Effects of non EF-S Lens

[yeleek]

Hi,

I've recently purchased the 350d lens kit. Just wondering what are the effects of using a non ef-s lens on a Dslr? I've heard about a magnification issue (x 1.6?) but i just wondered if there was any image distortion or negative effects to be expected? Would any negative effects be more obvious with a non-canon lens?

Thanks

[Andy_T]

Yeleek,

welcome to the forum!

The magnification factor affects all lenses ... EF and EF-S alike.

Read here for some good explanation of it:
Understanding the DSLR magnification factor (http://luminous-landscape.com/tutorials/understanding-series/dslr-mag.shtml) on http://luminous-landscape.com.

Actually, the magnification (or crop) factor has 2 positive effects:
- most lenses are best in the center, and not so good (sharp) in the corners.
Because of the crop factor, only the center is used for the picture, and you get better results from your lens.
- Compare the price of a 200/2.8 lens with that of a 300/2.8 lens :shock:
The 200/2.8 on the 350D 'behaves' nearly like the 300/2.8 on a film camera.

The negative effect is also clear:
- if you want to have the same wide angle as with a 24 mm lens on a film body, it gets really expensive :confused:

Best regards,
Andy

[booggerg]

The EFS lens is just a bit lighter.. right??

What other benefits of EFS promoted Canon to come out with a new mount system?

[Andy_T]

Basically the possiblity to build lenses (especially: wide angle lenses) less complicated, smaller, lighter and less expensive.

Best regards,
Andy

[booggerg]

How does the EFS design allow them to build wider lenses? the crop factor still applys right?? the 10-22 on a XT body is really 16-22*1.6 right?

[martook]

booggerg: Since it's "impossible" to build a 10-22 for full frame, the EF-S design allows them to build it for just the 1.6x crop cameras.

No, the 10-22 is 10-22*1.6 :)

The "best" thing for all 1.6x crop camera users would really be to have only EF-S/Sigma DC and so on... because when you buy an EF lens, you pay a lot of money for parts of the lens you will never use (if you never get a full frame that is), and you have to carry around lenses that are a lot heavier than they need to be.

[slin100]

How does the EFS design allow them to build wider lenses?
For short focal lengths significantly less than the camera body's lens registration (distance from lens mount to sensor), retrofocus lens designs must be employed. The rear element on a non-retrofocus, short focal-length lens would bump into the mirror!

The lens registration of the Canon lens mount is 44mm. I'm not sure what the maximum distance a full-frame reflex mirror extends to as it swings, but it's probably safe to say that all lenses with focal lengths less than 40mm are retrofocus.

DSLRs with EF-S lens mounts have smaller reflex mirrors, so EF-S lenses can be designed with a shorter backfocus (the distance from the lens' rear nodal point to the sensor). The S in EF-S stands for Short Backfocus, BTW. Shorter backfocus allows the lens designer to employ less radical (i.e. smaller) retrofocus lens elements. I would bet that a mythical, non-EF-S 10-22 lens would have a huge retrofocus lens element.

[Edit: I forgot to mention that the smaller-sized image sensor also frees up the lens designer to scale down the size of the lens elements!]


the crop factor still applys right?? the 10-22 on a XT body is really 16-22*1.6 right?
In terms of FOV, yes.

[CyberDyneSystems]

Yes.. the -X- Factor still applies.

It's just less expensive wider lenses...
On say a msall pocketable Olymous point and shoot camera.. the lens may be 7mm or wider (of course with the extreme "crop factpor of such a tiny sensor.. it gives a feild of view of a 38mm).. easy to make.. and cheap.. but make a 7mm wide enough for 35mm film? Super pricey.

[ttmatsu]

Adding on to what CDS and slin100 wrote, EFS lenses take advantage of the APS size sensor and create lenses that only cover the APS size rather than full frame 35mm. So they use can smaller diameter lenses within the body of the lens making it less expensive and lighter (but still charge the Canon premium). Just look at the higher end P&S cameras. The Panasonic FZ20 has a Leica 35-420 f2.8 zoom that is just incredible. It's a constant f2.8 with great optical quality and because they only have to provide enough glass to cover the tiny sensor on the P&S, they can offer it on the camera for less than $600. If Leica built that same f2.8 constant lens in an EF mount (full frame), the lens by itself would be thousands of dollars and probably weigh 6 pounds. The front element would be huge.

No, there is minimal difference between a high quality 3rd party lens and a high quality Canon lens in optical quality. Some Canon L lenses are incredible and others are just very good. Some Sigma EX/Tokina Pro/Tamron lenses are incredible and others are just fair. You have to know what you are buying in terms of the particular model and how it compares to it's competitors and check for sample variation.