Photographic Lenses
Written by: Digital PhotographyPhotography Lesson #3
Since optical designs of photographic lenses (wide angle to telephoto) differ so radically we will not go into detail about optics. This lesson will cover a basic discussion of lenses and some good tips on lens use and care. Lenses are designed to refract (bend) light rays. Here is a basic convex lens (crude drawing below). Notice that this bends the light towards the center of the film plane. A magnifying glass is a basic convex lens.
A concave lens bends the light away from the center. In modern camera lenses, you will find a variety of these lenses with some individual elements oddly shaped. 
Below is a cutaway illustration of a typical camera lens. Notice the different shapes of the elements. The science of optical design has become quite sophisticated and as it has progressed we, the photographers, have benefited with sharper, faster, lenses with greater color purity.
Depth of field is a term we use in dealing with the sharpness of objects in our field of view. We know the subject we focused on will be sharp, but what about objects in front of, and behind? We control the sharpness of those objects by using THE APERTURE which is built inside each lens.
The aperture is used primarily for controlling the exposure (the lesson on Exposure follows this page, be patient) but it also controls the depth of field (depth of sharpness would have been a better term). Words cannot explain this as well as visuals so take a look below at how different aperture settings can control the sharpness of objects in front of, and behind, the subject you are focusing on:
I like to think of the aperture as a hose and how far the hose will reach if it is covered or not. If the lens aperture is “wide open” ,like a hose that you don’t cover the end at all, the depth of field is very shallow or the hose doesn’t spray very far… notice how the runner (below) is sharp and the other players are out of focus. However, if you close the aperture all the way down, or cover the end of the hose so the water can only escape through a small hole, objects in front of, and behind, will appear much sharper (see below). 
By keeping the aperture wide open (left) we give the runner a “3D” look. He stands out among the out-of-focus players and our eye is drawn to him. If we close the aperture down (right) more objects are in focus and the runner gets lost in the crowd. 
Therefore, if you have a camera that offers Manual Control, use “depth of field” to help draw attention to the objects you consider important. Now to some other tips lenses … TIPS ON LENSES: We always use a UV filter in front of the lens (instead of bothering with lens caps). The filter protects the lens and blocks out unwanted, hazy UV light. The glass used in photo lenses is covered with a coating (to correct some color problems) therefore, you should be very careful when cleaning the lens. We suggest that you not use lens cleaning fluids, rather a gentle blowing (your breath has moisture) followed by a gentle wiping with a clean, soft cloth or lint-free napkin. If the lens is seriously smudged then put a drop of lens cleaning fluid on the cloth and gently wipe. DO NOT apply lens cleaning fluid directly onto the lens… the fluid could get into the edges and destroy the adhesive that keeps the element attached to the barrel. Don’t bring a lens in from extreme cold … the moisture inside will instantly freeze up the whole lens. It is best to carry the camera under your winter coat when not in use. When making photos you should make sure the lens is in the palm of your hand, freeing up the fingers to focus. This takes the pressure of the lens mount AND provides for more steadiness. When using a telephoto lens you should also tuck your elbow into your side … which offers you more camera support (i.e., less shake). 
When carrying the camera on your shoulder (using the strap) the lens should point inward to protect the glass and keep it from banging into other things … like little people. You’ll find that the camera is now positioned in such a way that when you reach for it, it will go into your hand easier and feel more natural. 
FILTERS: There are numerous filters out there, some designed to correct color/light problems … others add special effects. We will discuss three basic filters (which you probably should have). UV/HAZE filter: It cuts out ultra-violet light rays. Although invisible to the naked eye, ultra-violet rays give bluish tint and haziness in color photographs. UV/HAZE filters make the picture clearer. This filter does not block enough light to cause you to make an exposure compensation, therefore it is should be kept on the lens at all times to protect the lens surface. POLARIZING filter: This filter subdues undesired reflections from non-metallic surfaces such as water, windows, etc. When used in color photography it will darken blue sky by blocking atmospheric haze. By eliminating that haze skies will be bluer, red objects will be redder …. in fact all colors will be much more saturated and true. CLOSEUP filters: These are simple lenses that, when attached to the front of your lens, will allow you to focus much closer … allowing you to make full-frame images of very small objects. The more powerful the closeup filter, the more you will have to “open up” the lens, because these filters do “absorb” some of the light rays. The filter should come with instructions that will tell you how much exposure compensation you should make. If not, simply experiment … AND take notes. Next we need to look at EXPOSURE CONTROL.
After all these years of feeling really confused and not understanding what aperture is, I feel very enlightened and confident now!
Thanks!
i agree with Tisha, thanks. ( seem to be saying that every section)The phrase “depth of sharpness” made everything come into focus. Also appreciated the explanation on filters.
Can you put a UV/Haze filter and a polarizing one on the camera at the same time? Would you even want to?
You can stack filters, and use multiple filters at a time. It all depends on the effect your trying to achieve. One reason to stack filters would be to take a picture of a fountain on a sunny day, restricting the light coming into the camera and allowing you to use a slower shutter speed for a more interesting photo.
I am amazed how much I have learned already. Easy to understand. Fantastic!
[...] covers things like, A Photography 101, Digital cameras, Lenses, Understanding Light, etc. then, once you’ve got the basics under-your-belt, they also have [...]
i am very impressed with your site,very informative.
I am feeling grateful with what i’m beginning to learn from your website. Thank you!!
Great help, this site is amazing !!!
this lesson really “taught me alot”
these are the strong basics which are badly needed because
if the foundation is strong building never collapse
I very much enjoy all the visual aids you include. They are that much more helpful in understanding the material. I’m a new member and a beginning photographer, but I’m really enjoying the site so far! Best one I’ve found!
these lessons are really informative and seem simple especially with tha visual things….great job…..i am really glad i found this one…thanks!
I just discovered this website and I’m amazed, I’ve been taking some good pictures that my friends find really amazing on facebook (they even ask if I am a pro photographer lol, but honestly I think I was blessed that my pics come out nice without even know what I’m doing, my best teacher was always the try and error thing but now I know what aperture means and I have taken some test photos and I am so happy…….. I am ready for more….. THANK YOU
Learning alot. and everything seems to be making more sense now.
Thank you.
After reading this section I have decided to buy at least a UV/haze filter and maybe a polorized filter, but am overwhelmed with options. can you give some input on size/brand? Will the “cheaper” brand give me the same results and will they work on my canon lens?
Nicole, each lens has a diameter in mm. If it is the right size it will work on your canon. For filters it typically makes littler difference what price you pay. One of the reasons we like Amazon is because they give customer ratings so you know the value of the product you are buying. Just search for the filter you’re looking for with the diameter in mm’s and you’ll find what you’re looking for.
I have a small digital camera. I bought it for like $80 at Walgreens. Does it come with these “lenses” built in? I’m so confused about this. Was I supposed to go out and buy one of the expensive cameras?
You only need lenses for SLR Cameras
Love the courses..for us beginners..it does explain things very easily for us. Thanks so much.
Courses are great… I’ve just bought a digital camera but I don’t think it’s a good one (costs $200), it’s a Samsung with a Samsung lens (18.6mm) My questions are:
How much can I do with that camera?
How important are mm in the lens quality?
Is it possible to use any filter with the camera?
Anyway, my grandmother has an old russian very good camera with a big lens (I will ask for information about it in the future)… But I’d like to know how useful my new cheap camera is.
Thank you!!
Camilo,
We’d have to the model of your camera to tell you more about lenses compatible with it. We can tell you that you can create great photographs with just about any camera. Don’t believe us? Check out our new article on Holga Cameras and Lomography.
So if you were taking a picture of someone outside say at a garden with water falls or fountains you would stack the uv filter and the polarized filter at the same time? What effect would that have on your photo?
UV filters reduce the haze and the fogginess of outdoor light, however their most common use is as a protection for lenses because their effect is undetectable in most situations. By putting a UV filter on your lens, it takes the scratches and little bumps, so if you need to replace it, you are replacing a $10 filter and not a several hundred dollar lens.
The Polarizing filters effects are much more stark. As you know, when you put on a pair of sunglasses that have polarizing lenses, everything becomes clearer and cleaner because the light that is bouncing off the shiny things is removed. Polarizing filters are most useful when photographing snow, water, bright sunlight, etc. Be aware that when you use a polarizing filter you are reducing the light to your sensor/film and increasing the contrast, so you might have to adjust if you don’t have enough light.
So, yes, you can stack a UV filter on a polarizing filter for photographing water. The both have different effects on the image, and both are helpful in reducing the glare and light bounce when you are photographing highly reflective subjects. The result should give you more detail in your image and less “hot” (overexposed) spots. Just leave your UV filter on all the time to protect your lens.
recently i bought a canon powershot g10. i believe extra lenses can be added to it.. if yes then how would it improve the picture quality.. is it needed?
thank u for the great course for beginners. i started today and already feeling enlightened.
Mini, you’ve got a special camera that is not 100% point and shoot and not 100% DSLR. Canon has some accessories and filters that will work specifically with this camera. I wouldn’t say they will prove the picture quality but they will expand the capabilities of the camera by using accessories such as the tele converter or Conversion Lens Adapter. Filters will be just like the one’s described here, only sized for your camera.
WOw this is so helpful. NOw i know what a polorized filter is.. wished i knew about it earlier because i took a picture from my hotel room and all it did was bouce back from the window and i saw my reflection in it.. i even tried it with the flash off and that didnt work either.. Really good to know.. Thanks!
This website is FABULOUS! I finally have a clarity on what aperture is and the purpose of different filters. I started with lesson 1 and will continue until the end. Thanks for such great and FREE information!
It would be good to know what is meant by f2.8 or f8. Right now, I only understand that smaller the number , larger the aperture or the camera opening , which lets in the light.
Also, physically why is it that there is less depth of field when aperture is larger?
Thank you !
Very Good questions, in fact we had to make two new articles just for you to answer them: fnumbers and physics of depth of field
nothing as good as this experience am having on your site..trust me am going to learn more all the way..thanks a lot.
How will I know what lens I need to take photo?
You use the lens that fits you’re needs. If you want to get close to the action use a telephoto lens with a focal length of 200 or so. If you want a fish eye lens you use a fish get a lens with a much smaller focal length. Zoom Lenses are always helpful as you can quickly change the focal length.
I have gotten through this stage of the course. A great course especially to pass time in Iraq. I have a 18-55mm lens and was looking for the filters that you suggested (UV, Polarized), I found some on amazon however they had one for an 18mm and another for the 55mm. Which one should I get to cover the ranges of my lens? I mostly shoot Landscape photos and family photos.
Chris, You’re going to want to look at the diameter of the lens, the 18-55 are just the focal lengths for you zoom lens.
I have a Nikon D40X and I have been asked to do some hotel room photography for their website. Problem is the rooms are very tiny, these are just old hotels that have been recently renovated, and I can’t get enough of the room in the shot. I currently have the 55-200mm 1:4-5.6G ED lens. I don’t know much about lenses at all. Can you please tell me what lens I will need to do this job.
I wide angle lens would work well. Here is an example of a lens you could get. It might be good to just rent one if you don’t plan on doing these types of shots often. Your just looking for a lens with a focal length between 12 and 50 mm.
Thank you so much for this site. I’ve always loved taking photos but just recently purchased my first SLR in May of this year. I have no desire to make photography anything more than a hobby but I’ve always been a ‘point & shoot’ kind of gal. I want to learn more so I can correct the errors that I’m currently having. ‘Guessing’ how things operate is no longer working.
Thanks again!
WoW! I am still a beginner photographer, I’ve owned a Nikon D40x, D80 and just purchased a D300s, which unlike the first two does not have an automatic mode, I still mostly photograph with the D80 in Auto mode but your site is the first I have found to speak in simplistic terms, I actually have a better understand of what Aperture is now! Thank you so much! I hope to be able to use my D300s more often as I go along this course and am able to apply what I’m learning!
this site has cleared up some questions I had. I have a Canon Rebel SX with a 18-55 zoom lens focusing care F stop and ISO speed. I’m trying to understand so I’m at this site to get the basics to get started again now back to trying this camera
THANK YOU!!!
I now understand!! the photography classes i’ve taken in the past NEVER went over ANY of this!!! go figure i was lost! but now i’m found thanks to you!!!! 8)
Thanks for the explanation of what the “f-numbers” are for. I have an OLD Pentax SLR, and I thought the only thing that the numbers were for was to limit the amount of light that came in – if it was bright, you went to the higher numbers so the picture wasn’t “white.”
But to learn now that it’s actual function is for depth of field…WOW!
Looking forward to continuing on…
again great lesson, ready for more!!
Wow!! Thanks for the site. I just received a Rebel T2i for christmas and have never had anything other than a “point and shoot” type. After five minutes with the camera, I was dissappointed and overwhelmed, thinking I would never be able to understand the camera at all. Your lessons have been clear and concise enough for me to follow. I am now looking forward to taking pictures and making lists for all the “goodies” I need to go with my new toy! Thanks so much!!
Thanks so much for explaining the whole filter thing. I do have a UV filter. Not that I truly understood why, not I do. Next I do want to get the polarizing filter. Can you put them both on and does it matter about the order or is that even an option?
With all the processing you can do afterwords filters have become more for protection purposes mostly. I haven’t ever seen stackable filters.
Thanks for giving us information about lenses ..
I really had new information about it and useful one.
but I hope you give us specific information about specific cameras.
like canon SX30..
I just bought a close up filter from HOYA for my zoom lens 18-55 mm SONY ALPHA. When i mount it on the lens , both auto& manual focus does not work.I wonder if i can use the filter on a fixed focal lens instead of a zoom lens. Please give me advice about this matter. Thank you very much.
If you install a close up filter it could be that combined with the particular lens the camera just can’t focus. It’s probably moving back and forth desperately trying to. You’ll want to make sure your camera is set to macro so that it can plan on things being very close. I’d have to see what you were doing to really know how to help you.
I’ve bought a polarization filter (Hoya), but I don’t see much difference… I see pictures on the internet in which you just look through the filter and twist it and see a lot of change. I only see a tiny bit of difference when looking at a really shiny object. Maybe I have to wait for better weather, with lots of sunshine and blue skies?
Polarization filters are mostly just used to protect your lens. The technology is also used in sunglasses and reduces glare, but the polarization filter won’t dim light like your sunglasses, it will remove haze and make skies clearer. It could also be that your auto white balance settings on the camera are minimizing the effects of the filter. If you switch to daylight white balance, you should see more of an effect.
Regarding the three filters you recommend we must have, especially the UV Haze filter to protect the lens. Will the use of any one of these filters not be recommended indoors under artificial lighting, or could the UV Haze filter be used indoors and outdoors?
Thank you.
A UV Haze filter wouldn’t be necessary indoors. It would just block a small amount of light, so it would be hurting more than helping indoors with artificial lighting.
Thank you, thank you, thank you. I just spent a weekend in a National Geographic Photo Workshop that was basically go and shoot and then get critiqued. Very little technical information. Your lessons are much better. Wish I had seen them before I sent a check to Nat Geo.
This site is great. I’m just getting back into photography after a few years away and this site is helping a lot. It helps refresh and clarify info I knew but either forgot or had trouble getting straight in my head in the first place.
Great site so far, look forward to learning more!
Thanks,
I am so glad I found this website. It has been very helpful.
Thank you,
Very informative, good presentation…….especially for a complete novice like myself.
Great Site for a refresher. I’m just got my first DSLR, but not my first SLR, I’m
moving up from a Minolta XD11 35 mm, to a Sony Alpha A55. I want to find an adapter so I can use my Vivitar Series 1 70-210 f2.8 MD mount. I know it wont auto focus but I should be able to use it as a manual focus lens, hopefully in manual and Aperture and shutter priority modes.
Thanks
This is great, I am so glad I found your website. I am learning alot. Thank you so much for making this website available..I can’t wait to see what I will turn out in images, once I have completed the lessons. Again thank you!
It sounds like you were saying lenses come with a UV filter nowadays? If they do, is that why my pictures are so blurry? I used to clean my lens now and again with cleaning fluid– did that remove some of the filter? Or is the filter a separate thing that you put on top of the lens? And if so, what is my problem in the dirtiness of my pictures? I’ve cleaned it the right way, and it’s still smudgy.
@janae The filters don’t come with camera’s, and digital cameras don’t really need UV filters. The filters are sold for the purpose of protecting the lens you purchased. They are a transparent lens cap. If you are careful with your lenses you don’t really need them for protection and they just get in the way of you and your subject.
So from what I understand, filters for digital cameras are only for effect?? Learning a lot from these lessons.
@davepostman Filters are for adjusting the optics. You can call them effects, but in the case of a haze filter it can cut through the haze, making for a clear picture. So I wouldn’t write filters off as “only for effect”.
Thank you for the invaluable information so far. Easy to follow, easy to understand . I felt I had to comment at this early stage. Took me 3 minutes to totally understand aperture and what the adjustments do. Taking AS photography , 2 year course , started 2 months ago . Many thanks . Guess you will hear from me again.
Are the UV/Haze and Polarizing filters only for SLRs? Or can they be bought for point and shoots (nikon coolpix L120)?
Thanks for the tip with the cleaning fluid. I used to spray it directly onto the lense. Hope I have not yet damaged it
Awesome knowledge sharing and that also at no cost !! Thanks for these wonderful lessons..
This Course is simply AMAZING!!!! I love it I wanted to start lessons but I couldn’t do to work schedule but this photography course is very helpful I don’t feel like I am a complete ignorant, I bought a Canon EOS REBEL T3 – EOS 1100 D and I would like to know if it comes with filters and if it doesn’t wich ones would you recommend?
Unfortunately the camera companies keep as little as possible in the box. When picking a filter you mostly just need to make sure it’s the right size to fit on you’re lens. In you’re case you’ll be looking for 58mm filters.
I recently purchased a Nikon coolpix P300 and it has a lot of features I’m not familiar with but it’s far from the DSLR’s most folks here mention. Will I be able to progress in your course without a better camera?
Although the Nikon Coolpix P300 isn’t a digital SLR it still allows you to set the Aperture, set shutter speed & ISO and has a Mode dial like digital SLR’s that allow you to use shutter priority mode and aperture priority mode.
when photographing insects is it helpful to use a close up filter? I am shooting with a Nikon D300s and still trying to learn everything after moving up from a Nikon D40. And thanks for all the great info I feel as though Im going to be getting alot from these courses!
Using a close up filer to shoot macro photography is an easy alternative to getting a primary lens just for those close up macro shots. They’re eventually a magnifying glass at the end of your lens. Just don’t go burning ants with your close up filter
Wow, after a solid year of practicing and playing around with settings to get the desired picture I’ve wanted…in 30mins on this site, I’m finally on my way. Just about everything i’ve previously read; I’ve read here, but what I’ve read here has the clarity of terminology with illustrations; that has made all the difference. It was like trying to learn the english language without the vowels; then you gave me the vowels. Thanks a million.
According to my friends I’m a natural, but there is more to just taking a pretty picture and this site is giving me a better understanding not only how to take an awesome shot, but more about my camera. Helping me achieve my goal in honing my skills
awesome page!
I want to get the UV filter and the Polorizing filter but I don’t know what I need. I have 2 lenses that came with my Nikon camera. One is a 18mm-55mm and the other is 55mm-200mm. Is there just one filter of each type that will work with each of these lenses?
I love this site!! I am just learning photography, and this is very helpful.
i have a opteka babydeath lens for $200 it sucks
Hello,
Love this site, it provided me enough knowledge to talk about photography. I started reading all the topics and decided to get a DSLR for my self and start my new hobby. I was wonderign what are the essential lenses needed for a beginner like me and can you explain me what is the difference between 70-200mm and 35-200mm ?
Thank you,
Hemanth Kolla
With each you’ll be able to “zoom in” the same amount. With a 35-200mm you’ll be able to zoom out more and have what you would call a “normal” zoom. 70mm is still telephoto so you’ll have a lot more choices of how to frame a shot with a 35-200mm.
I have a canon t2i and purchased the lensebaby lenses.Do you have you any thoughts that might be helpful seen it as away to play more with setting up the camera instead work with the preset.
wow. thanks so much. what a wonderful site you have given to us. For a time i was so confused about photography i didn’t even know what to ask or who. your style is so easy to understand. give yourself a really big pat on the back. thank you.
Thank you for this valuable information. I have learned a lot I didn’t know. Very easy to understand.
Great tutorials, I am hooked! Very new in photogoraphy, and can’t wait to improve my skills after reading more of your lessons!
I didn’t know what aperture is and how it makes differentce, it is so helpful I found your website
THANK YOU!
I have been a Professional for over 17 years, and this website is still helping me to rebuff and reacquaint myself with things I have forgotten over the years. I love how you have the images to help make everything more understandable! You guys are great!
I am not a professional photographer I just have a kodak easyshare C1550 and these lessons so far have helped me so much! Especially the lesson on Exsposure. I enjoy taking alot of nature photos and when I was taking pictures of yellow flowers it wasnt well defined – the yellow mixed together and you couldnt tell what you are looking at. Right after I read that lesson I hurried outside to try again after adjusting my IOS and Exposure. It worked! Thank you so much for these lessons!
Great website! I am learning so much! Thank you for teaching us free of charge!
I just wanted to THANK YOU for sharing your knowledge with us on your website and for doing so in such a philantropic way. I am totally new to photography and I was a bit scared of the terminology but you has made it so easy to understand that I am learning a lot. You are a great teacher and a noble person!
Thanks again!
Love the site, it is teaching me so much. I have just been bought a Fuji Finepix S4400. Can filters be attached to the lens? Also would there be 1 thing you would purchase to get the most from this camera?
Thank you loads…i finally have a clear understanding of the f stops.
Ah, the mystery of the f-stop, has been made clear, and what it really does, simply amazing that the gordian knot of photography is slowly, and so wonderfully being untangled. Looking forward to more wonderment. Thank you
I am really enjoying those lessons. They are helping understanding some of the essntials in photography. Thank you.
i am really happy i’m learning so much so fast. But aren’t lens caps protective enough? Some photographers use them. I am yet to buy a camera which would u recomend for a beginner like me?
Very good one. You have the deep knowledge and teaching abilities.
very useful for the beginners. Thanks to your efforts.
Thanks so much for your time and effort to teach people, most grateful. Please can you recommend any camera for me? I am a beginner.
I am a beginner with a Canon EOS Rebel T4i. I am enjoying your on line course very much. I would like to get a telephoto or macro lens mainly for some portrait shooting and perhaps some landscape. I do not want to spend a ton of money until I get the hang of it all. Is there a lens that you can suggest? I know someone selling a canon EF 75 300 f/4-5.6 for 100.00 new…but I have read some ” not so good” comments on this lens….I would love your suggestions. Thanks so much!!