EF vs EF-S practical difference ?

I know this topic might have been asked several times, I have read most of them, but have not understood one point. So asking here, to get a clear idea.

I learned that EF-S lenses are designed specifically for APS-C lenses. They have lighter weight and lesser complications and glass compared to typical EF lenses. And also, they cost less in making, fine.

Some people even claimed EF-S focuses better on APS-C but I don't know about that.

But what I have noticed is, even if we mount an EF-S lens on an APS-C body, crop factor still exists. Like 10mm becomes 10*1.6 = 16mm.

(Some manuals explain that there is a smaller image circle as well, so we lose less light - does this matter when it crops? )

So my question is, what's the point of buying an EF-S lens, if the crop factor still exists?

What advantage does it have for APS-C Canon bodies?

A full-frame camera has a sensor that’s 2.5x larger than an APS-C camera. It’s possible to build smaller, lighter lenses which can focus an image onto the 2.5x smaller APS-C area.

That’s what EF-S lenses are: Lenses designed to focus onto a smaller area. This is why they are smaller and lighter, but this doesn’t make them lower quality.  Of course, they are intended for a higher volume consumer market, which is more price sensitive, so you won’t see exotic lens construction techniques such as aspherical design and fluorite coatings.  The general philosophy with Canon and Nikon is that when people buy expensive lenses, they’ll want them to work with both APS-C and full frame.

Steve Balcombe wrote:

The first part is correct - the crop factor applies to any lens you fit, whether EF, EF-S, or another brand, or even a lens fitted via an adapter. This is because focal length is a property of the glass only.

But 10 mm doesn't "become" 16 mm.

A 10 mm lens on a 1.6x crop sensor has the same field of view as a 16 mm lens on a full frame sensor. We therefore say it has an "equivalent" focal length of 16 mm, but it doesn't "become" 16 mm. It's still 10 mm.

Pardon my vocabulary here sir. Yes, I learned the same thing, it's field of view.

"Become" is a bad word typed in haste out of curiosity to know the answer.

The equivalent focal length merely provides a convenient reference point, so we can compare not only full frame and crop DSLRs, but also compact cameras.

(Some manuals explain that there is a smaller image circle as well, so we lose less light - does this matter when it crops? )

That's just confusing matters. I'd ignore it. Any lens of a given f-number will cast as much light on your sensor as any other. (Ignoring technical differences such as vignetting and transmittance which are outside the scope of a quick answer.)

But you know, some people even said, not just focal length, but f stop is considered as f*1.6 for crop sensors. That's why I was wondering if this is true. Even a video of Tony Northrup shows the same thing about f stop *1.6.

So my question is, what's the point of buying an EF-S lens, if the crop factor still exists?

For the reason you stated at the beginning - economy. Also because design trade-offs may mean an EF-S lens (or other manufacturer's equivalent such as Sigma DC lenses) can be given a larger aperture or a greater zoom range, for example.

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So finally, it is economy then. Means people who might upgrade to FF after few years, are better off buying an EF then ? if we can afford.

McArth wrote:

So finally, it is economy then. Means people who might upgrade to FF after few years, are better off buying an EF then ? if we can afford.

It’s more than that. Full-frame lenses weigh much more. And because of the field of view issues, it is far more practical to buy the EF-S lenses for wide angle. For example, Canon’s 10-22mm lens is only about $300, and and EF 11-24 (full-frame) will cost you $2,700. Tell me how hard that decision is... The 11-24 is a very special lens, because in full-frame, it’s an ultra-ultra wide angle, much wider than the 10-22 is on a crop body.

You can carry a DSLR with the 10-18, 18-55 and 55-250 EF-S lenses very comfortably. Carrying their full-frame equivalents probably doubles weight. In buying full-frame lenses, the places you’ll start are with fixed length (prime) lenses and with telephoto zooms. Lots of wildlife and sports photographers use Canon crop sensor cameras with full-frame “big white” zoom lenses, especially the 70-200 f/2.8 and the 100-400mm. The 55-250 EF-S is nice, but nothing compares to the quality of Canon’s L-series telephoto zooms. They’re in a league all their own.

McArth wrote:

I know this topic might have been asked several times, I have read most of them, but have not understood one point. So asking here, to get a clear idea.

I learned that EF-S lenses are designed specifically for APS-C lenses. They have lighter weight and lesser complications and glass compared to typical EF lenses. And also, they cost less in making, fine.

Some people even claimed EF-S focuses better on APS-C but I don't know about that.

But what I have noticed is, even if we mount an EF-S lens on an APS-C body, crop factor still exists. Like 10mm becomes 10*1.6 = 16mm.

(Some manuals explain that there is a smaller image circle as well, so we lose less light - does this matter when it crops? )

So my question is, what's the point of buying an EF-S lens, if the crop factor still exists?

What advantage does it have for APS-C Canon bodies?

The camera applies the crop factor. Focal length is focal length. An APS-C lens may not cover the “full-frame” image circle, but the lens, itself, is not performing the actual cropping, to the final aspect ratio. 10mm does not “become” 16mm. The 10mm angle-of-view is “seen” as being equivalent to the angle-of-view of a 16mm lens on a 1D/5D/6D.

To add a bit of perspective to this, Canon, until somewhat recently, produced 1D-series cameras with a an intermediate-sized APS-H sensor, with a 1.3x crop factor.

An EF-S lens may actually be useful on the larger-sensor cameras, but because EF-S lenses protrude farther into the camera, the camera’s mirror assembly, as it moves, will strike the lens. Some have modified EF-S 10-22mm lenses, enabling them to function from about 16mm, to 22mm, in 5D cameras, with no crop factor. (CAUTION: Zooming-out such modified lenses will allow the rear elements to be struck by the mirror!)

Third-party lenses, made specifically for Canon APS-C cameras, do not protrude deeply enough to be struck by the mirror assembly of “full-frame” cameras. These lenses will function on “full-frame” cameras, but the corners and edges will normally vignette heavily, especially at the shorter focal length of the zoom lenses. (All lenses vignette, to a degree, but not as heavily as seen when viewing the world through an APS-C lens on a “full-frame” camera.)

Nikon DX lenses, made for Nikon APS-C cameras, are safe to use on Nikon FX (“full-frame”) cameras, but will tend to vignette, as described above. Nikon FX cameras can be set to DX mode, which crops the image, in-camera, so this vignetting does not show.

Is there a “point” to buying EF-S lenses? Good question. You will receive a wide range of answers. In my case, I bought only one new EF-S lens, the 10-22mm, because I anticipated adding a pre-owned 5D rather soon. Notably, the EF-S 10-22mm lens compared very favorably to the EF 16-36mm L lenses of the time, so I planned to keep using it on a 7D after I bought a 5D, and this is exactly what I did, for about seven years of frequent use, until a partial separation of barrel assemblies occurred, in late 2017 or early 2018.

I think the chief advantage of EF-S lenses is that overall size and weight are reduced. The average consumer/user does not like large, heavy cameras and lenses. Another advantage is that moving the lens elements closer to the sensor, all else being equal, is ideal, from an optical engineering point of view. I do not know enough about optical engineering to take this latter part further, so will not try.

On a practical level, I have continued to use Canon APS-C cameras, to the present day, even though I bought my first pre-owned 5D in late 2011, added pre-owned 1D Mark II N cameras in late 2012 and early 2013, added a 5Ds R in 2016, and added a 5D Mark IV this year. My “on-duty” kit, when I retired from police service in early 2018, was a pair of 7D Mark II cameras, a 100/2.8L Macro IS, a 24-70/4L IS, a Macro Ring Lite II, and several Speedlites, from 580EX to 600EX-RT, mostly contained in a Pelican 1510 Case. This does not mean that I am an expert, of course, , just that APS-C cameras can be used for serious purposes.

Again, I am not an expert, and not an engineer. Some have said that I “talk like an engineer,” but, well, the math became too difficult, so I never went into engineering. I recently retired, and wonder, sometimes, whether I could get remedial training, and re-wire my brain, to better understand math, in my late fifties.

I put “full-frame” in quotation marks, because it is a relative term. Now that we have digital sensors larger than the 36mm x 24mm dimensions of the 35mm film negative, should we call them “fuller frame?”  Nikon avoids such issues by simply using the term “FX” when referring to full-36x24mm-frame size.

McArth wrote:

But you know, some people even said, not just focal length, but f stop is considered as f*1.6 for crop sensors.

It depends on what you mean by "considered as". If you want the same depth of field with FF and APS-C cameras, then yes, you need to use 1.6 times the F number on a full frame camera. FF cameras just require different settings to take the same picture. That's all they're saying.

(But it also means that APS-C sensors are slightly more limited. You probably cannot get quite as narrow a depth of field on APS-C as you can on FF. For example, you can easily get f/1.6 on FF, but you probably can't get f/1.0 on APS-C.  The converse is not true. You can get just as wide a depth of field on FF as on APS-C.)

Steve Balcombe's first reply was perfectly correct, well presented, and easily understood. I think that plus this reply are really all you need to know, although the other replies are also correct and add useful information.

Keep it simple and don't overthink it. There's a lot of confusing, misleading, and false information out there.

In addition to what's been said, the difference is actually clear in the name - S. It stands for "Short back focus" - it allows the rear element to be physically closer to the sensor than in an EF lens, because it has a smaller mirror to clear. And that, as well as the smaller image circle, is what allows lens designers a bit more freedom to produce cheaper, smaller and lighter lenses which retain reasonable quality.

you won't get UW with EF.  you won't get standard zoom with EF.

ed rader wrote:

you won't get UW with EF. you won't get standard zoom with EF.

Speaking of misinformation, Canon has an EF 11-24 fisheye lens, I believe also an 10 mm primerectilinear lens, and some EF 16-35 mm lenses. Also some EF 24-100 mm lenses.

ThrillaMozilla wrote:

ed rader wrote:

you won't get UW with EF. you won't get standard zoom with EF.

Speaking of misinformation, Canon has an EF 11-24 fisheye lens, I believe also an 10 mm primerectilinear lens, and some EF 16-35 mm lenses. Also some EF 24-100 mm lenses.

Yeah, thst's misinformation. 

The 11-24 is rectilinear. No 10mm rectilinear prime exists (shortest is 14mm). Yes, there are 16-35mm lenses, but no 24-100s (being a bit pedantic here, they're 24-105s). There IS a fisheye zoom, the 8-15.

I think the previous poster meant that no EF lens provides an ultrawide option on APS-C. Apart from the11-24, that's correct; 16-35 isn't ultrawide on APS-C, nor is 14mm, and 24-105 isn't even ultrawide on full frame. The fisheye zoom does offer a diagonal fisheye option for APS-C, but people don't generally refer to a non-rectillinear lens as an ultrawide.

So the 11-24 - it's a remarkable and wonderful lens, but it's enormous, heavy and very expensive. Yes, you could use it as an ultrawide on APS-C, but it's a perfect example of the difference between EF and EF-S (and even more so, EF-M). There are 2 EF-S lenses that are a fraction of the size, weight and cost and that are actually a fraction wider, the 10-18 and 10-22 - they don't have the same optical quality, but are not bad at all and are much more suited to APS-C cameras in terms of size, weight and budget.

So yeah, Ed could have been clearer, and is technically incorrect about the 11-24, but that less actually is the perfect example of the difference anyway.

Rock and Rollei wrote:

ThrillaMozilla wrote:

ed rader wrote:

you won't get UW with EF. you won't get standard zoom with EF.

Speaking of misinformation, Canon has an EF 11-24 fisheye lens, I believe also an 10 mm primerectilinear lens, and some EF 16-35 mm lenses. Also some EF 24-100 mm lenses.

Yeah, thst's misinformation.

The 11-24 is rectilinear.

DPR lists it as both rectilinear and fisheye.  I don't see where to report the error.

No 10mm rectilinear prime exists (shortest is 14mm).

There's a patent on a 10.  I think I remember seeing a review--maybe not.

Yes, there are 16-35mm lenses, but no 24-100s (being a bit pedantic here, they're 24-105s). There IS a fisheye zoom, the 8-15.

Correct.

I think the previous poster meant that no EF lens provides an ultrawide option on APS-C.

Probably so.  That makes sense.

So this is a topic it's hard to get into without strong opinion. Most of the technical issues have been covered pretty well. I'll mention a practical situation for me that marks why sometimes I'll go for the EF-S lens over the EF

It almost always comes down to *Wide Angle*

Up until recently I did not have any IS lens that was also fast for indoor shoting. I have an old Sigma zoom that was fixed f2.8 but it never got great results and had no IS, so often my stabilized Tamron F3.5 18-270 could get a better picture even though it's a slower lens and lower image quality.

That Tamron has been my do-it-all-okay lens for a long time. It's been down many a backpacking trail and probably will be for a long time to come. Why? Because it's lightweight for APS-C sensors. When every gram matters like a multi-day backpacking trip that means a great deal.

What I wanted was something that works well with no or minimum flash for indoors shots and didn't lose the wide angle end of the Tamron.  I could lose the extreme telephoto end as that's not really as big a concern to me indoors.  In the EF lenses that doesn't really exist for APS-C gear mostly limited by the wide angle requirement.  Most EF zooms are going to end at 24mm as the wide end which is pretty far from a wide-angle view on APS-C.

I ended up getting the Canon 17-55 f2.8. It covers that range that I wanted at the sacrifice of a little more telephoto than I wanted to give up but with excellent image quality at an affordable price tag.

but I plan to eventually acquire the 70-200L f2.8 IS to cover that telephoto need and maybe dabble with a bit of outdoor wildlife with a 1.4X extender.

I don't see myself ever shelling over the cash for a full-frame body. APS-C has been good for my needs and lets me carry smaller lighter lenses. I would be highly unlikely to go backpacking with the 17-55/70-200 combo because of weight. Here again, that lightweight Tamron 18-270 makes all kinds of sense for me out in the bush.

If he didn’t figure this out two years ago, it’s hopeless.