What the Numbers on your Lens Mean

What the Numbers on your Lens Mean

Some things seems pretty straight forward and like they’re common knowledge, but I’ve run into this a few times with my students that feel embarrassed to ask what all the numbers on the lens mean. There is no reason to feel stupid or embarrassed if you don’t know this, it is sometimes confusing. So I’m going to run through them one by one.

Common settings seen on newer digital lenses


If you have a zoom lens you will have a ring that turns to zoom in and out and it will also indicate what focal length you are currently set to. For example of your lens is a 70-200mm like mine you may see this which indicates I’m at 100mm currently.


If you are using a prime or fixed lens you won’t have a zoom ring, it will simply indicate the focal length on the lens barrell, as you see on my 85mm lens below.



The maximum aperture is the largest opening (the smallest number) on the aperture scale that your lens is capable of opening to.  Larger apertures like f2.8 or even f1.8 are highly desirable because they let in more light and allow you to shoot in low light conditions without getting camera shake.  (for more on that read 5 Tips for getting sharper images or Why the 50mm lens is your new best friend) This will vary from lens to lens and you may actually see a range of numbers such as 3.5-6.3.

You can usually find this information in one of two places on your lens, or perhaps even in both places:

  1. right on the end of the lens barrel on the edge
  2. on the front of the lens inside the filter ring area.

In the example below you can see two different lenses.  My Tamron 17-35mm (notice the focal length range is shown there also) and my 85mm. On the Tamron you see “1:2.8-4” and on the 85mm you see “1:1.8”.   What that means is that the maximum aperture on the 85mm lens is f1.8, but on the Tamron zoom it changes from f2.8 to f4 as you zoom the lens.  At the lenses widest, 17mm, I can open the aperture to f2.8, but if I zoom all the way in to 35mm now my maximum aperture is only f4. This is pretty common with kit lenses and ones that have a large focal length range such as 28-300mm or 18-200mm.



Some lenses, not all digital ones have this now, you will see a range of distances – usually marked in two scales, feet and meters. Look for the infinity symbol at one end, the other end will show how close your lens can focus, or its minimum focusing distance. Some lenses have built in MACRO settings which allow you to get a bit closer. They aren’t a true macro and you can’t get in super close but it’s a handy thing to have if you want to get closer without the expense and weight of an extra lens.

In the two lenses below you can see the scale on the Tamron (on the right) is in the outside of the lens and on the Canon 70-200 you can see it inside under a cover. Both will move if you manually focus your lens (**note: please remember to turn off auto focus if you do this because turning the focusing ring while autofocus is on can damage the gears and mechanisms inside your lens**)



Also on the end of your lens you may see a funny symbol that looks like a zero with a strike through it, then a number.  That indicates the diameter of the front of your lens or the size of filter required to fit on it. You can also find that same number on the back side the lens cap, see below – for this lens it is 77mm. Handy to know if you want to go to the camera store to buy a filter, or you’re buying something online.


Less common settings often seen on older manual focus lenses


This is one that you may or may not have on your lens, most newer digital lens do not have this as the aperture is set and controlled by the camera body now. Back in the days of film and manual focus lenses, the shutter speed was set on the camera and the aperture was set on the lens. You can pick up some great deals on older film lenses for specialty uses like macro, or fixed lenses with large apertures often for a fraction of the price of a new digital lens (you just need to get a special mount adapter ring to attach them to your camera). Just be aware that they will be manual focus and some of them you have to set the aperture on the actual lens itself. If you have one of these it may look something like either of the ones below:


This is a bit of a trickier one to find and explain. If you have all zoom lenses, you will not find this on your lens. If you have a prime lens, especially an older model you may see an extra ring of numbers on your lens such as in the image below (the numbers in the middle radiating out from the central orange line).

The numbers on the lens above represent (in order from top to bottom ring)

  • the distance scale
  • the hyperfocal distance scale
  • the aperture ring that actually sets the lens aperture

You use the hyperfocal distance scale to know which parts of your image will be in focus at different aperture settings. Notice the lens above is set to f16 and it is focused at 5m (15 ft). Now look at the middle scale and go to f16 on the left side of the orange line – that is indicating the closest point that will be sharp when focused at that distance, using that aperture – in this case it looks like about 2.75m (approx. 9ft). Now look at the f16 on the right of the orange line and you see it’s at infinity. So what we can tell from this is that at f16 we can get from about 9ft to infinity in focus, but the trick is to focus in the right spot.

Using the hyperfocal distance scale you’d actually put the infinity mark at the f16 mark on the right and that will give you the most depth of field possible at f16 (notice you don’t actually focus ON something, you set it on the lens by the numbers).  Note:  if you focused on infinity you’d only get from about 15ft to infinity in focus (estimating here) or if you focused at 7ft you would not get infinity sharp.  There’s a bit more to it than that but if you pick up a lens that has such a ring – do some research on how to use it and you’ll get a lot more of out of your small apertures.

If you’re curious what the little red dot means, that’s the infrared focusing mark. When shooting with infrared film you actually had to focus at a different place  than normal because the infrared spectrum of light is different than what we see with our eyes.  I used to shoot infrared film now and then, fun stuff, but tricky to handle, focus and you need to know what you’re doing with it.  There’s now ways to replicate fairly closely that same look digitally, even though now and again I think about shooting some film.

That’s it for lens numbers (I hope!) if I missed anything let me know.  Share a photo of your lens and any numbers you can’t decipher and if I don’t know what it means I can try and find out for you, or maybe someone else can help out in the comments section.

Read more from our Cameras & Equipment category

Darlene Hildebrandt is an educator who teaches aspiring amateurs and hobbyists how to improve their skills through articles on her site Digital Photo Mentor, online photography classes, and travel tours to exotic places like Peru (Aug 31st - Sept 13th, 2019), Thailand, and India (Oct 28th - Nov 11th, 2019). To help you at whatever level you're at she has two email mini-courses. Sign up for her free beginner OR portrait photography email mini-course here. Or get both, no charge!

Some Older Comments

  • BK August 23, 2013 07:47 am

    Thought so. I'm testing old Canon FL lenses on Lumix G1. Thanks so much for your help!

  • Darlene August 23, 2013 02:42 am

    @bk yes I think that is what happens with some film lenses. The newer lenses have a contact that communicates with the camera body about the aperture, while some older lenses do not have that. All the other settings are in the body but aperture is in the lens that's why only that setting is affected.

  • BK August 23, 2013 01:07 am

    No problem re: markings, but I do wonder if it is normal (because of 'shoot w/out lens' on) for the aperture (f stops) to not be recorded in the camera's display when reviewing photos in camera. Shutter speed, ISO, etc., is recorded. Just not aperture setting. Doing something wrong? Thanks!

  • Darlene Hildebrandt August 22, 2013 04:08 am

    @bk - can you show me a photo of the lens in question then maybe I can help you identify the markings

  • BK August 20, 2013 04:44 am

    Thank you, Darlene! As an 'older' photography student just learning, I can always count on your wonderfully detailed (but simple) explanations. Have some old Canon FL lenses to experiment with on Lumix EVIL and never having experienced film cameras I had trouble finding info about the scale markings, etc. Greatly appreciate your info--

  • Darlene August 2, 2013 02:57 am

    @1feistymama - frames per second and recovery has mostly to do with the camera body. Moving up from the SX40 to an SLR will help with those things. Where the lens numbers come in is how fast it focuses. Sometimes a lens with a larger maximum aperture will not focus as quickly, especially in the dark, as one with a larger aperture - so yes knowing what all that means is good information when shopping for new equipment.

  • 1feistymama August 1, 2013 08:17 am

    Thank you for the post. I've been reading a lot of articles on this site, trying to learn about dSLRs since I'm interested in upgrading from my SX40. I'm trying to determine whether or not I need to do so, and if I choose to upgrade, I would like to make an informed purchase. I would like something with more fps and faster recovery than the SX40 and I've heard that sometimes, it's the glass that makes the difference so understanding the numbers on the lens is something I think I need.

  • Darlene June 19, 2013 05:06 pm

    @photography by Sonja thank you that helps when good people appreciate what I do. As for the others, well . . .

    @Brandon you'll always pay more for the Brand name lenses versus the third party ones like Tamron and Sigma. They both make very good lenses also and are good choices. I suggest you read reviews on all the choices, go try them out at a camera store, and then decide.

    @merrilyn and Osilva thank you!

    @Steve good to know thanks

    @Ramneed no DOF is not affected by the exposure time

  • Kelly June 17, 2013 11:16 pm

    I love your site. You have answered already so many Q's. I'll be back when I can spend time perusing your many offerings. Thank you for sharing!

  • Ramneek kalra June 17, 2013 08:07 pm

    @Darlene, and @JVW, thanks a lot for your suggestions.

    I also found an android app that can tell DOF for many lenses and cameras, here is a link to it.
    Found the values from this app were fairly accurate.

    I wanted to ask one more thing: Does DOF change with longer exposure?

  • SMSabir June 16, 2013 08:19 pm

    @jvw I just want to say thank you very much for being so kind and generous in sharing T Stop information with me, honestly it gets very difficult for a newbie like me to learn about such stuff without attending proper school or having training.

    @Darlene I truly appreciate your kindness in helping people like to understand all this from basic level, please keep up the good work, thanks.

  • Darlene June 15, 2013 03:22 am

    @artoromm you can post that kind of off topic comment any time, I'm flattered, thank you so much.

  • ArturoMM June 15, 2013 03:12 am

    Darlene, you have so many admirers, I think is not just your technical expertise and the communication habilities, is also the respect you have even to your critics.

    This world needs more people like you.

    I apologize for may comment not being on the subject of the article.

  • Steve June 14, 2013 10:01 pm

    Good article.

    Older Nikon lenses do not need adapters.
    Even old film lenses will mount on the latest model cameras.

    Also, all of my Nikon lenses have an auto-focus that is designed to be used manually without changing any settings. It will not damage the lens. They are marked with "A/M" to indicate auto and manual focus in that setting.

  • Michael S June 14, 2013 09:51 pm

    I didn't know ANYTHING when I got my first dslr as a gift years ago, sites like this were very helpful. And now I can guarantee that the images I produce are as good or better than @Bill and @Jeryzkid. If you are new to photography, don't let the worthless words of these two folks get you down. I specifically remember when I learned how the aperture controls the image, from there on out photography has been a blast.

  • Darlene June 14, 2013 02:07 pm

    Awesome thanks for that!

  • osilva June 14, 2013 02:01 pm

    this is a very helpful article. I enjoy all your articles Darlene..they are helpful, to those, like me, who do find it confusing to read manuals, I rather see examples like you noted on this article. why people make sarcastic comments about these articles baffles me. thanks and keep the articles coming.

  • Merrilyn June 14, 2013 11:19 am

    Thank you Darlene. I really appreciated this article. Nothing like it in my camera manual, in which the print is so small that it is a hassle to read anything. We are not ALL experts and I look forward to all of your easy to understand articles.

  • JvW June 14, 2013 09:25 am


    To put it very simply, F-stops are calculated ratios, and T-stops are measured light hitting the film, Transmitted light.

    F-stop is calculated by dividing the focal length by the diameter of the front element: A 200mm f/4 lens would have a front lens of 50mm diameter. A 200mm f/2.8 lens has a front element of about 71mm. That's why those fast lenses are so big and heavy, lots of glass.

    All the lens groups in a lens, especially zoom lenses with lots of glass, absorb some light, so a little less than the calculated f-stop value hits the film/sensor. The more glass, the more loss. That's where the T-stop came into movie jargon. They measure the light hitting the film, Transmitted through the lens, and label the lens with that result. That way, when switching a T/4 50mm for a T/4 135mm, the amount of light Transmitted is exactly the same, so scenes with different lenses can be exposed the same.

    A T number, because of loss of light, is larger than the F number for a lens. For example, an f/2.8 could be t/2.9 or so.

    So yes, T-stop is more accurate than f-stops as far as light hitting the film is concerned, but the difference is not huge. It is important for film because switching lenses mid-scene could of course cause small but abrupt changes in lighting, something you probably would hardly notice with two photographs. So T-stop is more important while filming than for photos.

  • Brandon June 14, 2013 08:31 am

    Thank you for this article as I am also a beginner. I would like to ask when buying lenses why are some more expensive then others for example I have a Pentax k-x sale and found a tamron lens AF 70-300mm F/4-5.6 Di not bad for price but a similar lens for Canon or NIKON are a bit more pricey. Again thanks for the article.

  • Darlene June 14, 2013 07:08 am

    @smsabir - sorry I can't really comment as I'm not at all familiar with Cine lenses or doing video. Maybe someone else on here is knowledgable in that area?

    @Jason - yes good point. There is actually a Canon lens that goes 5:1 meaning 5x life size so you actually enlarge objects that are very tiny. It's an amazing lens.

  • Photography by sonja June 14, 2013 05:33 am

    It very sad that one person feels so against learning, even if it is review things we have learn in the past. I would like to say you choice to read the information on this website, you choice to to get the information delivered to your email address, if you think this information is beyond you maybe you should try another website, and leave the rest of us enjoying the wonderful information they send us.
    I appreciate all the information even if it is below my level of photography sometimes, cause you never know when something you read will give the OH YES moment. We all need to learn and sometimes a manual just doesn't do it, and I do recall the title of this website is DIGITAL PHOTOGRAPHY SCHOOL, so I would think we would learn the basics on this website.


    Thank you from the rest of the population that likes to learn.

  • Beginningrand June 14, 2013 04:34 am

    Just wanted to thank you for the clear information. I am a beginner in digital photography and just bought a camera for my husband and me to enjoy. I'm not especially fat, lazy or dumb, just inexperienced. I love the articles on this site, which I often read alongside my camera, tryng things out as I read. I sure other newbies like me find a lot of helpful information here. I thank you again for taking the time to help us all out.

  • Jason Sewell June 14, 2013 02:55 am

    Great information. On macro lenses, such as the Canon 180mm f/3.5L, you'll see another scale on the lens barrel indicating the image magnification size ratio. This is expressed as a ratio starting at 1:1 at the minimum focusing distance, and increasing to 1:10 around the 2 meter mark. This ratio represents that size of the image on the sensor, with 1:1 being "life sized" (true macro).

  • Avens June 14, 2013 02:21 am

    Thanks for the article. I am a beginner photographer, and am trying to research and learn before spending several hundred dollars on a camera (and more on lenses). Much appreciated.

  • SMSabir June 14, 2013 01:28 am

    Hello Darlene! A newbie to dslrs and super passionate about learning dslr cinematography. Read your artical and honestly loved it.

    I am really keen to buy a few Rokinon/Samyang CINE version lenses which have T Stops instead of F Stops. Some people say that T Stops are more accurate then F Stops.

    It would be really kind of yiu if you can shed some light on this.


  • Darlene Hildebrandt June 13, 2013 02:37 pm

    @jake - thanks for your support. We can note that person hasn't replied again. Seems they are in the minority. Indeed what does it matter how you learn, just that you learn!

  • Jake June 13, 2013 01:21 pm

    I am a new photographer and had some extra time so I wanted to start reading up on lenses and different types of cameras and I am a lil upset with the comments of some very ignorant people on here.This article was absolutely perfect for some light reading on a new subject. The guys who say "this is whats wrong with america obviously dont realize they are the friggen problem. WHY WOULD YOU DOWN SOMEONE FOR TRYING TO EDUCATE PEOPLE. Absolutely stupid and irritating. Whats wrong with this country ...well part of it is people who hate their lives so much that they feel the need to displace their unhappiness onto others in the form of a stupid comment in an attempt to down them when really they are just making themselves look absolutely foolish and ridiculous. IDIOTS.

  • Darlene June 13, 2013 07:41 am

    @miriam - that is exactly why I write this sort of thing, thank you for letting me know it's appreciated!

    @SS, Brenda and John - thanks for your comments!

  • John Godbey June 12, 2013 11:34 pm

    Good job Darlene explaining basic lens info. I agree that there are many avenues of education, one of which is one on one conversations with fellow photographers.

  • Brenda June 12, 2013 10:45 pm

    Thank you for your very clear concise explanation. I have read and listened to many people, none of which made it very user friendly. Thank you for simplifying it for us "dummies". I suspect I'll get more out of mt lenses now.

  • S S June 12, 2013 01:51 pm

    This is a good article.
    Just like big things have small beginnings. This article adds the comprehension in the manuals (given in the form of in-animated instructions) which is required by beginners at their start and is required by experts as a reference (sometimes, experts need verifications too).
    Thanks Darlene

  • Darlene Hildebrandt June 12, 2013 07:40 am

    @Ramneek it is nearly impossible to do a hyperfocal distance scale on a zoom lens because it will be different for each focal length. So you will only see this on fixed or prime lenses. Calculating on the fly, no not easily, sorry. Perhaps try this calculator but you have to plug in your lens focal length and is online. Not sure how to take it with you


    As JVW indicated in his link the DOF also depends on the camera body you are using. So pretty tough to calculate manually. More math than I want to do taking an image. :-)

    @Clay - re: autofocus yes true, thanks for mentioning that. So you need to check your lenses manual on what it says about AF and manual focus.

    re: the aperture number, it's not quite that simple it's not really a fraction but a ratio. From Wikipedia:

    "the f-number is the ratio of the lens's focal length to the diameter of the entrance pupil"

    So in a sense that is correct. A larger opening will give a larger ratio number. I tell my students to just remember this if they get confused. This is really simplified and dumbed down but it works for remembering I find.

    #1 - small number - big opening (inverse of what you think it should be)
    #2 - small number less depth of field, large number larger depth of field.

  • Clay Teague June 12, 2013 04:19 am


    Good information. One thing - some lenses are designed to allow manual focusing while in auto focus mode.

    Another interesting thing about aperture that a lot of beginners have trouble with:

    Why does the lower number let in more light?

    Because it is really a fraction. 2.8 is really 1/2.8 and 16 is really 1/16. If you remember fractions back in math class, 1/2 is larger than 1/16, thus the opening is larger and lets in more light.

  • JvW June 11, 2013 09:26 pm

    I forgot to mention that you won't find depth-of-field scales on zoom lenses like your Nikkor because DOF depends not only on aperture and distance but also on focal length. A simple scale can't cover all the possible focal lengths of a zoom.

  • JvW June 11, 2013 09:22 pm

    Hi Ramneek,
    Here's a link to a site where you can calculate DOF (depth of field) and hyperfocal distance for any camera, focal length and aperture and distance combination. On the left of the screen you'll find a link to where you can view/print tables, which I find a bit more informative (Online depth of field table).


  • Ramneek Kalra June 11, 2013 04:30 pm

    Could you please share the hyperfocal distance scale for 18-55, nikkor 3.5-5.6, kit lens.

    Also, is there a simple formula to calculate this distance on the run...

  • Cramer Imaging June 11, 2013 08:00 am

    Thanks, you just explained a feature on my fixed length 500 mm lens that I hadn't figured out yet: hyperfocal distance.

  • Miriam June 11, 2013 03:07 am

    Ms. Hildebrandt:

    I absolutely love the simple explanations and visuals on the lens descriptions. I feel so much better knowing that I am not the only one who has these questions! Quite a bit of the time, it is the "common knowledge" that is overlooked and not explained that halts newbies like me until we figure out the technical terms explained in the manual or can ask someone what it means.

    Thank you very much for sharing your knowledge!!!


  • Darlene June 11, 2013 01:51 am

    @Peter and Doug thank you

    @mark the aperture is actually a ratio so it's just expressing it as such. From this page on Nikon's web site

    "The f/stops are always indicated as fractions on the lens, by the way—that's why you always see them start with a 1, like 1:3.5-5.6. "


  • Darlene June 11, 2013 01:34 am

    @jeryskyd your words are harsh, not to me but to someone reading this and finding value, it's very insulting and not necessary here. If you don't find value in what I've written then I suggest you move on to the next article. Why do you both feel the need to add disparaging comments towards others? It's just not necessary, helpful, or called for.

    The truth? The truth is I've been doing this professionally for over 25 years and teaching for 3 years now. The truth is that camera and lens manuals are DRY and BORING and don't explain things well. Could one go buy a beginner photography book as you suggest? Sure. But consider this - they could also look for information on sites such as this! Both are valid options and I wish you'd stop discounting the way someone learns. Really what is the difference if they read the manual or read this article? It's still learning and information either way I don't see why you have both made a big issue out of it and made it about "the stupidity of society". What is society is smarter in that they know the manuals are dull and boring and they sought out other places for information?

    One must look at both sides of the discussion and be willing to see both. One can then agree to disagree but there is never a reason for name calling.

  • Jeryzkyd June 10, 2013 09:31 pm

    @bill, like it, true example of the Dumb Down Society Mentality... These are photography basics, if you dont know these things before you go out and buy a dslr then take a photoclass or read a book..@darlene my suggestion to someone who decides to read the manual, pick up the item you are reading the manual for and play along while you read, it might help you understand better... Dont get upset by the truth darlene...

  • Doug B. June 10, 2013 09:29 am

    I personally like articles like this, if for nothing else as a refresher on the photography art.

    I have a zoom lens, a prime lens without an aperture ring and several older manual lenses with aperture rings in my lens arsenal. This information is useful when I want to explain something to a friend just getting into photography and need some assistance. I just send them an article that explains things better than I could, then we discuss it.

    Thanks for posting.

  • Darlene Hildebrandt June 10, 2013 07:56 am

    @bill wow I'm sorry you feel that way. Some people choose to learn by reading online as their preference, I'm not sure why that makes one fat and lazy. I've also encountered many people who HAVE read the manual and it doesn't make sense to them because they are new to photography or digital and the terms are often not explained well in the manuals. So they look elsewhere for help.

    Each person also has a different way of learning. Some learn best in a group classroom setting, which for others is too intimidating or difficult for them to learn. Others learn best from books, or some from videos. Yet others learn best one on one from a teacher or tutor. Why criticize how someone different from yourself chooses to do their learning? If you get to the same end result what difference does it make?

    No need for name calling and statements of this nature. We are each different and if we can accept that we'll all get along better.

  • Bill June 10, 2013 06:02 am

    This is an appaling statement on the average American, and why our economy may be on the verge of a long term major decline. Have we become so fat dumb and happy that we go out, buy an expensive camera and don't see the need to read the manual, or go out and buy an inexpensive book on the fundamentals of photography?

  • Mark June 10, 2013 06:00 am

    What does the 1 on the left side of the colon for 1:1.8 mean?

  • Peter June 10, 2013 05:21 am

    Great article!! I really needed to know about the hyper focal distance