# Need help, Please " the Lens factor of EOS-M ?"



## surapon (Oct 18, 2013)

Dear teachers and Friends.
Just 2 questions for EOS-M, Sir = EOS-M have Sensor =22.3 x 14.9 mm (APS-C size), But When we use EF. Lens, We must use Adaptor to make the Back of EF. lens far away from APS-C sensor, The Question is, If I use EF Lens, Can I use 1.6 Lens Factor to multiply my EF Lens at EF-M mounted ? ( EF 85 mm X 1.6 = 136 mm. of EF-M= ?).

The Next Question = For use the EF to EF-M Adaptor, Yes, We can use both EF and EF-S mount to this Adaptor and shoot with EOS-M----How can We use EF-S with the same space distant from the back of EF-S lens to the APS-C sensor, and work---BUT Can not mount EF-S Lens on Full Frame Sensor Canon EOS Cameras----In the reverse, We can use all EF Lenses on the SOS Body / Small sensor like 7 D .???
??, May be, Canon try to trick us, Not let us use the cheap FE-S Lens on the high cost FF Cameras ???.
Thank you, Sir.
Surapon.
PS--No I do not buy EOS-M right now, and wait for another 4 months to get EOS-Mh MK II ( h = high level---Not Standard )


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## neuroanatomist (Oct 18, 2013)

The 1.6x crop factor applies to all lenses mounted on the EOS M when comparing to the same focal length on a FF camera. 

EF-S lenses have an image circle that's smaller than the FF sensor.


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## surapon (Oct 18, 2013)

neuroanatomist said:


> The 1.6x crop factor applies to all lenses mounted on the EOS M when comparing to the same focal length on a FF camera.
> 
> EF-S lenses have an image circle that's smaller than the FF sensor.




Thank you, Sir , Dear Teacher, Mr. neuroanatomist.
Nice to learn from you again.
Have a great weekend, Sir.
Surapon


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## rs (Oct 18, 2013)

surapon said:


> The Next Question = For use the EF to EF-M Adaptor, Yes, We can use both EF and EF-S mount to this Adaptor and shoot with EOS-M----How can We use EF-S with the same space distant from the back of EF-S lens to the APS-C sensor, and work---BUT Can not mount EF-S Lens on Full Frame Sensor Canon EOS Cameras----In the reverse, We can use all EF Lenses on the SOS Body / Small sensor like 7 D .???
> ??, May be, Canon try to trick us, Not let us use the cheap FE-S Lens on the high cost FF Cameras ???.


EF-S has an identical 44 mm flange distance to EF. However, EF-S lenses are specifically designed to create an imaging circle which is not big enough for a 36x24 mm frame. In a bid to prevent strong mechanical vignetting, EF-S lenses have a plastic bung at the back preventing mounting on an EF mount body. This has a second advantage - these lenses can be designed to poke deeper into the body into the area where the larger FF mirror would otherwise clash, allowing some wide angle EF-S lenses to be slightly less retrofocus than the same focal length FF lens would be.

I have tried my Canon EF-S 10-22 on my 5D mk II - I had to pull the bung out of the back of the lens, and as long as the lens is zoomed into about 12mm or longer the mirror doesn't hit. From about 13mm onwards, with no filter there's no mechanical vignetting, and at no focal length or aperture is the corner performance anything but beyond a joke.

EF-M has an identical sized sensor to EF-S bodies, but due to the lack of mirror the flange distance is just 18 mm. All that's needed to make an EF-S lens fit then is a 26 mm long spacer with the appropriate mount at either end. The sensor size and position relative to the lens is then identical to an EF-S body. The adaptor also takes EF lenses, in much the same way as an EF-S body does.


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## surapon (Oct 19, 2013)

rs said:


> surapon said:
> 
> 
> > The Next Question = For use the EF to EF-M Adaptor, Yes, We can use both EF and EF-S mount to this Adaptor and shoot with EOS-M----How can We use EF-S with the same space distant from the back of EF-S lens to the APS-C sensor, and work---BUT Can not mount EF-S Lens on Full Frame Sensor Canon EOS Cameras----In the reverse, We can use all EF Lenses on the SOS Body / Small sensor like 7 D .???
> ...



Wow, , Wow, Wow---Thank you, Sir. Dear Mr. RS.
Thanks for the great infor. that I do not know before----Yes, I just a Average shooter for the recorded Photos and do not know the Fact behind the Design.
Nice to talk to you, Sir.
Surapon.


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## surapon (Oct 19, 2013)

Dear Sir.,
Another Stupid question. For All Point and shoot compacted Canon Cameras and EOS-M----The Kit Lenses that come with the cameras that have the MM. Print on the front of lenses such as 22 mm, And My Lovely Canon SX 160 IS = 5.0- 80 mm.------That number of MM. must Multiply by 1.6 Lens factors for real life situation = Right ?.
If It right---- all the Camera company must lie to us 5.0-80 mm are not right any more , must be = 8 - 128 mm. in the real situation of the shooting.
Thank you, Sir/ Madam.
Surapon


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## neuroanatomist (Oct 19, 2013)

surapon said:


> Dear Sir.,
> Another Stupid question. For All Point and shoot compacted Canon Cameras and EOS-M----The Kit Lenses that come with the cameras that have the MM. Print on the front of lenses such as 22 mm, And My Lovely Canon SX 160 IS = 5.0- 80 mm.------That number of MM. must Multiply by 1.6 Lens factors for real life situation = Right ?.
> If It right---- all the Camera company must lie to us 5.0-80 mm are not right any more , must be = 8 - 128 mm. in the real situation of the shooting.
> Thank you, Sir/ Madam.
> Surapon



The 'crop factor' depends on the sensor size, relative to FF. For example, the PowerShot S100/110 have a 4.6x crop factor. They aren't lying, though. If they printed 24-120mm on the lens of the S100, that would be a lie. 5.2-26mm is the actual focal length of the lens. Focal length is 'measured' as the physical distance between the lens' exit pupil (an optical point that may or may not be within the physical space occupied by the lens, depending on the lens design) and the image plane (where the in-focus image from the lens is projected), with the lens focused at infinity. So, focal length is an intrinsic property of the lens, regardless of the sensor size.


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## surapon (Oct 19, 2013)

neuroanatomist said:


> surapon said:
> 
> 
> > Dear Sir.,
> ...



Thousand Thanks, to my Dear Great Teacher Mr. neuroanatomist
You teach me again this morning.
Yes, If I do not know, and do not want to ask, That will make me more stupid in my whole live.
Have a great weekend, Sir,
Surapon


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## rs (Oct 19, 2013)

http://en.wikipedia.org/wiki/Crop_factor#Common_crop_factors


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## surapon (Oct 19, 2013)

rs said:


> http://en.wikipedia.org/wiki/Crop_factor#Common_crop_factors



Wow, THANKSSSS, Dear Mr. RS.
Great Link for me and some of our friends to learn this infor. from the great links that you provide.
Have a great day, Sir.
Surapon


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## Don Haines (Oct 19, 2013)

On some cameras you get both...

On the SX-50, the front of the lens states 4.3-215mm, and on the lens barrel, as it zooms out, you can read lines from 24mm to 1200mm, with writing at the end stating "35 mm equiv."


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## surapon (Oct 19, 2013)

Don Haines said:


> On some cameras you get both...
> 
> On the SX-50, the front of the lens states 4.3-215mm, and on the lens barrel, as it zooms out, you can read lines from 24mm to 1200mm, with writing at the end stating "35 mm equiv."



Wow, Thank you, Sir, Dear Mr. Don.
Some one have a great thinking, to not us sue the company.
Surapon


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## fsgray (Nov 11, 2013)

So I'm making the quantum leap from 35mm film cameras to the EOS-M. It would seem from this discussion that I would need to make two calculations to translate to my old frame of reference with film cameras to native EOS-M lenses. First is the 1.6x crop factor discussed above.

Second seems to be the "M-factor" due to the closer distance between the lens and the sensor of mirrorless cameras. Thus, the 22mm EOS-M kit lens would have a 1.6x crop factor PLUS a 1.42(?) "M-factor" making the kit lens give the same field of view as a 50mm lens of a 35mm film camera. Is this correct?


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## privatebydesign (Nov 11, 2013)

fsgray said:


> So I'm making the quantum leap from 35mm film cameras to the EOS-M. It would seem from this discussion that I would need to make two calculations to translate to my old frame of reference with film cameras to native EOS-M lenses. First is the 1.6x crop factor discussed above.
> 
> Second seems to be the "M-factor" due to the closer distance between the lens and the sensor of mirrorless cameras. Thus, the 22mm EOS-M kit lens would have a 1.6x crop factor PLUS a 1.42(?) "M-factor" making the kit lens give the same field of view as a 50mm lens of a 35mm film camera. Is this correct?



No it isn't.

A 22mm lens on the EOS-M gives you the same fov as a 35mm on 135 format film. Flange distance has got nothing to do with crop factor.


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## neuroanatomist (Nov 11, 2013)

fsgray said:


> So I'm making the quantum leap from 35mm film cameras to the EOS-M. It would seem from this discussion that I would need to make two calculations to translate to my old frame of reference with film cameras to native EOS-M lenses. First is the 1.6x crop factor discussed above.
> 
> Second seems to be the "M-factor" due to the closer distance between the lens and the sensor of mirrorless cameras. Thus, the 22mm EOS-M kit lens would have a 1.6x crop factor PLUS a 1.42(?) "M-factor" making the kit lens give the same field of view as a 50mm lens of a 35mm film camera. Is this correct?



There's no 'M-factor'. Just multiply by 1.6x. The 22mm f/2 pancake gives the FoV of a 35mm lens on FF (35mm film), and the DoF of f/3.2 (if you frame the scene the same, and that's because you'd be further away with 22mm on the EOS M than 35mm on FF, and more distance means deeper DoF).


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## bainsybike (Nov 11, 2013)

neuroanatomist said:


> There's no 'M-factor'. Just multiply by 1.6x. The 22mm f/2 pancake gives the FoV of a 35mm lens on FF (35mm film), and the DoF of f/3.2 (if you frame the scene the same, and that's because you'd be further away with 22mm on the EOS M than 35mm on FF, and more distance means deeper DoF).



Is that correct, Neuro? You'd be further away with the M if you were using the same lens on both cameras, but in the above scenario won't both cameras be at the same distance?


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## neuroanatomist (Nov 11, 2013)

bainsybike said:


> > There's no 'M-factor'. Just multiply by 1.6x. The 22mm f/2 pancake gives the FoV of a 35mm lens on FF (35mm film), and the DoF of f/3.2 (if you frame the scene the same, and that's because you'd be further away with 22mm on the EOS M than 35mm on FF, and more distance means deeper DoF).
> 
> 
> 
> Is that correct, Neuro? You'd be further away with the M if you were using the same lens on both cameras, but in the above scenario won't both cameras be at the same distance?



True, I didn't phrase that very well…sorry. 22mm on FF vs APS-C, you're further away on APS-C so DoF is deeper. 22mm on APS-C vs. 35mm on FF, you're at the same distance, but the focal length is shorter on APS-C, so DoF is deeper.

Bottom line, the FF equivalent of the 22mm f/2 on APS-C (i.e. EOS M) is a hypothetical 35mm f/3.2 lens.


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## bainsybike (Nov 11, 2013)

Thanks, Neuro!!


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## fsgray (Nov 11, 2013)

neuroanatomist said:


> Bottom line, the FF equivalent of the 22mm f/2 on APS-C (i.e. EOS M) is a hypothetical 35mm f/3.2 lens.


Okay, thanks! I've learned so much in the last few weeks, catching up with technology. I'm really impressed with this kit, such quality in such a small package compared to the old days!

Funny that the only prime available for this camera is a wide angle. I sure would like to see a telephoto prime. Even the zoom only goes to 55mm. I'm starting to look at 85mm lenses plus the adapter. There don't seem to be any reliable rumors of anything EOS-M of interest.


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