How Camera Manufacturers and Reviewers Mislead or Lie.

[Ukastronomer (Jeremy)]

Originally Posted by Renato1

Thanks, but I have to disagree.

Most people don't know the size of their sensors, and are unlikely to be able to do the simple geometry you suggest. They may, however, be able to do the simple arithmetic to work out equivalancies using effective focal length and effective f number to match the actula results they see in their camera.
Regards,
Renato

I agree, I have not knowingly used geometry since I was in school 50 years ago.

[skysurfer]

Originally Posted by Ukastronomer

FF lenses work on Crop sensors crop sensor lenses will NOT work on FF, one of the biggest mistakes people make, they buy a crop camera, later want to shoot FF but have bought a load of crop frame lenses, BUY FF lenses for any camera as they fit both.

Not true.
Nikon DX lenses fit on FF bodies such as D750, D8xx, Z6 and Z7 (with FTZ adapter on the latter two), obviously cropping the FOV and reducing the megapixels by 2.25.
Same ithe Canon EF-S lenses on EOS R and RP (with EF adapter) but NOT on the EOS 1, 5 and 6 series, because the 'bum' of the lens touches the slapping mirror which does not happen on mirrorless.

[bojan]

Originally Posted by Renato1

You say that crop factor is idiocy, but you have not explained what arithmetically is incorrect about using crop factor - what wrong answer it gives in terms of describing image relative to a 35mm full frame sensor.
..

The problem is, the term is misleading to most new camera users, and completely un-necessary if just a minimum mental effort is added to grasp the concept of field of view.
BTW, why they took 35mm as standard? Who not something else? 60mm was also standard (especially among professionals).... or APS. (yes, I know - it was the fact most of cameras then were 35mm but "laziness factor" was also heavily involved).

As to why this is a problem now... basic arithmetic (geometry, in relation to FV of the camera/lens combination) is OK, but it doesn't take f/ into account.
We had a discussion here on this forum some time ago when someone start to apply crop factor in calculation of camera scale (arcsec/pixel), confusing couple of people in the process. His calculation was completely wrong, of course.

It is beyond me why some people are willing to spent huge amounts of money for the equipment, and then don't put any additional effort in understanding the basic physical/geometric principles on which that equipment works.

Suma summarum:

- 50mm lens is 50mm lens, was and always will be, no matter with what sensor size it is used.
- "Crop factor" is applicable to camera only... it should be avoided/rooted out (and explained to users properly every time why), as it becomes completely redundant once the basic optical geometry is properly understood (which in our hobby doesn't have alternative IMO)..

[SteveInNZ]

Originally Posted by Renato1

To illustrate, one example he gives is a Panasonic 12-35mm f/2.8 lens for a Micro 4/3s camera which has a 2X crop factor. Advertisers then say it's a 24-70mm f/2.8 full frame equivalent lens, when in physical fact it is a 24-70 f/5.6 full frame equivalent lens.

Well, in fact, it's not.
Which only goes to illustrate your point that crop factor is misleading and confusing.

The depth of field equivalent is f/2.8 to f/5.6 as you say, but the focal ratio is the same (f/2.8).

Take a bridge camera sensor as a wider example. It has a crop factor of 6 compared to a full frame. In terms of depth of field equivalency, you multiply the aperture by 6 but in terms of exposure, the true aperture is still the useful number. eg. If a scene requires an exposure at ISO 100 of 1/125 at f/5.6 with a full frame camera, it is 1/125 at f/5.6 with a crop camera or with a bridge camera.

So you can't make the blanket statement that the aperture value needs to be multiplied by the crop factor as it's just wrong.

Steve.

[Ukastronomer (Jeremy)]

Originally Posted by skysurfer

Not true.
Nikon DX lenses fit on FF bodies such as D750, D8xx, Z6 and Z7 (with FTZ adapter on the latter two), obviously cropping the FOV and reducing the megapixels by 2.25.
Same ithe Canon EF-S lenses on EOS R and RP (with EF adapter) but NOT on the EOS 1, 5 and 6 series, because the 'bum' of the lens touches the slapping mirror which does not happen on mirrorless.

FF lenses are "manufactured" to work on BOTH FF and Crop, the fact that you can compromise the quality of the image and end up with a crap photograph by using crop lenses that do not cover the full area of the FF sensor is pointless

The smaller lens coverage does not cover the full frame sensor, without then cropping

[gregbradley]

I don't see the issue.

The optics have a focal length and an aperture.

The sensor is a different item, separate from the scope.

You can have tiny sensors and large sensors.

Most scopes only handle sensors APSc or smaller hence the number of ASI cameras etc.

A few handle full frame sensors. Hardly any handle medium format.

The bigger the sensor the wider the image just like if you use a shorter focal length scope.

A small sensor only images a small slice of what the optics have on offer.

It can be handy though if the scope's optics are not able to give aberration free corners or bad vignetting that show up on full frame sensors.

I don't see what is misleading there. Its more the consumer needs to understand the effects of smaller or larger sensors on their image.

A small sensor creates the same effect as cropping part of a larger image created on the same optics by a larger sensor.

So much so that Sony and others now offer APSc or smaller crops of their full frame images in some cameras. Its similar to using a longer focal length lens but really is the same as cropping the image in post processing.

Greg.