Does crop sensor effect the F stop?

The focal length is multiplied by the crop factor but someone told me also the f stop is increased?

If this correct?

So a 16mm f1.4 on a crop is a 24mm f2.2???

Neither the focal length or the aperture is affected physically by the sensor size.

There are other visual differences that are seen that lead many to think that the focal length is changed or fstop is altered. Those differences are due to framing differences and pixel density of the crop sensor vs FF sensor, and not because the focal length or aperture magically was altered by the sensor format.

Well I guess I want to be sure that the f stop is effected because I only thought the focal length is.

Will a 1.6 f stop lens Im buying end up not actually being a f1.6?

https://www.youtube.co​m/watch?v=f5zN6NVx-hY

PJmak wrote in post #18793596
Well I guess I want to be sure that the f stop is effected because I only thought the focal length is.

Will a 1.6 f stop lens Im buying end up not actually being a f1.6?

Yes you will be able to set it to f1.6 no matter what camera you use it on.

And Tony just continues to push the incorrect info in that video as about everyone else. The lens doesn't become "anything" on different bodies, the sensor cropping the image down gives that illusion.

70mm f2.8 lens on both a FF and Canon 1.6 crop... same exact exposure parameters on both (1/400, f2.8, ISO 6400)

1) FF on the left, crop on the right, the crop sensor tosses out all the image material outside the yellow box, nothing more.
2) Crop out that yellow box on the FF image after you take it, it is the same as what the crop sensor recorded.

So the simple answer is no, the focal length and aperture doesn't change. The more complicated answer is when you start to talk about pixel density on a smaller sensor vs larger, then equivalent framing on the FF to match the crop, which means you have to use a different FL, which then changes the DOF, which then means you change the aperture to get the DOF back, if you want an exact equivalent image from both. That is rarely the case, and hopefully we don't go down that rabbit hole for the 1,533,226 time.

More in focus with same lens on the crop sensor.
This is why MFT has advantage over FF. Lower ISO due to large apertures and still enough DOF.

Again, the answer is that a camera doesn't physically change the focal length or aperture of a lens, depending on sensor size.

We have enough other 200+ pages of threads that can go into the dissertations of equivalency of view, DOF differences due to aperture, focal length, distance, framing, etc but NONE of that has anything to do with what this person heard from someone about how a crop body changes the focal length and aperture of a lens. That simply isn't true, the crop camera just CROPS the image circle down to a smaller rectangle, at the same aperture as it would be on a FF.

Basically, with the crop sensor difference, is referring to the image area of the sensor being smaller. The focal length and f-stop do not change; you are just looking at a smaller area than what a full frame would normally see.

When talking equivalency, think of it this way.. a 50mm lens with a 1.5 crop factor on an APS-C camera, will give the image area that a full frame would see at 75mm. The equivalent f-stop does not change; it will be there equivalent of the full frame, with a cropped photo.. you still get the same amount of light in ON THE LENS (a full frame will still gather a bit more light on it's image sensor, due to a larger size).

Team Speed has it correct above.

txsizzler wrote in post #18793670
Basically, with the crop sensor difference, is referring to the image area of the sensor being smaller. The focal length and f-stop do not change; you are just looking at a smaller area than what a full frame would normally see.

When talking equivalency, think of it this way.. a 50mm lens with a 1.5 crop factor on an APS-C camera, will give the image area that a full frame would see at 75mm. The equivalent f-stop does not change; it will be there equivalent of the full frame, with a cropped photo.. you still get the same amount of light in ON THE LENS (a full frame will still gather a bit more light on it's image sensor, due to a larger size).

Team Speed has it correct above.

Yes. TS is correct. Where did this nonsense about crop bodies changing the f-stop come from?

PJmak wrote in post #18793596
Well I guess I want to be sure that the f stop is effected because I only thought the focal length is.

Will a 1.6 f stop lens Im buying end up not actually being a f1.6?

If you started with a 50mm f/1.8 lens, it will STAY a 50mm f/1,8 lens. What DOES change...
The FL stays the same, but it BEHAVES AS IF you were using a 1.6x longer FL, that is...

1. Due to the tighter framing when shooting with APS-C (compared to shooting with same lens on FF), your DOF is shallower.
   
2. In order to get the 'same DOF' as shooting 50mm f/1.8 on FF, you would need to use a smaller aperture by 1.6X with your APS-C camera
   
3. that is, in order to get 'same DOF' as 50mm f/1.8 aperture on FF, you instead need about f/2.8 with your APS-C framing.
   

TeamSpeed wrote in post #18793612
And Tony just continues to push the incorrect info in that video as about everyone else. The lens doesn't become "anything" on different bodies, the sensor cropping the image down gives that illusion.

No, that just you wanting to be overly dramatic about the whole thing. Stop analyzing every single word. He is not wrong and NOWHERE in that video does he claim that the camera is physically changing the lens. That's just you wanting to argue a statement down to the finite detail instead of just adding some common sense and understanding whats being said.

At 1:47 he says this lens FL now becomes this other FL, which is the exact thing everyone translates to "a crop body changes the lens focal length", so no I am not being dramatic, he is wrong with his choice of words and propagates the myth that a crop body changes the FL.

I typically like Tony's material but not parts of that video, and am not part of Tony's bromance circle.

'FL' never changes due to mounting lens on a different format body.
'Aperture' or 'f/stop' never changes due to mounting on a different format body.
'FOV' does indeed change due to mounting lens on a different format body.
'DOF' does indeed change due to mounting lens on a different format body.

No it doesn't change neither focal length nor f-stop.

HOWEVER, if you want to use "equiv" numbers (i.e. "gives equiv of 35mm F/2 on FF") then yes you should multiple both the focal-length and f-stop. There is a time when talking equiv numbers makes sense.

Scoobert wrote in post #18793710
No, that just you wanting to be overly dramatic about the whole thing. Stop analyzing every single word. He is not wrong and NOWHERE in that video does he claim that the camera is physically changing the lens. That's just you wanting to argue a statement down to the finite detail instead of just adding some common sense and understanding whats being said.

It's still a bad idea to use focal length as a proxy for FOV. It keeps people from understanding, as bad terminology often does.

Anyway, a narrower FOV is *not* a positive thing, by itself. You can take black paint and cover 19.8MP of your FF camera's 20MP with black paint and leave just a 0.2MP crop in the center, with a FOV that is 10% as wide, like a lens with 10x the focal length. What has one accomplished, doing this? All one has done is thrown away more of the image circle, much like cutting down a full-image print to a small rectangle with scissors.

Now, if you have higher pixel density and/or less noise with a smaller sensor, then you have something useful, but not altered f-ratios or focal lengths.