# Crop Factor. Something to consider when buying a lens when you are shooting other than FF.

Started Jun 6, 2014 | Discussions thread
Re: What about medium format or larger?

b0k3h wrote:

forpetessake wrote:

JackM wrote:

forpetessake wrote:

When they convert the focal length to the FF equivalent and conveniently forget to convert the f-stop as well they intentionally want to confuse the ignorant buyers blah blah blah

Except f2.8 at ISO 200 will meter the same shutter speed on FF, APS-C, m4/3, and on and on, so there is no need to convert f-stop.

And it looks you understood exactly nothing in this thread. What's your definition of the "need"? Is there a need to convert the focal length? Do you understand the equivalence? What it actually means and why do people do those calculations? I think not.

Furthermore, it is an immutable mathematical fact. Focal length divided by f-stop = aperture size, and that is that.

So what? You can divide or multiply anything upon anything, what's the meaning of it? What's the meaning of f-stop? Why is it important? You don't seem to know.

What's surprising in these forum discussions is not the ignorance per ce, it's the arrogance -- people are ignorant even about their ignorance, but they got somewhere the idea that they understand what they are talking about. No wonder they never learn anything.

maximum f-stop and fl are immutable properties of a lens, regardless of whether or not you choose to believe it.

just like the sun will always go up tomorrow, no matter how dark it is in your own little world.

NO THEY ARE NOT.  WHY EVEN BOTHER WITH THE F-STOP THEN.  WHY NOT JUST BUILD A LENS WITH A FIXED APERTURE AND LEAVE IT TO PEOPLE LIKE YOU TO ADJUST ONLY THE SHUTTER SPEED.  What is an immutable property of a lens???? I don't think you know what that word means.  The f-stop is exactly what makes the lens mutable.  It can be changed to create the look or feel of a photograph.  It works in synchronicity with the shutter and ISO value to create NOT JUST AN EXPOSURE as you would have everyone believe, BUT ART!!!

Is it your point to make everyone else here stupid, so that our photography will make yours look better?