Yes... this is why you have to use the Crop Factor twice... if you only use for the focal length and not for the aperture, then you get a different equivalent lens.

You can do a very simple experiment with a pinhole camera: the focal length is simply the distance of the hole to the film (or screen or sensor or whatever).

If you use a crop sensor, then you simply use a part of the image circle and get a "sub-circle". To enlarge the same "sub-circle" to illuminate the whole sensor you have to move the hole farther from it... and you get a darker image.

So the "equivalent lens" (which is the same hole moved away from the sensor) has a larger focal distance, and because the hole is the same, you get a different F number.

Who is Tony Northrup?

It's a simple calculation (Math 101): the F number stays for "FACTOR", which means the division:

Diameter_of_the_hole
---------------------------
Focal_Length

This is why is expressed as f/xx which means 1/xx. So if you have a lens with 500 mm focal length and a hole of 50 mm, this lens will have and F number of 50/500 = 1/10 of f/10.

If you use a portion of the sensor by "cropping" it, then to get the same image on a FF, you should use a lens which has:

Diameter_of_the_hole x Crop_Factor
---------------------------------------------
Focal_Length x Crop_Factor

... so everything stays the same (it's the same lens, remember??)

This is why you MUST use the crop factor both on FL and F number.

You can see it the other way round: if you use a part of the sensor, the "equivalent FF lens" should spread the light on a larger area, so it is less light density (mW/mm2 or e- / uM^2).

Recently, I submitted this photo, and as always I ask for comments. All the comments were favorable, but there were two comments noted that the signature was intrusive and takes away from the photo impact. Now, I'm not complaining or whining as I know the comments were passed on with all good intent. However, I am curious as to what makes it intrusive. Is it the size, color, or??? Does it appear that I'm trying to advertise my work? Or does it bother you at all? It's only been recently that I started to sign them, and only those that I'm particularly proud of. I know there are several other Hoggers that do the same.

So as I said, the comments about the signature were meant for positive feedback and I appreciate the time spent carefully looking the photo over. So, no harm done. I'm always open to suggestions that will improve my work.

Your thoughts? I would appreciate your consideration. Ken

My dear husband bought me a new computer for Christmas, and now I’m scratching my head on how to move my Lightroom photos. My old computer is a 2011, 27” iMac . The new one is a 2019, 27” iMac.

I went to Adobe, and understand about canceling the subscription on the old computer, and enabling it on the new one. That is the limit of my knowledge. How do I move the photos from my old computer to my new one? Most (not all) are saved to an external hard drive, which I need an adapter to even attach to the new computer, as they no longer have USB ports.

Once I cancel the subscription on my old computer, (which I must do in order to put it on my new computer) are my photos even accessible on it? Will I need to duplicate all of my catalogs on the new computer in order for the photos on my external hard drive to even be accessible? What about the photos saved to the hard drive of the old computer, how to move them?

I’m sure that I am not the first person to have these questions, and I couldn’t think of a better place to get my answers than here.

Thanks in advance.