EF-S lens crop factor

[linda_pullman]

When you attach any EF-S lens to a 10/20D body, do you calculate crop

factor? For example, when you have 10-22mm EF-S lens on your camera,

is 10-22mm a real focal length range (like on 35mm body)? Or is it 16-

35.2mm?

 

Thanks - Linda

[juan_ignacio_pe_a]

Yes you have to calculate de crop factor. The 10-22, is a 16-35.

[photobyalan.com]

10-22mm is the actual range of focal lengths. The field of view of the lens on an APS-size camera will be approximately equivalent to that of a 16-35 on a 35mm camera.

 

I, for one, wish people would stop thinking about "factors" (it's not really a crop, anyway, any more than placing a 4x5" sheet of film behind a lens that has enough coverage to allow for movements is a "crop") and get to know your cameras. The photography world no longer revolves around 35mm film.

 

If you're using an APS-sized DLSR, 35mm is a "normal" lens.

 

20mm is wide.

 

10mm is ultra wide.

 

50mm is a short portrait lens.

 

85mm is a long portrait lens.

 

Anything over 100mm is a long lens.

 

Anything over 200mm is a very long lens.

 

 

From that short list, anyone can figure out what they need as far as focal lengths are concerned.

[erik_eilers]

LIke alan said,

The crop factor is just a crop. There is no extra magnification just because the sensor is smaller than film. So a 10-22 has the photo footprint of a 16-35, but the magnification of a 10-22. Meaning if you took an image of a person at the same distance with a 10-22 set at say 15mm, with film then with digital at the same settings, and compared the two images at the same scale, the people will be the same size, but the film will have a larger footprint because of size of the film.

Alan, chill out! 35mm film has been around a lot longer than digital, and people are going to be comparing it to that for years to come.

 

Hope this helps Linda

Erik

[bobatkins]

<em>The photography world no longer revolves around 35mm film</em>

<p>

No, but it still revolves around the 24x36mm format. It's the "gold standard" to which everything else is compared. All digicams, for example, use the "35mm equivalent" focal lengths when talking to consumers.

<p>

[jim_larson1]

<i>No, but it still revolves around the 24x36mm format. It's the "gold standard" to which everything else is compared. All digicams, for example, use the "35mm equivalent" focal lengths when talking to consumers. </i>

<p>

Yeah, I agree with Bob's statement. . .when talking to people who are not as well versed in the nuances of DOF and crops, the 35mm equivilent is very appropriate for a reference.

<p>

But in reality a 35mm lens is a 35mm lens no matter what body it is mounted on. Depth of field is a constant for a given aperture. What changes is the field of view. This is why P&S cameras can't produce a decent portrait: the lenses are all like 7-21mm and as a result have horribly huge depth-of-field combined with a 2.8 or larger aperture.

<p>

The classic portrait lenses such as the 85/1.8 and 100/2 are both longer and have larger apertures. . .which results in really shallow DOF for portraits.

<p>

So now that I have shot more frames with my dSLR than I ever shot with my film SLR, I actually tend to think in terms of the true lens focal lengths.

[bill_muth]

Referring to focal lengths/FOVs in "35mm equivalent" may not be totally accurate, but given the number of photographers who've used 35mm cameras and/or been exposed to "35mm equivalents" and considering the wide range of sensor sizes, it's the best system there is. Just in the DSLR world, there are cameras with crop factors of 1, 1.3, 1.37, 1.5 , 1.6, 1.7 and 2.0 (not including some discontinued models like the Kodak DCS 315 with its 2.6 factor.)

[jon_austin]

Linda: You can't attach any EF-S lens to a 10 body, unless you permanently modify the lens first.

 

Alan : Yes, it really is a crop. And a further example of the "world revolving around the 36x24mm standard" is the fact that the specifications for most zoom digicams state the range of their zoom lenses in both actual and 35mm equivalents.

[photobyalan.com]

Jon,

 

So, according to your logic, when you don't use the entire image circle of the lens, it's a "crop". Try telling that to anyone who shoots large format or who uses a T&S lens on a 35mm camera.

 

Calling it a crop is just plain wrong.

[chrisjb]

Hi Linda. I`m in agreement with Bob & Jim as a lot of lenses are still produced for 35mm cameras and now used on Dslr. In years gone by the standard lens for correct perspective was a 50mm the easiest way to calculate this was draw a line from corner to corner of a 24 x 36 neg and it measures 50mm, If you measure a Aps c sensor its appros 35mm hense by using a 50mm lens it is in effect an equivalent in perspective a 85mm lense (x 1.6)

 

I think as 35mm phases out this 1.6 factor will not be added into the equation and simply as more atart taking pics 50mm and 85mm will be poetrait lenes 12~17 normal wide angle. but we still need some bench mark to compare while using the same lenses for 2 systems

 

hope it helps

[markci]

The problem with your theory, Alan, is that there are many sensors of different sizes, some even by the same manufacturer (ie Canon). And that's not even considering point & shoot digicams and their micro sensors of about five different sizes. Your little table therefore has very limited utility.

 

The "crop factor" (and no, nobody particular cares if you don't like the term) is extremely useful in that it converts actual focal lengths, which are no longer particularly useful for determining coverage angle, to something that is, in a simple and uniform way. Something that's familiar to most people. It's worth the minor, meaningless imprecision of the terminology, and almost worth putting up with the pedentry of people on the Internet complaining about it.

 

It's not particular to digital, either. A lot of photographers think "factor of two" in relating medium format lenses to 35mm and "factor of four" for 4x5.

[markci]

Sorry..."pedantry."

[david_kieltyka]

Given that roughly 98% of all D-SLRs sold to date do not use the 35mm format, and given that this percentage is likely to hold true for a good while, to me it makes sense to understand focal lengths in relation to the formats people are actually using rather than one they're not.

 

But I think what Linda's question gets at is different than the

discussion it has provoked. Terms like "crop factor" and "equivalent focal length" have left lots of folks confused as to what exactly a focal length is. Is it a description of a particular amount of coverage (wide, normal, long) or is it a hardwired optical property of a lens? The answer is the latter. Focal length by itself tells you nothing about coverage.

 

Canon has labeled the 10-22mm lens as 10-22mm because that's the real focal length range (give or take a mm or two at each end). The lens will give you narrower coverage on a Canon 20D than it would if you were able to mount it on a 1Ds. But you can't do that so the whole "crop factor" issue is non-existent. The lens only works on APS-C format cameras, where 10mm is ultra-wide and 22mm moderately wide.

 

-Dave-

[bobatkins]

It doesn't matter squat what lenses "should" be called whether "crop factors" and "multipliers" are accurate descriptions. That's the way the marketing world talks about stuff and that's what people understand.

 

Tell the average digicam owner his camera has a 7 to 21mm zoom and he'll look stunned. Tell him it's a 65 degree to 25 degree field of view zoom and he'll look even more stunned. Tell him it's a 28-70 zoom and he'll be happy.

[photobyalan.com]

Bob,

I couldn't disagree with you more on your last point.

The average P&S digicam owner only cares whether he or she has a "3x" or a "12x" zoom (referring, of course, to the ratio of shortest to longest focal length of the lens), and cares nothing about the actual focal length of the lens and even less about trying to convert that to some relationship with a format they're never going to use again. That's how the lenses are marketed and that's how the general public thinks of them. Go ahead, ask some of your friends/family members who are not "serious" photographers what lens they have on their digicam. Chances are you'll either get "I dunno" or a number with an X behind it. <p>

 

Mark Ci: The problem with <i>your</i> theory is that you didn't bother to read my previous posting thouroughly before attacking me. I clearly stated that the basis of my "little table", as you call it, is a camera with an APS-sized sensor. Considering the subject of the original post is the 10D/20D, I think the "little table" is appropriate and has plenty of utility in this thread. So, next time you're going to call someone a name, however obliquely, please get your facts straight before you do it.

[jim_larson1]

<i>The average P&S digicam owner only cares whether he or she has a "3x" or a "12x" zoom </i>

<p>

Good point.<p> But those who are ONE STEP more advanced will want the 35mm equivilent. Heck I use P&S digicams and I wouldn't have a clue how to buy without the 35mm equivilent.

[kiestphoto]

Until the digicams list the sensor dimensions right on the box, and on the little card that

BestBuy/Costco has underneath the demo model and right on the camera, we all need

35mm equivalents. I use the equivalent and the actual to compare sensor size between

cameras. I think the lack of understanding by consumers of the concept / advantages of

different sensor sizes is more important to fix first.