Need info on my grand daughter's EOS Rebel T7 lens dimensions

[showme]

My teen granddaughter recently got a Canon EOS T7 Rebel with an EF518 55mm. She's volunteered to be a photographer for the school newspaper, so my wife and I wanted to get her some lens equipment for Christmas. My wife handled the search and purchase of a lens set that she found on amazon that stated they fit the T7, along with a list of others.

It seems that my granddaughter's camera's lens base is smaller than the one's we ordered. They are 58mm, and as far as I can see, when I measured her camera (she didn't have the manual with her, and wasn't sure where to find the base measurement on her camera), I found it is 50-51mm in diameter, depending if I used the inside diameter (50mm) or estimated the thread depth diameter (51-?). So, after doing a little research, I see there are 50mm lenses, but I'm a little mixed up here, since the box that her camera came in states the zoom lens is 55mm(??). 

What does this 55mm dimension indicate, the lens diameter or the base diameter? And, would her camera's lens base be considered 50mm or 55mm? I really can't see another 5mm of thread depth on top of the 50mm inside diameter of the camera's female lens base receptacle. So, as a no-nothing grandfather of a future photography nut, I'm asking all the experts here (i.e., anyone who knows more than me about these things) for help to figure out exactly what we need to get her. Btw, I realize we could wait until Christmas break is over and have her ask her instructor about it, but she was so disappointed when she found out she wouldn't be able to use it this week, I wanted to find one that fits her camera asap. This is what my wife ordered, and is now being returned. Their bases were too big to screw into the camera.

Thanks for any and all comments and suggestions on this. I appreciate it. Lee

[Commercial link removed per community guidelines and replaced with screenshot to serve as a visual aid.]

[showme]

Thank you, John! I'll definitely look these up and share this with Kate. My kids and grandkids have always looked up to me as "the one who can do anything!" (so they think), although they don't realize that to find the things I "know", I spend hours and days researching the things that I don't know, just so I can help with something. Thank you. I'm sending this to Kate, as well. Lee

[shadowsports]

Lee ,

Happy holidays to you and your family.  Lots of friendly, knowledgeable people here and we're happy to answer any questions you or your grandaughter might have.

[showme]

Well, after talking to my granddaughter about this, and showing her a few lenses I'd found and asking her what her class instructor uses, we decided to get her this lense- Amazon.com : Canon EF 75-300mm f/4-5.6 III Telephoto Zoom Lens for Canon SLR Cameras : Digital Slr C...

She confirmed, as I've read, that her camera is a little hard to focus at times, so I'm hoping this will help that, too. As I've said before, I'm pretty ignorant in this field, although Kate's aunt and uncle (my two other kids) have both been into photography since college, her mom, our youngest who is 37, hasn't taken it up. You all have been a big help, and I thank you again. I would appreciate any comments on this lens and why it is or isn't a good pick for Kate. BTW, Happy New Year! Lee

[shadowsports]

Hi Lee,

I really believe she would be better served with the EF-S 55-250.  Note that none of us mentioned the EF 75-300 which is a entry level lens and not one of Canon's best endeavors.  The 55-250 is about double the cost and for good reason. 

Please consider the following:

The 55-250 is an APS-C lens designed for the sensor in her camera.  There is nothing wrong with using a lens intended for full frame on a APS-C based camera.  {Edited for clarity.]

The 55-250 has image stabilization, the EF 75-300 does not.  IS is extremely helpful when shooting handheld at longer focal lengths. 

I'm not sure what her instructors' reasons are for recommending this lens.  The only thing I can assume is its rock bottom price.

Where to purchase Canon gear.  List of Authorized Dealers.  If in doubt, you can always check here:

Canon Learning | Authorized Dealers | Canon U.S.A., Inc.

Woodland Hills Camera is an Authorized dealer

[johnrmoyer]

According to that list, Amazon.com is also an authorized dealer. But one must check for "Sold by Amazon" instead of sold by a seller that is not on the list.

I agree that the EF-S 55-250mm f/4-5.6 IS STM is a much better lens. It is sometimes available refurbished at  https://www.usa.canon.com/shop/p/refurbished-ef-s-55-250mm-f-4-5-6-is-stm

[kvbarkley]

"There is nothing wrong with using a lens intended for full frame on a APS-C based camera, but it does change the field of view. Not a bad thing, just something to be aware of."

I hate to get into this on a thread for a newbie with a lot of good answers, but this is not true. On an EF-S camera, the EF 75-300 when set to 75 mm will have the exact same field of view as the EF-S 55-250 set to 75mm. I am not sure what you are saying here.

[Tronhard]

I wonder if this is a case of semantics or interpretation, and you may both be trying to say the same thing, but terminology gets in the way. 

Any lens, no matter if it is an APS-C or FF no matter what it says on the lens, on a crop sensor camera will have a Field of View reduced by the crop factor, resulting in an Equivalent FL that is 1.6x the lens physical one.  This is my article on the topic.
Equivalence 

[kvbarkley]

But this person has never shot with a full frame camera. Why should they care about equivalence?

[rs-eos]

It's useful to know if wanting to pick up new lenses based upon seeing what others are capturing.

e.g. an owner of a crop-sensor camera may see an image online of a landscape tagged with 14mm and camera used being full frame.  The owner likes how much of the scene can be captured, so picks up a 14mm lens.  But is now disappointed that it's not as wide (since FOV equiv is 22mm).   So if they know about the crop-factor, they'd then know to get a lens around a 9mm focal length.

[Tronhard]

It was a response to your post , which was itself a response to shadowsports, for your attention