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Canon EF 50mm f/1.4 USM
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May 31, 2017 12:23:35   #
mdougc Loc: Sarver, PA
 
I have the Canon EF 50mm f/1.4 USM lens, and use it with my Canon 70D.
I have several other lenses, but this is reserved for portraits and miscellaneous detail work.
After many years of amateur photography, I am trying to understand lens specifications at a deeper level.
Questions:
1. This is listed as a "Prime" lens. What does that really mean? How does that compare to the Canon "L" series lenses?
2. In a review of this lens, it implies that this is a full-frame lens and presents a 80mm field-of-view on an APS-C camera.
But it appears to act like a 50mm lens on my Canon 70D. I'm confused. Is the review incorrect? Or am I reading it wrong?
See the review at:
https://www.dpreview.com/reviews/canon-50-1p4-c16

Thank you for your help.

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May 31, 2017 12:46:48   #
SS319
 
A prime is a single focal length lens - as opposed to a telephoto or varifocal lens

The lens is designed to focus on a flat field covering a circle about 43-45 mm in diameter ( the diagonal of a 24 X 36 mm sensor)
Your sensor is only about 27 mm diameter. The image you collect on your sensor is the center 60% of the total image, and that is the same aspect and the same image as you would get with a 80 mm length on a full frame camera.

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May 31, 2017 13:16:12   #
jeep_daddy Loc: Prescott AZ
 
Prime means it's one focal length as opposed to a zoom lens that can go from one focal length to another by zooming.
The field of view difference between a full frame sensor and a crop sensor is what the article is talking about. Putting a 50mm lens on a crop sensor body gives the appearance of about 85mm compared to 50mm that would be realized on a full frame sensor body or a 35mm film body. Your lens is still 50mm no matter what body you've attached it to, but there would be a difference in the appearance of each image if you compare them taken on a crop body and ff body.

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May 31, 2017 13:25:09   #
SharpShooter Loc: NorCal
 
SS319 wrote:
A prime is a single focal length lens - "as opposed to a telephoto" .


????????? LoL
SS

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May 31, 2017 13:45:54   #
mwsilvers Loc: Central New Jersey
 
SS319 wrote:
A prime is a single focal length lens - as opposed to a telephoto or varifocal lens

The lens is designed to focus on a flat field covering a circle about 43-45 mm in diameter ( the diagonal of a 24 X 36 mm sensor)
Your sensor is only about 27 mm diameter. The image you collect on your sensor is the center 60% of the total image, and that is the same aspect and the same image as you would get with a 80 mm length on a full frame camera.

I assume you intended to write telephoto zoom rather than just telephoto since a telephoto lens can also be a prime lens.

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May 31, 2017 16:27:57   #
mdougc Loc: Sarver, PA
 
Thank you, but here is my confusion.
I put my camera on a tripod and aimed at a test subject with a well-defined area - a book cover.
1. First picture was shot with a Canon EF-S 18-55mm lens, set at 50mm.
2. Second picture with the Canon EF 50mm.

I get the same picture.
The way I interpret your answer, I should zoom the first picture to 80mm in order to match the shots.

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May 31, 2017 17:07:12   #
blackest Loc: Ireland
 
mdougc wrote:
Thank you, but here is my confusion.
I put my camera on a tripod and aimed at a test subject with a well-defined area - a book cover.
1. First picture was shot with a Canon EF-S 18-55mm lens, set at 50mm.
2. Second picture with the Canon EF 50mm.

I get the same picture.
The way I interpret your answer, I should zoom the first picture to 80mm in order to match the shots.


no its simpler than that

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take the above diagram the smilie getting photographed the light goes into the lens and is upside down on the sensor on the back. The pool of light through the EF-S lens is just bigger than the sensor. with the EF lens the V is wider and creates a bigger pool of light which covers the sensor and a lot of the back wall as well (designed for a 36 by 24 frame sensor) while the efs was designed for 24 by 16.

So more light makes it through the lens but it's wasted as the extra misses the sensor. if your sensor was 36 by 24 you would see more around your image with the ef lens. With the efs lens because of its smaller diameter lens elements would still show the central area but the outside edges would be black.

So your 18-55mm lens set at a focal length of 50mm shows exactly the same as the EF 50mm on your camera.

because a full frame sensor is bigger it shows more of the outside world than the smaller sensor (its using that wasted light). getting a wider field of view.

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May 31, 2017 18:54:34   #
mwsilvers Loc: Central New Jersey
 
mdougc wrote:
Thank you, but here is my confusion.
I put my camera on a tripod and aimed at a test subject with a well-defined area - a book cover.
1. First picture was shot with a Canon EF-S 18-55mm lens, set at 50mm.
2. Second picture with the Canon EF 50mm.

I get the same picture.
The way I interpret your answer, I should zoom the first picture to 80mm in order to match the shots.


50mm is 50mm. It doesn't matter if you're​ using a FF lens or a crop lens. On a crop Canon body both lens will give you an equivalent angle of view similar to 80mm on a FF body. The apparent change in focal length on a crop body has nothing to do with the lens. It's the smaller sensor on a crop camera that gives the impression of the longer focal length.

The difference between FF lenses and crop frame lenses is that FF lenses are designed to match the larger FF sensors and Crop lenses are designed to work with smaller sensors. When you use a FF lens on a crop frame body, you are actually only using the center portion of the lens with your smaller sensor. But this difference does not affect the focal length in any way.

And to answer your original question, the review is correct but you're misinterpreting it.

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Jun 1, 2017 00:20:36   #
jeep_daddy Loc: Prescott AZ
 
mdougc wrote:
Thank you, but here is my confusion.
I put my camera on a tripod and aimed at a test subject with a well-defined area - a book cover.
1. First picture was shot with a Canon EF-S 18-55mm lens, set at 50mm.
2. Second picture with the Canon EF 50mm.

I get the same picture.
The way I interpret your answer, I should zoom the first picture to 80mm in order to match the shots.


50mm is 50mm no matter what. Using a body that has a crop sensor and 50mm prime and or a 18-55 set to 50mm will be the same. But, if you took on pick with the crop sensor body and the 50mm prime and a picture with the same 50mm prime on a ff sensor body, the pic will be different.

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Jun 1, 2017 08:42:27   #
Bloke Loc: Waynesboro, Pennsylvania
 
mdougc wrote:
Thank you, but here is my confusion.
I put my camera on a tripod and aimed at a test subject with a well-defined area - a book cover.
1. First picture was shot with a Canon EF-S 18-55mm lens, set at 50mm.
2. Second picture with the Canon EF 50mm.

I get the same picture.
The way I interpret your answer, I should zoom the first picture to 80mm in order to match the shots.


There are quite a few confusing answers out there... The simple fact is, on your camera, *any* lens at 50mm will give you the same view. It happens to be that which a full-frame camera would get with an 80mm lens, but that is beside the point. The crop factor is applied to all lenses used on that camera. To see the difference, you would have to put the lens on a full-frame camera...

Ok, Jeep-daddy beat me to it. What he said...

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Jun 1, 2017 09:14:27   #
philo Loc: philo, ca
 
L means lots of money. They denote Canon best lens.

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Jun 1, 2017 09:53:04   #
mwsilvers Loc: Central New Jersey
 
philo wrote:
L means lots of money. They denote Canon best lens.

And they are Canon's professional lens line, and none of them are designed specifically for crop sensor bodies.

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Jun 1, 2017 09:57:03   #
philo Loc: philo, ca
 
mwsilvers wrote:
And they are Canon's professional lens line, and none of them are designed specifically for crop sensor bodies.

true but they can be used on crop sensor body. However a crop sensor lens cannot be used on a ff body.

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Jun 1, 2017 10:59:54   #
mwsilvers Loc: Central New Jersey
 
philo wrote:
true but they can be used on crop sensor body. However a crop sensor lens cannot be used on a ff body.


Yep.

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Jun 1, 2017 13:17:27   #
amfoto1 Loc: San Jose, Calif. USA
 
mdougc wrote:
I have the Canon EF 50mm f/1.4 USM lens, and use it with my Canon 70D.
I have several other lenses, but this is reserved for portraits and miscellaneous detail work.
After many years of amateur photography, I am trying to understand lens specifications at a deeper level.
Questions:
1. This is listed as a "Prime" lens. What does that really mean? How does that compare to the Canon "L" series lenses?
2. In a review of this lens, it implies that this is a full-frame lens and presents a 80mm field-of-view on an APS-C camera.
But it appears to act like a 50mm lens on my Canon 70D. I'm confused. Is the review incorrect? Or am I reading it wrong?
See the review at:
https://www.dpreview.com/reviews/canon-50-1p4-c16

Thank you for your help.
I have the Canon EF 50mm f/1.4 USM lens, and use i... (show quote)


First, a "prime" lens is a single focal length lens... as opposed to a ZOOM (not necessarily as opposed to a "telephoto or varifocal"... a "telephoto" can be a prime OR a zoom... and a "varifocal" is one TYPE of zoom... so a previous response is wrong. Twice.)

The "EF" designation simply means that the 50mm produces a large enough image circle to fully cover the larger sensor of a full frame digital or the 24x36mm image area of a 35mm film camera. This allows it to be used on either Canon full frame or "crop sensor" DSLRs such as your 70D (as opposed to "EF-S" lenses, which are designed to be more compact and produce a smaller image circle, so are ONLY usable on APS-C crop sensor cameras, such as yours.)

50mm is 50mm... regardless of what size sensor camera it's used upon. HOWEVER, how 50mm BEHAVES changes, depending upon the sensor format. On your APS-C camera with a sensor that's approx. 15x22mm a 50mm lens "acts as" a short telephoto... great for portraiture, among other things:


On full frame/film 50mm behaves as a "standard" or "normal" lens... neither telephoto nor wide angle. On your camera with it's smaller senosr, it acts as a short telepoto. Due to your camera's smaller sensor size, if you wanted a lens that renders a "standard/normal" angle of view, you would need a "31.5mm" focal length (which doesn't exist... but 28mm, 30mm and 35mm are all pretty close and do exist). In comparison, on a bigger medium format (45x60, 60x60mm, 60x70mm and more) or large format camera (100x125mm and larger image area), that same 50mm focal length would act as a wide or ultra wide angle lens. Or, on a camera using a smaller sensor than yours, such as a so-called 1" sensor (which Canon uses in some of their G series), the same 50mm focal length would act as a moderate to long telephoto. I say "theoretically" only because the 50mm lens would be designed differently to adequately cover larger formats or might be reduced in size for smaller formats. But it's still 50mm... focal length doesn't change with sensor/film format. It just "acts" differently.

This is the 50mm f/1.4 acting as a "normal" lens on a full frame camera:


Compare the above image to a shot made with wide angle EF 20mm f/2.8 lens on the same camera, shooting the same subject from the same location (cropped a little top and bottom, to be more "panoramic"):


The EF 50mm f/1.4 also enjoys a large aperture... allowing in up to 2/3-stop more light than the cheaper EF 50mm f/1.8 STM lens. Canon also offers the more premium and 2/3-stop "faster" EF 50mm f/1.2L. A larger aperture not only allows more light in, making the lens more useful in low light conditions.. it also can make for shallower depth-of-field effects... such as stronger background blur that can be useful for candid portraiture, among other things:


The EF 50mm f/1.4 USM is one of the oldest design Canon lenses in continuous production. It was introduced in 1993. While it's still a very good lens, it's a little surprising that Canon hasn't updated the EF 50mm f/1.4.

The 50/1.4 tends to be a wee bit soft wide open. Mine is pretty darned good and usable at f/1.4, but I still usually try to stop it down to at least f/2 for optimal image sharpness.

Other nuances include that the 50/1.4 isn't a "true" USM lens. While it has all the speed of Canon's Ultrasonic autofocus drive, this particular lens uses a hybrid form of it. Hundreds of thousands of them in use over 24 years are fine, but some have shown that problems can occur with the AF, especially if it's handled carelessly. A hard bump on the manual focus ring or the inner/front barrel can damage the AF mechanism. The solution is pretty simple: The matched lens hood made for the 50/1.4 does a good job protecting the front of the lens while shooting... and reversed for storage the hood covers the focus ring, protecting that while the lens is stowed in a bag or pocket. I've also heard some reports that frequently overriding AF manually (which is supposed to be possible with USM lenses) can cause extra wear and tear and earlier failure of AF with this lens. OTOH, I've been using mine for 15 years and it was bought used...and it still works fine. But I've always used and stored it with the hood and rarely have reason to override AF manually when shooting with it.

Another thing, you may hear or read the EF 50mm f/ 1.4 being called Canon's "Reference lens". This means it was supposed to set the standard for color rendition and some other image quality factors. 50mm "normal" lenses are among the oldest and most thoroughly developed type of lens for 35mm film cameras... some designs dating back to the 1930s. At one time, many manufacturers referred to their premium version, normal lens this way... as the "reference" upon which all the other lenses they offered in their systems were judged and designed to emulate as closely as possible. You don't hear or see reference lenses talked about a lot, any more. Maybe that's because most caemras are sold with some sort of "walkaround", general purpose zoom these days.... while years ago most 35mm film SLRs and rangefinder cameras were sold with a 50mm or something very close to it.

Sooner or later, I'm sure Canon will update the venerable EF 50mm f/1.4 USM. I ain't holding my breath.. But hopefully it will see optical tweaks to be a bit sharper fully wide open... and will get a curved, 9-blade aperture for even nicer background blur and better "sun stars"... and be fitted with a less vulnerable "true USM" focus drive system (maybe their new "Nano USM")... and maybe even have IS added (as Canon has done with updates of their EF 24/2.8, EF 28/2.8 and EF 35/2 lenses).

Hope this helps!

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