What is a FAST lens?

[@forestchaput]

CORRECTION: at 01:18 there is a graphic showing the exposure triangle. The drawing of the different aperture sizes is incorrect and should show the largest opening at f/1.4 and the smallest at f/22.

[@roromboraragattv8390]

that' the first thing I saw...thanks for correcting this...

[@mtippett80]

Great video, super clear to understand!!

[@forestchaput]

Glad it helped!

[@mtippett80]

@@forestchaput and you got a new subscriber out of me 😊

[@garyoldham4449]

It might help to understand lens speed if you think about astrophotography. You want to zoom in on the extremely faint, a Faraway cluster or nebula object. You set everything appropriately and snap a shot. Of course you use the telescope mount, wide aperture, higher iso, and a slow shutter speed. The image is extremely faint. So you set a longer shutter speed. This helps. The longer the aperture is open the more light can be gathered to add up on the sensor. It's a matter of addition. A fast lens means it is capable of gathering more light; you don't need as long of a shutter speed to collect the same amount of light. A slow lens set for the same exposure time as the fast lens won't collect as much light as the fast lens. It will be fainter which is bad for photographing faint objects. Since the Earth is turning a longer shutter speed would start to show star trails, smear the image, and ruin the photograph on a stationary mount. This is not an issue if you have a good tracking mount which stays locked on the target. For terrestrial imaging it's really the same thing, a faster lens means you can get away with shorter shutter speed and still collect the same amount of light. So it relates to brightness. A fast lens collects light faster.

[@ebrahimsheriff9537]

Simply explained. Thank you!

[@forestchaput]

Happy to help!

[@Glurbschnurb]

Great explanation! I wish I watched this before buying my fx30 with a f4 bundled lens expecting awesome bokeh as a noob.

[@sawyerhaupt]

My Nikon z85 1.8 is my favorite lens, colors and sharpness is just amazing.

[@forestchaput]

That's a fantastic lens and the f/1.8 aperture at that focal length is perfect. 👌

[@forestchaput]

How fast is your fastest lens?

[@wooddogg8]

My nifty fifty... f1.8 so far

[@forestchaput]

Perfect!

[@kevywilliams3304]

There no hyper focus link

[@forestchaput]

Down in the description we have the link on hyperfocal focusing :) but here is the link again: kzbin.info/www/bejne/f3WuaK2Xi7B0ptE

[@CrashCarson14]

Why can't the aperture just be bigger? Nobody has ever explained the optics side on why it cannot just be made larger. Relative to the size on the lens. 50mm 1.7 is always a small lens. But wide aperture

[@forestchaput]

Great question! Focal ratio is simply the relationship between focal length and diameter of the lens opening. The faster the lens, the larger and heavier it needs to be. Eventually they just get too big to be useable.

[@charleskear9530]

Your diagram has an error look a f22 and the picture of the opening!

[@forestchaput]

You are right! Good catch. I’ll make a corrective comment. Thanks!