Dispelling myths on sensor size, crop factor, and depth of field

Mar 30, 2017

John Aldred

John Aldred is a photographer with over 20 years of experience in the portrait and commercial worlds. He is based in Scotland and has been an early adopter – and occasional beta tester – of almost every digital imaging technology in that time. As well as his creative visual work, John uses 3D printing, electronics and programming to create his own photography and filmmaking tools and consults for a number of brands across the industry.

Dispelling myths on sensor size, crop factor, and depth of field

Mar 30, 2017

John Aldred

John Aldred is a photographer with over 20 years of experience in the portrait and commercial worlds. He is based in Scotland and has been an early adopter – and occasional beta tester – of almost every digital imaging technology in that time. As well as his creative visual work, John uses 3D printing, electronics and programming to create his own photography and filmmaking tools and consults for a number of brands across the industry.

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Nikon & Canon crop cameras have been out for over 15 years now. But different sized frames isn’t new to digital. Even back in the film days, we had 110, 126, 35mm, half a dozen sizes for medium format, and a few for large format. It still always amazes me how much the concept of capture size still confuses some people.

This video from photographer & YouTuber Blake Evans (aka biscuitsalive) hopes to dispel some of those myths and clear up the confusion. It does goes very in-depth into all the ins and outs of sensor size, focal length & field of view, as well as aperture & depth of field. So it may have you asking more questions than it answers!

YouTube video

Blake’s video doesn’t actually show any new information. It’s all been out there on the web before, but this is a good explanation of many of the principles all in one video. The video goes through some of the basic principles of how lenses, focus and depth of field work, and then how it all relates to sensor size.

He also shows some side-by-side comparison to illustrate just how you can achieve similar results on different cameras with differently sized sensors.

For me, personally, the trick to figuring everything out has always just been to approach it in a different way. I don’t care about the sensor size, and I don’t look at the focal length of a lens first, I look at its field of view relative to the size of the sensor I’m using.

Whether it’s Micro Four Thirds, 1.5x Nikon crop, 1.6x Canon crop, so-called “full frame” or one of the several sizes of medium format sensors, a given focal length will offer a different field of view on them all. So, why think in terms of focal length? I look at my scene, and say to myself “Ok, this is what I want on the left side of the shot, and that’s what I want on the right side of my shot”, then figure out what focal length gives me that field of view.

Then I look at depth of field, not aperture. Aperture’s just a number, and what it does for you is, again, relative. I don’t look at a scene and think “Right, I need to shoot f/8, how much depth of field will that give me?”. I look at the scene and figure out what I need my depth of field to be. Then taking sensor size & focal length into account, I can figure out what aperture I need to give me the depth of field I want using an app on my phone.

The above pair of screen grabs from the video are why. It just makes no sense to me to think of it in terms of focal length & aperture first. It’s like planning a trip and thinking “I have $50 worth of gas in the car, where/how far can I get on that?” vs picking a destination and then figuring out how much fuel you’ll need to get there.

I shoot Micro Four Thirds, Nikon DX, “full frame” 35mm and medium format. So, it’s always just been the easiest way for me to tackle it. Far less hassle than trying to figure out a bunch of maths in my head on the fly.

The video does get quite complex, but it’s broken down into simple and practical steps. And it’s good information to understand, even if you don’t want have to keep all the maths and technical bits in your head all the time. Because once you do understand it, properly, it’s easy for you to come up with a system that translates it into a quick method for you to remember while you’re shooting.

Eventually, you’ll just be on auto-pilot and figuring this stuff out without thinking about it at all. So, grab yourself a good drink, and watch the whole thing.

[via No Film School]

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John Aldred

John Aldred

John Aldred is a photographer with over 20 years of experience in the portrait and commercial worlds. He is based in Scotland and has been an early adopter – and occasional beta tester – of almost every digital imaging technology in that time. As well as his creative visual work, John uses 3D printing, electronics and programming to create his own photography and filmmaking tools and consults for a number of brands across the industry.

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6 responses to “Dispelling myths on sensor size, crop factor, and depth of field”

  1. Roy Bridgewood Avatar
    Roy Bridgewood

    Took me an hour to explain this I now have a ‘watch this’ video, thanks

  2. Justin Griffin Avatar
    Justin Griffin

    John Kirk Stewart Ilia Draznin

  3. Alf-Einar Trenulltre Avatar
    Alf-Einar Trenulltre

    jeez i hate people who cant make a proper video. the sound is awful, and he’s just repeating himself and being really boring. Is it so hard to present technical information without having the recipient want to blow his head off?

  4. Jonathan Keys Avatar
    Jonathan Keys

    no wonder beginners get confused,

  5. Mike Avatar
    Mike

    I will punch the next person that says ”
    A 100mm FF lens is 200mm on a m43 camera.”

  6. KC Avatar
    KC

    I’ve bounced all over the “format” spectrum, and the phrase that winds me up is “full frame”. Every camera is “full frame” to it’s respective sensor size. Granted, that’s not technically true, but if your camera is imagining on the majority of the surface of the sensor, it’s “full frame”. How “full frame” came to mean “just like 35mm!” is beyond me. 3:2 is an odd format, much like 16:9 is odd for still images.

    Now we have all sorts of discussions about “equivalence”. If this=that, then this=that, because…. I have no idea why this is important. Physics hasn’t changed. Just the recording medium.

    What the video is showing is “photo science”, the magic behind photography. Way back in film days you had to know the science, art, and mechanics of photography. Maybe. Many got along just fine without the science part.