Aperature on the Barrel of Lenses

Hey guys! I recently joined Photography Talk because I figured I could use a great group of people to support me through my photography journey.

I have been into photography for a few years now, and am getting ready to buy my first camera lens.

The camera I have been using up until now was bought by my parents a few years back, the Canon T5 Rebel. I have been considering upgrading to the Sony A7iii, but first need to get the lens situation figured out.

No matter where I try looking, I can not find a forum or article or YT video, explaining the numbers and everything on the barrel of the lens. Everyone says it is super important, but never goes into a ton of depth regarding what it does.

I understand that the aperature rating on the barrel of the lens means the maximum aperature for that particular lens, and I understand that the larger the aperature, the more light that lens can take in, but what I don't understand is does that "more light" only affect the lens when the camera is in that exact aperature that is on the barrel? Or does the maximum aperature affect all of the aperatures, meaning that there will be more light allowed into the lens no matter what aperature I am in, just because it has a higher aperature rating...

I hope this makes sense, I know it is sooo confusing, and even though I have been photographing for a few years now, I am just beginning to seriously understand everything. I really hope someone can help me out, because I have been dying to figure this out, and am so lost when it comes to purchasing a lens!

Thanks in advance!

No. The f/stop number is the ratio of the focal length of the lens (50mm, 35mm, etc) divided by the diameter of the "pupil" of the lens, the opening created buy the diaphragm blades through which light passes. A 50mm lens at f/4 will pass the same amount of light whether its maximum is at f/2.8 or f/1.4. But other factors affect the brightness of the resulting image, so that different lenses may well give different results at the same aperture .Hope this is useful. And, the Sony is a good choice, but I would opt for the better line of lenses.

Thank you John! I appreciate the help! So does a larger F stop make a difference when buying the lenses? That is the only part I am still confused on. And just so I can make sure I understood you correctly, if the barrel says 50mm f/4, that means that the lens CAN go to higher f stops then just f/4, like f/2.8, etc. Correct? Again, thanks for the help! I hope you can answer my above question too!

I think you are getting confused... The smaller the aperture number, the larger the opening, letting in more light and lessening the depth of field. Thus an F4 lens will go from F4 to F22 (sometimes F32) In order to open up to F 2.8, etc, it has to say it's an F2.8. Then the aperture can be set anywhere from F2.8 to the minimum. Lenses with larger F stops (like 2.8 , 1.8, etc. will command higher prices. Be careful of variable aperture lenses (almost all being zooms as opposed to fixed focal lengths) as they will open wider at the shorter focal lengths and close down as you extend the focal length out.

Ok, I think I understand now. I was getting really confused because 1) there is an f stop number for aperture on the lens, and then you can also adjust your aperture on the camera itself. So I was getting confused on what the point of a lower aperture number on the lens was if you're shooting at F/8, or F/12, etc. Which leads to why I was getting confused 2) because I almost never shoot at the highest aperture my camera can handle anyways. I usually shoot at about F/8 for real estate photography. I also shoot cars, which are shot usually at the highest aperture, but I haven't been shooting cars as often lately, and when I did, I did so in automatic mode. I am just starting to get into Manual and Aperture focused, etc. So I was extremely lost on it all. I think I've got it all down now, and it makes more sense.

Basically, if I'm shooting at my highest aperture (F/1.8 for instance), the camera will take in more light, and to put in lamest terms, my background will get more blurry, versus a lens that has the highest aperture of F3.5 or F5.8.
I can still adjust my aperture to whatever I want, say F/18, but the camera will obviously be taking in less light, and have a greater depth of field.

Let me know if I've basically got it down! I think I understand it all now, I feel much more confident shopping for lenses now then I did even 30 minutes ago!

I think you've got it now...

. And, on the question of how fast a lens you should get, it isn't so much a question of f/stop, but of quality of construction. That's where spending more is a good strategy. If you go with the sony AIII, consider the 24-70mm f/2.8, a great lens I own and like .

Here's an example. shot with that lens on the sonyAsII:

Rome-2019-Stroll-No9 by John Landolfi , on Flickr

Awesome! I will definitely consider this lens when making my next purchase! And I'll definitely be hopping on here again when I need help picking out more lenses! Thank you!!

Very welcome!