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08-05-2007, 10:25 AM   #1
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The need for "converting" focal lengths

When digital photography was new, there was a need to "convert" or compare focal lengths of 35mm format and the smaller sensors of digital. Now that digital is no longer a new idea, I really don't convert focal lengths anymore. When I have a 14mm lens on, that's super wide. My 21mm lens is my wide lens, and so on. I don't think, 14mm is kind of like 21mm on film, and my 21mm lens is like 32mm on film...

Just something I've noticed...

08-05-2007, 10:31 AM   #2
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QuoteOriginally posted by MikeH Quote
When digital photography was new, there was a need to "convert" or compare focal lengths of 35mm format and the smaller sensors of digital. Now that digital is no longer a new idea, I really don't convert focal lengths anymore. When I have a 14mm lens on, that's super wide. My 21mm lens is my wide lens, and so on. I don't think, 14mm is kind of like 21mm on film, and my 21mm lens is like 32mm on film...

Just something I've noticed...

You've simply acclimated yourself to the the tools you are using.

When I put my FA 35 f/2 on my K1000 the other day, my first comment was "wow, what a great field of view!". I put it back on my K100D and said, "that looks more normal now".

You're correct though, the thought process does adjust.
08-05-2007, 05:22 PM   #3
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I was just thinking this myself over the weekend. Although I still have to convert for my sister, who is still film, and my father. It's just a matter of time until we all get used to it, and until all the old filmies have converted.
08-05-2007, 06:02 PM   #4
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I agree, however the only thing is that with different SLR offerings (I'm talking beyond just Pentax) having different crop factors (1.0, 1.5, 1.6... etc), it's probably still beneficial to have a common frame of reference.... even one that's irrelevant to all of them for the purpose of discussion!

08-05-2007, 09:03 PM   #5
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And not just between brands -- Canon has different sensor sizes that all can take the same lenses. Nikon probably will shortly too, and who knows about Pentax. So, the common reference point probably still makes some sense.

On the other hand, maybe it's just better to talk about field of view in degrees.
08-05-2007, 10:17 PM   #6
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QuoteOriginally posted by bt*ist Quote
I agree, however the only thing is that with different SLR offerings (I'm talking beyond just Pentax) having different crop factors (1.0, 1.5, 1.6... etc), it's probably still beneficial to have a common frame of reference.... even one that's irrelevant to all of them for the purpose of discussion!

Exactly. This common frame of reference, and the fact that literally hundreds of millions of photographers around the world have a history with 35mm, is why the 35mm standard still remains a reference point.

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08-05-2007, 11:18 PM   #7
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QuoteOriginally posted by mattdm Quote
And not just between brands -- Canon has different sensor sizes that all can take the same lenses. Nikon probably will shortly too, and who knows about Pentax. So, the common reference point probably still makes some sense.

On the other hand, maybe it's just better to talk about field of view in degrees.
I agree with the latter point.

Remember, the focal length of the lens is what it is, regardless of what camera you put it on. 50mm = 50mm and is NEVER UNDER ANY CIRCUMSTANCES 75mm. It's the same lens on any camera. It's the SENSORS that are different and which account for different field of views. In my opinion, converting lens focal lengths to 35mm equivalents confuses as much as (or more than) it clarifies.

I never tell myself that my 200mm lens is "really" a 300mm or "equivalent to" a 300mm lens. I am aware that this lens behaves differently on my K10D than it would perform on, say, a K1000. But I don't blame that on the lens.

Will
08-06-2007, 12:03 PM   #8
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i am going to stay with film lenes i really do not care about the crop facter it has never bothered me or coused me cosern. what is it worth to me if i have all these nice lenes and they will not work on my K1000 becuse of a too small coverge area from digtal lenes

08-06-2007, 03:08 PM   #9
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QuoteOriginally posted by nathancombs Quote
i am going to stay with film lenes i really do not care about the crop facter it has never bothered me or coused me cosern. what is it worth to me if i have all these nice lenes and they will not work on my K1000 becuse of a too small coverge area from digtal lenes
That is a point not mentioned often. After many K1000 lens I now have two "Digital Only" kit lenses. They are not backward compatible, and won't be forward compatible if some day Pentax comes out with a KxD that has a 35 mm wide sensor. There may be some good bargains on "Digital Only" lenses.
08-06-2007, 08:16 PM   #10
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QuoteQuote:
On the other hand, maybe it's just better to talk about field of view in degrees.
I doubt 10% of the people know the FOV for a particular lens, me included. Most older photographers I'm sure think in focal length, not angle, as it has been the standard terminology for so long.
08-06-2007, 08:49 PM   #11
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QuoteOriginally posted by SpecialK Quote
I doubt 10% of the people know the FOV for a particular lens, me included. Most older photographers I'm sure think in focal length, not angle, as it has been the standard terminology for so long.
Yeah, I don't really think of FOV numerically. All I really care about is the focal length (the actual focal length, not the converted focal length) of the lens and the 'crop factor' of the camera.

In what way does it ever matter to know that a 50mm lens on a K10D "=" a 75mm lens on a 35mm film camera? There has never been a moment when I've had two camera bodies on hand, one digital, one film, and I've had to choose which one to put the lens on. I do of course need to know what result to expect from the lens when it's on the body that I'm using. But while the results may change, the focal length of the lens is the one constant here, which is why it makes me crazy for people to keep confusing the issue by trying to suggest that a 50mm is "really" 75mm. Much better to say that it's a 28-75 or 18-200 or whatever focal length lens used on this or that camera (or more precisely, with this or that sensor). That tells the story correctly.

There are some differences in the apparent depth of field calculations when the same lens is used with different sized sensors. I blogged about this a month ago.

Bottom line: I have a Tamron 28-75 lens. I use a Pentax K10D. I don't shoot with a 35mm film any more. I don't use the Nikon version of this lens on a camera with a 1.6x crop factor. I don't use a lens with these focal lengths on a four-thirds camera with a 2x crop factor. I know how this lens behaves on my camera. THAT ALONE IS WHAT MATTERS. I am aware that different cameras with different size sensor behave differently, but I don't blame that difference on the lens or use the lens as a way of explaining the differences -- since the lens has nothing to do with the differences whatever.

Will
08-06-2007, 09:14 PM   #12
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QuoteOriginally posted by LeoTaylor Quote
That is a point not mentioned often. After many K1000 lens I now have two "Digital Only" kit lenses. They are not backward compatible, and won't be forward compatible if some day Pentax comes out with a KxD that has a 35 mm wide sensor. There may be some good bargains on "Digital Only" lenses.
i agree lol Pentax needs to bring back there FA* lenes because i shore there is going to be a lot of people like me who are going to hedge there bets that in 10 or so yers there might be a FF in a pentax lol and like i sed befor i still wont to use my old camera

the hole covertion thing is a non issue
08-07-2007, 12:25 PM   #13
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QuoteOriginally posted by stewart_photo Quote
Exactly. This common frame of reference, and the fact that literally hundreds of millions of photographers around the world have a history with 35mm, is why the 35mm standard still remains a reference point.

stewart

Still, I think the point was that as shooters, most of us now think about what each lens does on our camera, without converting it to what the equivalent focal range is.
08-07-2007, 02:52 PM   #14
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QuoteOriginally posted by WMBP Quote
(snip) which is why it makes me crazy for people to keep confusing the issue by trying to suggest that a 50mm is "really" 75mm. (snip)

As you well know, photography has a very long history, the vast majority of it before digital cameras. For the many millions, like myself, who started in the 35mm era, that lens on a certain camera behaves much more like a traditional 75mm lens than a traditional 50mm lens. Therefore, as a frame of reference, it benefits some of us, myself included, to occasionally refer to that lens by it's 35mm equivalence. It also benefits some of us to refer to 35mm equivalence when discussing a particular lens with someone using another camera brand. Of course, you're obviously free to have a different perspective and entirely ignore those references. What I don't understand is why others referring to the 35mm equivalence would drive YOU crazy, or why anyone (some in this thread) would be upset enough about it to rant in a photography forum.


QuoteQuote:
(snip) but I don't blame that (snip)

I ignored this the first time you wrote it, but I don't understand you repeated references to "blame." I've never seen anyone attempt to assign "blame" to this, or anything related to it. Therefore, I don't understand what you're talking about, Will. And, since I'm venting on your messages, let me also add that we're not stupid either. We know that a 50mm lens is a 50mm lens, therefore don't really need to be lectured about it. What we're referring to is it's 35mm equivalence, a reference point that is familiar and comfortable to at least some of us in certain circumstances.

stewart
08-07-2007, 03:30 PM   #15
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QuoteOriginally posted by mcleoud151 Quote
Still, I think the point was that as shooters, most of us now think about what each lens does on our camera, without converting it to what the equivalent focal range is.

I don't see anything limiting the discussion solely to us as "shooters." I doubt most care what others think about focal length while shooting. In fact, I doubt most, without cause (flash calculations or whatever), even pay that much attention to focal length (actual, converted, or other) while shooting. Regardless, the followup comments certainly seem more inclusive. Some here appear almost bothered by constant references to 35mm. However, that 35mm frame of reference is going to remain as long as different sensors remain and lenses continue to behave differently with those sensors.

stewart
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