APS-C VS Full Frame Lenses? (lens recommendation)

SuzukiGS750EZ · Oct 11, 2016

Hey guys. I know that when you buy a regular or "full frame" lens and use it on a crop sensor, you multiply the crop factor to get the focal length on that sensor. 50mm on a full frame becomes 80mm on my 80D. What i was wondering was, i see that they make APS-C specific lenses, some of which won't work on a full frame body. When they label these as say 55-250, is it 55-250 on a crop sensor or is it 55-250 in the full frame world while being 88-400 on a crop lens. I would think that 55-250 would be going by the 35mm standard, but i'm unsure since they're being marketed as APS-C. Hope this wasn't too long winded.

P.S. Can anybody recommend me some cheaper sub 200$ lenses (preferably 100-150$) for my 80D? I have an 18-55mm II kit lens from my rebel xti, the 75-300 III Non IS and the standard plastic 50mm II. I was almost thinking about ditching them all and looking for 18-55 in a better build quality, 55-250 and then maybe the 50mm STM/10-18MM STM kit canon is offering now. Ideas are fully welcome, i'm on a super tight budget. Just bought a MeFoto Roadtrip tripod, Canon 80D body, spare canon battery, canon battery grip, a camera backpack and a lexar professional 1000x 16fb SDXC memory card, so my funds are fairly tight at the moment. I want to get an 18-135 STM (really looking to get mostly STM with this camera, i have read that STM focus faster and produce almost no sound). USM used to be what i wanted but since STM came out i mays well put my money into that. I don't want to be buying mediocre lenses (i understand my budget doesn't really work with that) but i'm hoping someone can give me an idea.

john.margetts · Oct 12, 2016

SuzukiGS750EZ said:
Hey guys. I know that when you buy a regular or "full frame" lens and use it on a crop sensor, you multiply the crop factor to get the focal length on that sensor. 50mm on a full frame becomes 80mm on my 80D.

no, they don't. focal length stays the same regardless of the camera the lens is attached to.

SuzukiGS750EZ said:
What i was wondering was, i see that they make APS-C specific lenses, some of which won't work on a full frame body. When they label these as say 55-250, is it 55-250 on a crop sensor or is it 55-250 in the full frame world while being 88-400 on a crop lens. I would think that 55-250 would be going by the 35mm standard, but i'm unsure since they're being marketed as APS-C. Hope this wasn't too long winded.

The crop factor describes the field of view (FOV) of the lens and this changes regardless of the label, EF or EF-S. The FOV of the 55-250 lens on your 80D will be the same as a 88-400 lens would have on a full frame camera. Focal length stays the same.

OGsPhotography · Oct 12, 2016

You can probably get the UWA 10-18 second hand in your budget if @200+

For a 100$ budget I would suggest leave your camera home one night and take your wife|significant person out to dinner.

spiralout462 · Oct 12, 2016

I would use the lenses you have until you KNOW what focal length you need. That is the cheapest way to go about it. If you find a lens at a yard sale for 10 bucks, it's worthless if it's a focal length you don't use. Where is your current kit falling short?

The more modern versions of your lenses are slightly better quality but I doubt it's worth replacing them all with newer equivalent.

Piccell · Oct 12, 2016

You are getting the focal length and the effective focal length confused. The focal length never changes unless you change the length of the lens barrel as in a zoom lens, but the effective focal length will vary depending on the camera body and sensor format.

Lens makers state the actual focal length of the lens, if it is an FX lens and it is used on a DX body the effective focal length is different from the actual stated focal length. If it is a lens DX lens, the effective focal length will not be different from the stated actual focal length, however if it is used on an FX body it will have darkened fuzzy (vignetted) edges.

Does this answer the question?

If you are looking for a better lens and want to save some money, look at used lenses from rentals, and private party sales. I recently got a
AF-S NIKKOR 600mm f/4E FL ED VR Lens
used in like new condition at an estate sale for 1700.00.
While it's not a lens I will ever get much use out of (if any) it's nice to have and it could be sold for a lot more if I chose to sell it. (I won't, it's too nice looking and impressive.)

beagle100 · Oct 12, 2016

yes, focal length stays the same
on a crop the Canon 10-18 is good - $199 refurbished which includes the warranty

TCampbell · Oct 13, 2016

Focal length never changes just because you change sensor sizes. What focal length technically means is that the distance from the point where the lens first starts focusing the light inward, to the point where the image comes to focus, is some given distance... that distance is the focal length.

There are lots of properties associated with the focal length and these can be used in calculations.

However what DOES change when you use a smaller sensor is the "angle of view".

So the notion that putting a 50mm lens on an APS-C body with a 1.6x crop factor means it's really an 80mm lens isn't accurate... it's STILL a 50mm lens. But the "angle of view" on your images will resemble the angle of view that you would see if you had used an 80mm lens with a full-frame sensor body.

You could shoot with a full-frame sensor camera using the same 50mm lens and then "crop in" by 1.6x and get roughly the same effect... there are nuances such as pixel pitch (the APS-C camera usually has smaller "pixels" (really the sensor is covered in "photo-sites" because "pixels" are RGB and photo-sites are mono-color and have to be processed to create RGB but you get the idea.) So cropping wont get you an identical image but it'll be close.