What is the difference between EF and EF-S lenses and what is STM?

[ScottyP · Accepted solution]

Hi.

EF lenses work on both types of Canon DSLR; full frame and crop sensor cameras.  Some are affordable and some are very expensive.

EF-s lenses only work on crop sensor cameras, and are consumer grade, affordable lenses.  

STM is just a quieter focus motor in a lens. People who do a lot of video like that, because you are less likely to hear the sound of the lens focusing recorded in your videos.  Ultrasonic (USM) focus is the other good focus motor, and it is pretty quiet too, and it is faster for sports, etc...  I would not worry much (or at all) about getting STM over USM unless you are shooting a lot of video and you are pretty particular about it.

Full Frame cameras.  Full frame cameras have a sensor equivalent to the old 35mm film size. The lenses will all give you the field of view stated on the lens, so 50mm will really be 50mm, 35mm is 35, 200 is 200, etc.  Full frame cameras include mostly pro and advanced enthusiast models such as 1Dx, 5D3, but there is also the more affordable 6D (which I use).

Crop cameras.  Crop sensor cameras have a smaller sensor.  The sensor is smaller than the image cast upon it, so the image splashes out around of the edges of the sensor.  This means the image is basically cropped down and you lose the edges, which is like zooming in on every shot, once the image is displayed at full size. The "zoom factor" is 1.6x the normal focal length of the lens, so a 100mm lens will give you an image that appears to be 160mm, a 200mm lens will give a field of view like a 320 lens, etc...  Crop cameras include the entry level cameras like Rebel T5, and the next step up like Rebel T5i, T6i, etc., and then the next step up, the 70D, and finally the high-end 7DII.

L lenses.  EF lenses are further divided into regular lenses and "L" lenses. The "L" lenses are higher quality both in optics and in construction, and some of them are to some degree weather resistant (not waterproof!). And they are much more expensive.  They have red rings on the ends.

[ScottyP · Accepted solution]

Hi.

EF lenses work on both types of Canon DSLR; full frame and crop sensor cameras.  Some are affordable and some are very expensive.

EF-s lenses only work on crop sensor cameras, and are consumer grade, affordable lenses.  

STM is just a quieter focus motor in a lens. People who do a lot of video like that, because you are less likely to hear the sound of the lens focusing recorded in your videos.  Ultrasonic (USM) focus is the other good focus motor, and it is pretty quiet too, and it is faster for sports, etc...  I would not worry much (or at all) about getting STM over USM unless you are shooting a lot of video and you are pretty particular about it.

Full Frame cameras.  Full frame cameras have a sensor equivalent to the old 35mm film size. The lenses will all give you the field of view stated on the lens, so 50mm will really be 50mm, 35mm is 35, 200 is 200, etc.  Full frame cameras include mostly pro and advanced enthusiast models such as 1Dx, 5D3, but there is also the more affordable 6D (which I use).

Crop cameras.  Crop sensor cameras have a smaller sensor.  The sensor is smaller than the image cast upon it, so the image splashes out around of the edges of the sensor.  This means the image is basically cropped down and you lose the edges, which is like zooming in on every shot, once the image is displayed at full size. The "zoom factor" is 1.6x the normal focal length of the lens, so a 100mm lens will give you an image that appears to be 160mm, a 200mm lens will give a field of view like a 320 lens, etc...  Crop cameras include the entry level cameras like Rebel T5, and the next step up like Rebel T5i, T6i, etc., and then the next step up, the 70D, and finally the high-end 7DII.

L lenses.  EF lenses are further divided into regular lenses and "L" lenses. The "L" lenses are higher quality both in optics and in construction, and some of them are to some degree weather resistant (not waterproof!). And they are much more expensive.  They have red rings on the ends.

[TitanSword]

Thank you Scott, Tim and others that have posted a response to my question. The responses are very helpful and will help me make a decision as to what my next lens purchase is. I printed yours, Tim and Scott, thank you.

I used to shoot film back in the 80's & 90's and put my camera (a Canon 10S w/a Canon 28-105 lens) down and have not shot anything, on a regular basis, in over 15-20 years. If you remember the10S is an EOS body, I believe after the 600 series and had a bar code reader to set up the camera, according to a book of sample photos, displaying barcode   Well I have been bit by the bug, once again, and am starting to put together a digital kit. My first purchase was a lens I have been wanting for a really long time, a Canon EF, 70-200, f2.8, IS II, of which Canon is very proud of. I have shot with the first in the series and have wanted one ever since. Now for the body, I am looking at the Canon 7D Mark II and the 70 D, but leaning towards the 7D Mark II. 

Tim, what do you think of the, Canon 60Da?  Do you use it to shoot Astrology?

[ebiggs1]

" Do you use it to shoot Astrology?"

I doubt it but maybe.  No, just kidding, he uses it for astronomy.

Anyway another point since you said you bought a fantasticly wonderfull, my very favorite, lens the EF 70-200mm f2.8 L II.

EF-S lens are not in the same class as this lens.  There are no "L" lenses in the EF-S line. I maintain it is best to keep you outfit equal in quality.  It just works better that way.

You can't be thinking 70D and 7D Mk II in the same sentence?  Go for the 7D Mk II.  IMHO, of course.

[ScottyP]

The 70-200 f2.8 L Mk.2 is a truly lovely lens. I am still blown away every time I look at a batch I shot with it. It was love of this lens that made me go full frame. (Well, that and the better IQ in low light at hih ISO). The 70-200 range was often a little too long for everyday shooting when mounted on my old crop camera, being cropped in by 1.6x on every shot. It worked great on sports, etc., but for much other shooting, 70mm x 1.6 = 112mm was just too long., and there were many occasions when it simply meant I could not use it. Now on full frame, 70-200 really is 70-200 and I use the lens a lot more.

What will you be shooting?
Outdoor daylight shots or indoors/nighttime?
Fast action or slow/stationary things?
Smashing the camera against rocks in the rain and abusing it or mostly average use?

It is possible you may want to go full frame depending on some of the answers above. And even if crop is right for you, you may not get much benefit from the 7d2, all depending on what /where and when you shoot.

[TCampbell]

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@TitanSword wrote:

Tim, what do you think of the, Canon 60Da?  Do you use it to shoot Astrology?

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There's a joke that says if you want to make an astronomer angry... just call him an astrologer.

I tell people at the planetarium shows that if they call me an astrologer, I'll respond by giving them bad relationship advice, bad career advice, bad financial advice, etc. etc.  😉

On the serious side... I love the 60Da, but it helps to understand what sets it apart.

Prior to my 60Da and even my 5D III, I had a a 5D II (actually I still have that camera).  I was at a friends house using his observatory and he had shown me an image that another club member had taken only the previous evening using the same telescope -- but with a 60Da.   Since I had all the info and access to the same scope in identical conditions, I thought why not take some exposures of the same image and see what we get using a 5D II (KNOWING that a 5D II body's ISO sensitivity is significantly better than a 60D.)

We took the same image at the same ISO for the same duration and I got... practically NOTHING showing up.  Surprised by this, I doubled the exposure and tried  again.  This time... still very little.  I could see the object, but it was very weak compared to what the 60Da captured (in half the time).  So... I doubled the exposure again (now I'm running an exposure which is 4x as long).  Now I'm finally starting to see the object, but have to confess that the image out of the 60Da looks better.  

The following day I did research on the 60Da and within a week I ordered one of my own.

Here's what's going on...

When people talk about how great the colors look on various cameras, you have to remember that there's no such thing as "color" in the Universe.  This is an imagination of the human brain.  The visible portion of the eletromagnetic spectrum runs from roughly 400nm on the short end (blue) to 700nm on the long end (red) with green being half-way in between (about 450nm).  But it turns out your eyes are not actually equally sensitive to the colors of the visible spectrum.  Human eyes are highly sensitive to green... but not particularly sensitive to blues or reds.   

A camera sensor (without engineers doing anything special) would normally have somewhat equal response to all these wavelengths.  This creates a problem because the job of the camera isn't to image what's REALLY there... it's supposed to image what a HUMAN eye would see.  To compensate, the sensor has twice as many photo-sites on the sensor which are sensitive to "green" as compared to the number sensitive to red or blue.  And as if that isn't enough... it also using an IR block filter which gently ramps the amount of red light being blocked started at only 500nm... and increasing steadily until it reaches 700nm (at which point it pretty much cuts off all light.)

Here's where this ties into astrophotography:  The most common element in the universe is hydrogen -- being about 70% of all normal matter in the universe.  Hydrogen atoms emit energy photons following something called the "Balmer" series where they pump out phons that have wavelengths in a fire-engine red color (656nm), followed by a sky-blue color, followed by a deeper blue, and so on.  You can see it here:   http://en.wikipedia.org/wiki/Balmer_series

When we capture images of deep-space objects (particularly emission nebula) they are PROBABLY most strongly glowing in the Hydrogen alpha wavelength... that fire-engine red color that has a wavelength of 656nm.  

But the human eye isn't supposed to be very sensitive to that wavelength, so normal cameras are blocking about 80% of the light at that particular frequency.  This means when you take a photograph of a nebula rich in Hydrogen alpha (which is most of them) you end up having to take a MUCH longer exposure to compensate for the fact that the camera is deliberately working to block the very wavelength of light that you want to collect.

The 60Da still has an IR cut filter... but rather than starting to gently block reds at 500nm and increasing the block until it finally reaches full cut-off at 700nm, the filter is designed to block almost nothing until it reaches 700nm and then do a very agressive hard-cutoff (rather than gently sloping increase of a normal filter.)

That's why my friend's 60Da could capture a better looking image in less than 1/4 of the time it took my 5D II.

If you use the 60Da to take "normal" terrestrial photos, you'll notice everything looks quite "warm".  You can back this off via white balance (of course you'd do this for every shot you take).  As such, the 60Da isn't well-suited for normal terrestrial photography, but it's fantastic for astro-imaging.

[RobertTheFat]

TCampbell wrote:

If you use the 60Da to take "normal" terrestrial photos, you'll notice everything looks quite "warm".  You can back this off via white balance (of course you'd do this for every shot you take).  As such, the 60Da isn't well-suited for normal terrestrial photography, but it's fantastic for astro-imaging.

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Wandering far OT (and admitting it), ...

I've always wondered why physicists and astronomers (and especially photographers) persist in referring to a red bias in an image as "warm". We all know that higher temperatures are correlated with bluer radiation and that, if anything, redder colors are generally associated with cooler objects. I suppose that the anomoly is entirely linguistic, deriving from the fact that fire is red and the sky and large bodies of water are blue. In truth, I have a great affection for linguistics, but I still confess to finding the usage a bit jarring. 

[TCampbell]

Yes - for stars, the bluer the light, the hotter the star and the redder the light the cooler the color.   For emission nebulae, the colors tell us which elements are present in the gases (and read like a "bar code").

And yet for photography, we still refer to red as being "warm" and blue as being "cold".

[RobertTheFat]

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@TCampbellwrote:

Yes - for stars, the bluer the light, the hotter the star and the redder the light the cooler the color.   For emission nebulae, the colors tell us which elements are present in the gases (and read like a "bar code").

And yet for photography, we still refer to red as being "warm" and blue as being "cold".

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But when we talk about color temperature, we get it right: bluer = a higher temperature.

[ScottyP]

Clearly you guys don't keep up with cartoons. If a character freezes, he turns blue, and indeed, ice is drawn as blue, ergo blue = cold. The entire Disney merchandising Goliath that is the Frozen movie observes this coloring convention for the youngsters. Elisa's ice dress is blue. Cartoon fires have a warm orange glow.

Seriously, though, no one on the street, not even most photographers or even scientists would look at a blue color palette at the paint counter and think "warm colors".