What is DSLR Crop Factor, Depth Of Field, Lens Image Circle – Filmmaking Tutorial

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DOF, crop factor, and lens types

The first thing to understand is that lenses are built to project a certain size image circle, a full frame lens, also known as a 35mm, projects a 35mm size image circle. Then we have cropped sensor lenses, which are referred to as digital only, or digi, or whatever horrid marketing terms they chose, and basically they are built to project a smaller image circle, because the cameras they are intended for have the smaller sized ‘cropped’ sensors.

Likewise a 4/3rds sensor camera has 4/3rds lenses, and 16mm and 2/3″ sensor sized cameras have lenses with 16mm sized image circles. You can usually put a larger format lens on a smaller format camera, but it won’t see as much of the image circle, which is what we call a crop factor. you cannot go the other way, because then you will get a peep hole effect, vignetting to the extreme.

And now for our first debunk, because every time i hear someone talking about dslr video they say, well, the 5d has the amazing shallow depth of field, and it’s because of it’s huge sensor. Now granted, i’m sure not everyone out there thinks that sensors create DOF, but we’ll clarify it for those who may not know: consider this demonstration, you can put a 35mm type lens on either a 35mm full frame camera, or on a smaller sensor body, but that sensor is going to ‘crop’ that larger image circle, so we’re going to see a narrower FOV. So imagine this same lens on either camer, one with the larger sensor, one with the smaller.

So where did the dof change? Here’s a clue, it didn’t. the sensor has nothing to do with DOF, it is physically impossible for the sensor the create or manipulate DOF, it simply captures the light being projected onto it. DOF is created in the lens.

Moving on, in practice you can end up with shallower DOF with a larger sensor because the sensor is seeing more, aka larger field of view than a smaller sensor, so to get the same field of view as a smaller sensor camera you will need a longer focal length, and that in turn leads to a shallower depth of field.

One last thing on DOF, many of you at one point were shooting something and said to yourself, hey, i want a shallower depth of field, let me pull back the camera and zoom in, because a longer focal length gives me a shallower depth of field. Well, yes, but no, not for what you just did.

Try this out for yourself: Take two different photos of the same scene, place an object or person out in front of a background. Use a 50mm focal length. Then take the second shot by moving the camera back far enough so that you need a 100mm focal length to maintain the same field of view of that object/person. Change no other settings, especially keep the aperture the same.

You’re probably now looking at the two photos and calling me an idiot, because of coarse you’re seeing much more background blur in the 100mm shot. Actually… you’re not. What you’re seeing is the exact same amount of blur.

The reason the DOF stays the same is because you didn’t just use a longer focal length, you also changed the focus distance, there is an inverse relationship between the focal length and the distance of the focus subject, what you are actually doing by pulling back is simply magnifying the background bokeh, and anytime you magnify an object, you see more detail, and in this case you see more blurry detail. To your credit, it is achieving what you were out to get, a blurrier background, but when going about it or showing someone how to do it, be sure to not pass along misinformation by saying your creating a shallower depth of field. Your actors have exactly the same amount of space to move in.

Lastly, I want to put something in it’s place: Full frame sensors will not make you famous. See because ever since the 5D2 came out, people have been clamoring over the Full Frame “look”, and I hear far too often about how smaller sensors are garbage. Well those who say such things are children, children who need to learn…

The good old 16mm sized 2/3″ sensor. Which, was the first sized sensor to be used as the A camera on a hollywood production, which was star wars episode 2 shot on the f900. So riddle me this filmmaker, you’re saying that you need a FF, when your ultimate competitor is doing just fine with a fraction of that size… i call BS. Case in point, nearly any modern sensor size over 1/2″ (EX1) will give you a great image.

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  • OH MY GAWD!!!! Thank you for doing this video!! I was wondering if you could do another video with 2 lenses with the same mount, but with different image circles, using the same example's of sensor sizes.

    let's say I have a ASP-C lens (canon mount), and a Full Frame lens (canon mount). The image circles will be different sizes correct? Because If I use a FF lens on a ASP-C sensor, I will get a crop factor, and if I use a ASP-C lens on a FF sensor I will get vignetting.

    If I'm not mistaken the distance from the lens mounting face to the sensor on ALL Canon camera's are the same distance. Correct?

    Patrick Fougére June 2, 2020 10:41 pm Reply
  • An amazing guide which gave me the ability to turn myself from an amateur photographer to a near professional, I found the quality of my pictures and videos dramatically enhance after reading this guide, a definite help to anyone who wants to learn how to take more breath taking stunning photographs. https://plus.google.com/b/117576921052578751760/117576921052578751760/posts/Fk3sfQJu8AY

    Benjamin S. Valdez June 2, 2020 10:41 pm Reply
  • You are wrong on the fact that the sensor has nothing to do with the depth of field. It has an effect but it is opposite what people think. Smaller sensors have less depth of field as the image is magnified more. If you then reduce the focal length things turn the other way around.

    Okaro X June 2, 2020 10:41 pm Reply
  • Excellent. Clear understanding of the facts!

    Gil Gillis June 2, 2020 10:41 pm Reply
  • Good Zinger!

    TheLivingDeadOne June 2, 2020 10:41 pm Reply
  • both the lens and the sensor effect the dof,the lager the opening(lens)the more light can stray/miss the sensor and give you less in focus,but having the smaller sensor means even thought the light is stray it is not being collected by the sensor.A simpler way of saying this is your not using all of the lens so it is harder to get a smaller dof.

    M.C. Grigg June 2, 2020 10:41 pm Reply
  • Thank you sharing .

    benjamin wright June 2, 2020 10:41 pm Reply
  • I hate when people yell at me when someone even asks my a question with my film-writing.

    SAMURAI: MEDIA MAINFRAME GLOBAL June 2, 2020 10:41 pm Reply
  • That was awesome, because it was so precice and true

    Video1 June 2, 2020 10:41 pm Reply
  • Thanks for sharing

    LIFE PAST107 YEARS ON EARTH June 2, 2020 10:41 pm Reply
  • Very well put!

    XEPHULA Social Media June 2, 2020 10:41 pm Reply
  • Wow, great vid and your closing is what every filmmaker needs to hear. It's not the camera, its the person behind it. People forget that once upon a time movies were made on Super8. Nobody complained because for the most part the directors and writers had a good story to show with it. Bravo sir.

    Sylvester Folks June 2, 2020 10:41 pm Reply
  • it may physically connect, but it will look like you're looking through a peep hole. some lenses actually will even work if zoomed in enough, like the tokina 11-16mm is an ef-s lens, but it happens to work on full frame at the 15-16mm zoom. some full frame cameras now also have a setting to be able to crop to these lenses

    A. Film Group June 2, 2020 10:41 pm Reply
  • if I purchase a Full Frame Digital Camera and have EF-S lenses… will something weird happen? I am little lost with this topic , thanks

    Bernardo A June 2, 2020 10:41 pm Reply
  • So very true, it's all in the preparation and then the successful execution

    Andrew Lewis June 2, 2020 10:41 pm Reply
  • I love how you emphasize the importance of pre production. Many people don't know how important that part of filmmaking is.

    Lloyd K. Hembrador June 2, 2020 10:41 pm Reply
  • Camera does not make the photographer/Filmer

    Pablo Aguilar June 2, 2020 10:41 pm Reply
  • Great Video, thanks 🙂

    Radoslav Yordanov June 2, 2020 10:41 pm Reply
  • If they're making Star Wars prequels, they're not doing better.

    Carl Siemens June 2, 2020 10:41 pm Reply
  • Thank you so much! This cleared up a lot!

    theredsaptree June 2, 2020 10:41 pm Reply
  • That was really helpful thanks

    Phiniox Glade June 2, 2020 10:41 pm Reply
  • @tamim4ever A full frame sensor will give you a stop in all ISO's less noise, but having a crop sensor under 800ISO you should be fine i think.

    lightmanfilms June 2, 2020 10:41 pm Reply
  • @tamim4ever You are welcome, and also would have been great if mediahaloTV is a well informed filmaker and should also explain to some people the difference of DOF from the Bokeh effect which i heard that some people don't know the difference…

    lightmanfilms June 2, 2020 10:41 pm Reply
  • @lightmanfilms thanks 🙂

    Tamim Aflah June 2, 2020 10:41 pm Reply
  • @tamim4ever Yes it is correct.

    lightmanfilms June 2, 2020 10:41 pm Reply
  • I heard that full frame has less noise than cropped one, is that right ?! :

    Tamim Aflah June 2, 2020 10:41 pm Reply
  • you are very thorough. I learnt so much..still learning. love the last bit about the camera. Well said…Im subscribing

    jamradikal June 2, 2020 10:41 pm Reply
  • Awesome, thank you !!!

    Anca Boieru June 2, 2020 10:41 pm Reply
  • great explanation

    Sam Vickvicki June 2, 2020 10:41 pm Reply
  • #win

    Mohammed Zainal June 2, 2020 10:41 pm Reply
  • Fantastic, the humble newb appreciates any and all info regarding DSLR video! Question for you sir.. What are a couple lenses that are commonly used for DSLR filmmaking, and why?

    Dallas Bagley June 2, 2020 10:41 pm Reply
  • ashdjfksahdfkhakf
    Translation: I feel smarter now :3

    DynastyOfWhatnots June 2, 2020 10:41 pm Reply
  • I'm still confused about the def of crop factor but thx for the info. I think by def a 85mm on the 5D is = to a 50mm on a Super35 or is it the other way @? Thx…and hooray for skill and scripts over cams…I dj'd with $100 turntables and killed all the guys with the $400 ones back in the day…;-) cheers

    fromthebottom2thetop June 2, 2020 10:41 pm Reply
  • Great video, and I Iove the ranting.

    Shawn P. Boyle June 2, 2020 10:41 pm Reply
  • Very good explanation. I love your style. Not even 500 views!!!.. This simply tells that many guys just want to do magic with their camera without knowing the basics.

    007emperor June 2, 2020 10:41 pm Reply
  • AWEsome, simple explanation both visually and verbally. And very sensible take/advice on the film shooting aspects toward the end. Great job, hats off to ya!!

    neipas13 June 2, 2020 10:41 pm Reply
  • @mediahaloTV Excellent. From one filmmaker to another, I say? Keep up the good work!

    Michael James Jordan June 2, 2020 10:41 pm Reply
  • @Katana2040 My pleasure! if there are other things you would like to see clarified/gone over, do let me know, i'll be doing lots more of these

    Darren Levine June 2, 2020 10:41 pm Reply
  • FINALLY someone understands the correct meaning of 'crop-factor'. Well done, sir!

    Michael James Jordan June 2, 2020 10:41 pm Reply

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