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FORUMS Canon Cameras, Lenses & Accessories Canon EF and EF-S Lenses 
Thread started 10 Feb 2009 (Tuesday) 10:09
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Question on EF vs. EF-S

 
WT21
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Feb 10, 2009 19:01 |  #16

SkipD wrote in post #7298565 (external link)
There are two portios of your question that I would like to address.

First of all, and more to the basic point of your question, there is absolutely no difference in field of view on an APS-C format camera (the so-called "crop" format) between an EF lens and an EF-S lens set to the same focal length. An EF 50mm lens, for example, will provide exactly the same framing, field of view, and depth of field as an EF-S lens adjusted to 50mm and set for the same aperture.

Secondly - the part I put in bold in your quote above is wrong. You do NOT have to multiply the focal length by anything. Please read the next few paragraphs to understand.

The "crop factor" has only one valid use. Here's an example: Joe took a photo of Mount Rushmore with a 35mm camera from a particular place using a 200mm lens. You want to replicate that photo with your Rebel XTi. What focal length do you need to do that from the same location that he took his photo? Divide the 200mm by 1.6 and you get the answer - 125mm. The "crop factor" is a REFERENCE between the two formats that lets you compare the field of view of particular focal lengths between the two formats.

The "crop factor" (related to using lenses essentially designed for 35mm SLR cameras) is always given assuming that the 35mm format (24x36mm) is the reference master. Something to realize, though, is that the 35mm film format is not, never has been, and never will be the "master" format against which all other camera formats are referenced. It is simply the format of the cameras that have also evolved into today's commonly used digital SLRs.

If you do not have significant experience with 35mm film SLR cameras, you can virtually forget the "crop factor". All you really need to know is that a "normal" focal length for the APS-C format is approximately 30mm. Any focal length shorter than 30mm is considered wide-angle and anything longer than 30mm is a "telephoto" (technically the wrong use of the word, but it's commonly used for a lens longer than "normal").

I hope this all helps clear up the mud.

I disagree. Photo sites and references talk in 35mm equivalencies all the time, especially at the beginner level. The 35mm FOV equivalences are very important to understand, so when you buy a 50mm lens, when you read somewhere that 50mm was a "normal" lens, you aren't surprised by why people seem so close in the viewfinder.


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xarqi
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Feb 10, 2009 19:04 |  #17

WT21 wrote in post #7299075 (external link)
I disagree. Photo sites and references talk in 35mm equivalencies all the time, especially at the beginner level...

... and thereby engender exactly the confusion that SkipD and Wilt are trying to redress.




  
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WT21
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Feb 10, 2009 19:07 |  #18

xarqi wrote in post #7299107 (external link)
... and thereby engender exactly the confusion that SkipD and Wilt are trying to redress.

SkipD and Wilt cannot redress it. Two people against a massive industry? Get real. It's misleading and not helpful to tell newbies to forget it, though explaining it is helpful.

Might as well be the boy with your finger in a dike. Also, it is not a bad thing to have reference standards in technology. Or, could someone explain to me why it is a bad thing.


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SkipD
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Feb 10, 2009 19:07 |  #19

WT21 wrote in post #7299075 (external link)
I disagree. Photo sites and references talk in 35mm equivalencies all the time, especially at the beginner level. The 35mm FOV equivalences are very important to understand, so when you buy a 50mm lens, when you read somewhere that 50mm was a "normal" lens, you aren't surprised by why people seem so close in the viewfinder.

The problem is that those sources of information are confusing the heck out of new photographers. There are so many incorrect beliefs that folks apparently get from those sources that those of who do the teaching here a lot try to get the newbies to regroup and rethink the truths without all the bunk.

For example, 50mm lens is not a "normal" focal length for any other format than the 35mm film format (using the 24mm by 36mm film frame). However, many newbies do their reading and seem to be stuck on the idea that a 50mm lens has a magic perspective about it and should be the ideal lens for any format camera.


Skip Douglas
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phigment
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Feb 10, 2009 19:09 |  #20

Yes, all lenses mounted on a crop body still need to be multiplied by the crop factor to get the same field of view as on a full frame. But this doesn't account for other factors such as depth of field and perspective.

Wilt wrote in post #7298999 (external link)
Science has made inferior genetics into viable people. It makes one think...the gene pool is becoming contaminated by the genetically inferior.

I don't in the least advocate the practices started by Adolf and the Gestapo 60+ years ago, but they were trying to achieve genetic purity, counter to what we are perpetuating today through scientific advances.

Science has also made it possible for people like Stephen Hawking to be valuable parts of our community! I prefer to believe that a person's 'viability' is a product of their actions and not their genetic code.


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WT21
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Feb 10, 2009 19:17 |  #21

SkipD wrote in post #7299137 (external link)
The problem is that those sources of information are confusing the heck out of new photographers. There are so many incorrect beliefs that folks apparently get from those sources that those of who do the teaching here a lot try to get the newbies to regroup and rethink the truths without all the bunk.

For example, 50mm lens is not a "normal" focal length for any other format than the 35mm film format (using the 24mm by 36mm film frame). However, many newbies do their reading and seem to be stuck on the idea that a 50mm lens has a magic perspective about it and should be the ideal lens for any format camera.

Many DSLR newbies come from using point and shoots. Point and shoot actual FL's can range quite a bit. Do you advocate that one person should be talking about an 8.3mm FL, against someone else's 4.2mm FL, even though they provide the same FOV? You'd have to teach people how to translate those FLs into degrees to talk about the FOV.

Granted, that might be better for all involved, but you are talking about redirecting an entire industry that has already developed a short hand for this in 35mm eq. More power to you if you can do it, but it strikes me as rather Sisyphean.


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SkipD
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Feb 10, 2009 19:18 |  #22

WT21 wrote in post #7299135 (external link)
Also, it is not a bad thing to have reference standards in technology.

I agree with that statement by itself. However, there are so many camera formats in the world - some old and forgotten, but many still with us - that the 35mm film format has never been and will never be the master format against which all others are measured.

Even the camera manufacturers only use the 35mm comparisons for small cameras that, for many folks, replace what the 35mm film cameras of a few years ago represented for the average amateur photographer.

Before the advent of the digital point-n-shoot cameras, most point-n-shoot cameras (other than "box" cameras which often used film cartridges) were in fact using 35mm film. I suppose the manufacturers of today's digital point-n-shoot cameras assume the buyers of them still have some connection to the old 35mm point-n-shoot cameras.

However, there is at least one generation of new photographers who probably would not even recognize a 35mm film cassette if it were shown to them in silhouette. So why do we need to stick to the 35mm reference so much today? In my opinion, we don't.


Skip Douglas
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xarqi
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Feb 10, 2009 19:25 |  #23

WT21 wrote in post #7299135 (external link)
SkipD and Wilt cannot redress it. Two people against a massive industry?

Three, at least! ;)

Get real.

Last time I checked I was - where's that label again - yeah - made in NZ!

It's misleading and not helpful to tell newbies to forget it, though explaining it is helpful.

Here we differ a little. For beginners, the crop factor issue confuses more than it elucidates, and little would be lost if they ignored all references to it. It is primarily a marketing tool used to make tyros believe that less is actually more. Sooner or later though, there is a case for explanation of the basis.

Might as well be the boy with your finger in a dike.

No comment.

Also, it is not a bad thing to have reference standards in technology. Or, could someone explain to me why it is a bad thing.

Standards are fine. Why not recorded angle of view? Feel like a crusader? One against the world, remember.




  
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mrkgoo
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Feb 10, 2009 19:33 |  #24

I agree the concept of crop factor as it's used by the industry is very confusing. Just see how many threads per week we get of people wondering if an EF-S lens focal length 'has taken into account the crop factor'. I myself wondered the very same thing when I started out.

Phigment: Perspective doesn't need to be taken into account - because that never changes with either focal length or sensor size. (whoops, here we go again!)




  
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Wilt
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Feb 10, 2009 19:42 |  #25

phigment wrote in post #7299147 (external link)
Yes, all lenses mounted on a crop body still need to be multiplied by the crop factor to get the same field of view as on a full frame. But this doesn't account for other factors such as depth of field and perspective.


Science has also made it possible for people like Stephen Hawking to be valuable parts of our community! I prefer to believe that a person's 'viability' is a product of their actions and not their genetic code.

I hardly consider Hawking to be inferior to most of us...he has a physical limitation but a far superior intellect!


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xarqi
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Feb 10, 2009 19:47 |  #26

Wilt wrote in post #7299360 (external link)
I hardly consider Hawking to be inferior to most of us...he has a physical limitation but a far superior intellect!

If I multiply my IQ my 1.6, can I do quantum cosmology too? ;)




  
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Wilt
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Feb 10, 2009 19:48 |  #27

xarqi wrote in post #7299059 (external link)
The cheetah went though a population bottle-neck where the number of individuals is estimated to have fallen to under 200. They are now so genetically similar that a skin graft from one would not be rejected by any other. All it takes is for a new bug to come along to which none have resistance as a result of underlying genetic diversity, and that will be the end of that species.

Genetic diversity is the very foundation of evolution; eliminate it and not only do you guarantee evolutionary stagnation, you sow the seeds for extinction.

But what is not adequately addressed is the 'survival of the fittest' concept, whereby the genetic diversity gives way so that genetically weak die off and only the strong survive to procreate the succeeding generations as even better than their forebears. Kind of like digital cameras...the weak quickly die off, leaving us with superior products, right?!


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Wilt
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Feb 10, 2009 19:53 |  #28

xarqi wrote in post #7299392 (external link)
If I multiply my IQ my 1.6, can I do quantum cosmology too? ;)

IQ (intelligence quotient) is like FL (focal length)...you can equate it to something similar, but never convert it via multiplication :) "Doing quantum mechanics to an Einstein is like doing fractions to a severe Downe's Syndrome person" but IQ of 180 (or whatever) is never equal to IQ of 80.


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phigment
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Feb 10, 2009 19:56 |  #29

mrkgoo wrote in post #7299302 (external link)
Phigment: Perspective doesn't need to be taken into account - because that never changes with either focal length or sensor size. (whoops, here we go again!)

Ah, you are correct. My bad.


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Quad
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Feb 10, 2009 20:00 |  #30

So how do you feel about Hasselblad material that mentions the crop factor (presumably against 6X6) when they have not only changed the format size but the aspect ratio? I know how I feel about it.

How about an Olympus lens I saw on the shelf that had the crop factor (equivalents expressed in mm) on a lens with one of those big stickers that they use on P&S's declaring the pixel count etc. but this had the crop factor in large letters followed by the real focal lengths in small letters?

When you are fighting marketers well that is a tough fight.




  
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