might benefit from reading this.
Well, the math assumes that 50mm is considered a normal lens on fullframe. The focal length that provides the same level of magnification on APS-C is 50 / 1.5 = 33 1/3mm, and 35mm is close to that. But, you may not consider 50mm a normal lens on fullframe, and there's nothing wrong with that. If experience taught you that 40mm on APS-C is a normal lens, then I would think you will find 60mm a normal length on fullframe (given that nothing else changes).

In other words, the math still applies. But the math doesn't say what FOV you should think of as normal.

Besides, there are other factors too. The viewfinder coverage and level of magnification, how close your eye is to the viewfinder, etc.


Last edited by starbase218; 06-01-2013 at 03:05 PM.
06-01-2013, 03:11 PM   #5
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Well, I agree that 33 1/3 is normal for LPs, which I still have plenty of.

Again, I assume everyone here has much more experience than I do in this field of study and I'm not trying to argue or dispute anything.

Taking pictures with my 35 and my 50 I get good results but neither seems to give the perspective that I got standing on that spot and looking at that subject. The 50 makes it appear that I was closer than I actually was, the 35 makes it appear that I bit farther back. With the 40 I tested today, looking at the LCD of the photo and looking over the camera at what I photographed, they looked the same to me. For whatever that's worth.

Last edited by troika; 06-01-2013 at 06:43 PM. Reason: Farther/further
06-01-2013, 03:52 PM   #6
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50mm is only normal on 135 Ff because that is what Oskar Barnack decided it should be. A 50mm lens was easier to design than a 43mm. Normal on APS-C is 30mm.
06-01-2013, 03:53 PM   #7
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QuoteOriginally posted by troika Quote
Well, I agree that 33 1/3 is normal for LPs, which I still have plenty of.

Again, I assume everyone here has much more experience than I do in this field of study and I'm not trying to argue or dispute anything.

Taking pictures with my 35 and my 50 I get good results but neither seems to give the perspective that I got standing on that spot and looking at that subject. The 50 makes it appear that I was closer than I actually was, the 35 makes it appear that I bit further back. With the 40 I tested today, looking at the LCD of the photo and looking over the camera at what I photographed, they looked the same to me. For whatever that's worth.
Go for the FA 43. You will not be disappointed!
06-01-2013, 04:11 PM   #8
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QuoteOriginally posted by troika Quote
Well, I agree that 33 1/3 is normal for LPs, which I still have plenty of.
Lol - it took a minute for me to realize what you meant. But my Technics SL-1200 II also has a 33 1/3 setting. Smaller singles usually run at 45 rpm. Is this the APS-C of the turntable world?

06-01-2013, 04:12 PM   #9
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@ Na Horuk - Seems you have a bad copy of the DA 35/2.4 . Mine has very little distortion of any kind.

Jack
06-01-2013, 05:34 PM   #10
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The "standard" or "normal" focal length that gives a similar field of view to that of the human eye is between 43-58mm depending on who you ask. For 35mm film (24mm by 36mm), the diagonal measurement is 43.27mm. That is why the FA43 was designed at its precise focal length and why 50's, 55's, and even 58's were made commonly back in the film era. 40mm on the APS-C would be at the high end of that range and a wee bit past it. 28mm to 35mm put you in the more typical range for "normal" on APS-C.

Last edited by Docrwm; 06-01-2013 at 05:39 PM.
06-01-2013, 05:54 PM   #11
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I think we may all focus on a different part of our physical field of view. when i ben in photography, a 28mm was extremely natural for mwto use. it took me a long time to be able to shoot with a 50mm -the field of view was too telephoto, and it just didnt make sense to me. i didnt see things the way my 50mm presented them. So i consider "normal" to be a very misleading term..
06-01-2013, 06:24 PM   #12
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My preference in film is my M 40mm f/2.8, 50 seemed a bit long and 35 a bit wide (although I've only recently acquired a 35 and maybe haven't given it a chance yet). On APS-C I prefer 28.
06-01-2013, 06:33 PM   #13
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QuoteOriginally posted by Docrwm Quote
The "standard" or "normal" focal length that gives a similar field of view to that of the human eye is between 43-58mm depending on who you ask. For 35mm film (24mm by 36mm), the diagonal measurement is 43.27mm. That is why the FA43 was designed at its precise focal length and why 50's, 55's, and even 58's were made commonly back in the film era. 40mm on the APS-C would be at the high end of that range and a wee bit past it. 28mm to 35mm put you in the more typical range for "normal" on APS-C.

This is what makes me wonder why there isn't a Pentax ~28mm DA "normal". I know the various 35s fill that role, but I would kill for a DA* 28/2 or Limited 28/2.8! I know I'm not the first to say that.

To the OP, I recently acquired an M40 and agree, it is a nice lens on APS-C. However, I like its FOV better on my film bodies, which is why I want that 28!
06-01-2013, 07:46 PM   #14
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QuoteOriginally posted by filoxophy Quote
This is what makes me wonder why there isn't a Pentax ~28mm DA "normal". I know the various 35s fill that role, but I would kill for a DA* 28/2 or Limited 28/2.8! I know I'm not the first to say that.

To the OP, I recently acquired an M40 and agree, it is a nice lens on APS-C. However, I like its FOV better on my film bodies, which is why I want that 28!
28 is a logical addition to the range. We have 15-21-31-35-40-43-50-55-70-77 with all but the 50 & 55 being limiteds. A 28 would be a nice addition and they have several very nice ones in the old lineup.
06-01-2013, 07:59 PM   #15
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QuoteOriginally posted by Docrwm Quote
28 is a logical addition to the range. We have 15-21-31-35-40-43-50-55-70-77 with all but the 50 & 55 being limiteds. A 28 would be a nice addition and they have several very nice ones in the old lineup.
Or... just get a zoom (say, 18-55, or 16-45) and use tape to hold it at your preferred FL (say, 28mm), then fire away...

Easy... Peasy... M
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