topic Re: EF-S v EF Lens - Crop Factor (Image Conversion Factor) in EF & RF Lenses

EF-S v EF Lens - Crop Factor (Image Conversion Factor)

jrjsmith — Fri, 02 Oct 2015 17:56:33 GMT

Good evening,

Please excuse me if this is a dumb question.

If I use an EF-S lens on a camera with an APS-C sensor, does the sensor capture all that I see in the viewfinder i,e, with a ratio of 1:1?

Put another way; do EF-S lenses overcome the Image Conversion Factor or Crop Factor that hapens with EF lenses on cameras with an APS-C sensor?

The Crop Factor means that what you see through the viewfinder is more than actually gets captured by the sensor by a ratio of 1:1.6.

I understand that the rear of the EF-S lens is closer to the mirror and, therefore the sensor, than the rear of the EF lens, which leads me to think that the image seen through the viewfinder with an EF-S lens is closer to that which will appear on the sensor than that of an EF lens.

Many thanks for any response that confirms or refutes my supposition, preferably with an explanation in simple terms.

Joe.

Re: EF-S v EF Lens - Crop Factor (Image Conversion Factor)

RobertTheFat — Fri, 02 Oct 2015 19:57:54 GMT

You're overthinking it. Just remember that while a "normal" angle of view on a full-frame camera is about 24-70mm, on an APS-C camera it's about 17-55mm. In each case, anything longer is a telephoto lens; anything shorter is a wide-angle.

Re: EF-S v EF Lens - Crop Factor (Image Conversion Factor)

jrhoffman75 — Fri, 02 Oct 2015 20:25:45 GMT

"If I use an EF-S lens on a camera with an APS-C sensor, does the sensor capture all that I see in the viewfinder i,e, with a ratio of 1:1?"

The answer is a qualified "Yes". There is a slight difference since the viewfinder shows about 95% (so you may capture a little more, but you never cut anything off.)

http://digital-photography-school.com/crop-factor-explained/

Re: EF-S v EF Lens - Crop Factor (Image Conversion Factor)

Waddizzle — Fri, 02 Oct 2015 22:13:16 GMT

@jrjsmith wrote:
Good evening,

Please excuse me if this is a dumb question.

Joe.

My definition of dumb questions are the ones that you're too embarrassed to ask. Everyone has to learn some day, some way, and somehow. Ask away.

Actually, it's my understanding that both sensor types occupy similar positions inside of their camera bodies. Each one is centered in the exact same position at the center of the image projected by the lens. With a full-size sensor, the diameter of the round image that is projected is only slightly larger than the sensor.

Meanwhile, an APS-C sensor does not cover as much area, and will only capture what is in the center [cropped] of the projected image, which is why a full frame will have a wider field of view with the same lens. The net result is that the smaller sensor will seem to have more zoom, or focal length, compared to that same lens on a full frame body.

Why don't they just rate EF-S lenses with the equivalent focal length? Because the focal length refers to a physical dimension inside of the lens. The focal length specification is telling you about how the lens is made, not how it performs. It is up to you to understand how a given lens will perform on your camera body, which really isn't all that complicated...just multiply the focal length by 1.6.

Re: EF-S v EF Lens - Crop Factor (Image Conversion Factor)

ebiggs1 — Sat, 03 Oct 2015 01:42:15 GMT

The 'S' in the name EF-S stands for short focus. This is of no concern to the user. And the crop factor is also of no concern to the user. The camera crops nothing. It is a full frame in the sense of you get what you see in the view finder.

The term comes about because of old film camera that use 35mm film. Somebody wanted to know how to compare the two.

People don't really consider there iphones as crop cameras but they are. Just as much as a Canon Rebel is. Nobody calls a medium format camera and enlargement camera! But it would be if you used the same logic. Forget it.

It is far better to think in terms of 'angle of view' (AOV). This never changes no matter what camera you use. Example ... Any lens that give a 46 degree AOV is considered normal. It makes no difference which camera you use. This spec is included with every lens. MM tells you what the lens is. AOV tells you what it does.

Re: EF-S v EF Lens - Crop Factor (Image Conversion Factor)

jrjsmith — Sat, 03 Oct 2015 15:02:14 GMT

Many thanks for the link.

Re: EF-S v EF Lens - Crop Factor (Image Conversion Factor)

jrjsmith — Sat, 03 Oct 2015 15:03:57 GMT

Thanks for the clarification and for setting my mind to rest about the image captured vs the viewfinder image.

Now, I need to brush up on the AOV.

Re: EF-S v EF Lens - Crop Factor (Image Conversion Factor)

ebiggs1 — Sat, 03 Oct 2015 19:34:41 GMT

Try this one.

Re: EF-S v EF Lens - Crop Factor (Image Conversion Factor)

photosbylorenz — Tue, 23 Jan 2018 00:41:09 GMT

I'm new to this forum and this is exactly the info I was looking for. Thanks to those that have contributed. Well done.

I just want to make sure I understand it all completely.

I purchased a Canon 80D based on price and the dual pixel focus and such and the many recommendations I saw on Youtube. I do all kinds of video and the 80D seemed like a good all-around choice.

Now I am getting into real estate videos and photos. For the interior shots (stills and video), I need something in the range of a 14 to 16MM wide angle lens. My question...

Do I understand correctly that if it is an EF-S lens, whatever the focal length says on the lens will be what I see and if it is an EF lens, I need to mulitply the minimum focal llength by 1.6 to know th real focal length I will see?

So then, the EF-S 18 to 55 kit lens really will be 18mm and the EF 50 f1.8 STM that I just ordered will actually be an 80mm focal length (50 x 1.6 = 80). Please confirm I have it correct... whew.

THANK YOU.

Re: EF-S v EF Lens - Crop Factor (Image Conversion Factor)

jrhoffman75 — Tue, 23 Jan 2018 00:48:15 GMT

Focal length is a physical property of a lens. A 50mm lens has a focal length of 50mm whether it’s on a full frame camera, a crop sensor camera or sitting on a table unmounted to a camera.

When on a crop sensor camera the field of view is changed and a 50mm lens has the field of view equivalent to an 80mm lens on a full frame camera.

EF and EF-S lenses are the same as far as this behavior goes.

If you want to shoot interiors you want a 10mm or so lens on the 80D.

Re: EF-S v EF Lens - Crop Factor (Image Conversion Factor)

photosbylorenz — Tue, 23 Jan 2018 09:02:53 GMT

Thanks John. Not the answer that I was hoping for, but at least I understand it now and I will shop for a 10mm lens for my interior shots.

Re: EF-S v EF Lens - Crop Factor (Image Conversion Factor)

Waddizzle — Tue, 23 Jan 2018 10:31:51 GMT

@photosbylorenz wrote:
Thanks John. Not the answer that I was hoping for, but at least I understand it now and I will shop for a 10mm lens for my interior shots.

There are two wide angle Canon zoom lenses made for EF-S mounts, a 10-18mm STM, and a 10-22mm USM.

Re: EF-S v EF Lens - Crop Factor (Image Conversion Factor)

photosbylorenz — Tue, 23 Jan 2018 22:10:22 GMT

Perfect. Thank you!

Re: EF-S v EF Lens - Crop Factor (Image Conversion Factor)

ebiggs1 — Tue, 23 Jan 2018 23:05:42 GMT

Crop factor is a big joke. It is a meaningless term invented to slap on certain sensors because they had to come up with something.It is nothing short of confusing to most people. Even long time photographers think the crop sensor camera actually crops their image. People on all the photography forums will say so. It crops nothing! All camera no matter what size sensor they have are FF in the sense that you get what you see in the viewfinder, nominally.

If you notice they don't call P&S cameras "really cropped sensor". And they don't call medium format cameras "expando sensors".

Again if you have a 50mm lens and could put it on a P&S it would still be a 50mm lens. Even putting it on the medium format or large format body, it is still a 50mm lens.

A better way to think about it is "angle-of-view". There are charts that quickly tell you exactly what it is. On your 'crop sensor' body you need a 18mm to 16mm for a WA angle of view. A 14mm to 10mm is considered an ultra wide angle.

Re: EF-S v EF Lens - Crop Factor (Image Conversion Factor)

RobertTheFat — Wed, 24 Jan 2018 04:41:54 GMT

I agree with Ernie that angle of view is a more comprehensible comparison vehicle than crop factor. But I think it's even easier to simply learn how a given lens behaves on each type of camera. I've found that the only times I've had to actually consider a len's "full-frame equivalence" is when I'm planning a shoot with both a FF and an APS-C camera, to make sure I don't have a coverage gap.

Re: EF-S v EF Lens - Crop Factor (Image Conversion Factor)

kvbarkley — Wed, 24 Jan 2018 15:46:19 GMT

Back in the day, when 35mm film was dominant in the market, for better or worse, the focal lenghts of the lenses for the 35mm system became the standard nomenclature for a particular angle of view.

Along came APS (Which I liked by the way, it was a good bridge to digital, with a first stab at film based "EXIF", but I digress). Since all the major manufacturers had interchangeable lens APS systems, there had to be a way to explain that the angle-of-view of a 50mm lens for APS was different than for 35mm and crop factor was born.

Since the first digital bodies had APS sized sensors, it was natural to keep 35mm focal lengths as the "standard" and use a crop factor to get a handle on the angle of view.

I think it is a handy way to understand the angle of view for a particular focal length. To answer the question above, it only matters for interchangeable lenses.

Re: EF-S v EF Lens - Crop Factor (Image Conversion Factor)

photosbylorenz — Sat, 27 Jan 2018 02:33:31 GMT

Thanks for the walk through memory lane. I think I got it now. 35 mm (24mm x 34mm) was dubbed a standard and hence dubbed "full frame". Anything other than a "full frame" size is just a different frame size and hence has a different angle of view. A way to express the angle of view is to compare it to to the standardized "full frame" via a ratio or multiple, such as 1.5, 1.6, 1.35, etc.

Thanks to everyone that responded. Very educational,