If Sensor Size Doesn't Matter, Why Buy a Bigger One?

If Sensor Size Doesn't Matter, Why Buy a Bigger One?

Recently Lee published a comparison between the images from several different-sized cameras and there was no apparent difference. What's the point of buying a camera with a larger sensor then?Sensor size matters. Sometimes. You won't have the need for a bigger sensor until you know the technical side of it and find yourself in a lot of situations you would benefit from a camera having such a sensor.

The Sensor In a Nutshell

While there are "by-products" from the size of the light-sensitive chip, in general it's just a rectangular device that reacts to light. The size of the all-in-one captured frame depends on the size of the rectangle. The bigger the rectangular area, the more you will capture from the scene your camera is pointed at. It is like the window of your home. The bigger the window, the more you will see from the outside view. A crop sensor is smaller than a full-frame sensor. That's the main difference.

When You Won't See the Difference

If you photograph mainly in large spaces or outside using enough light, available or strobes, and have a modern camera, you probably won't feel the need to buy one with a big sensor. Big sensors are often less noisy at high ISO, but modern technology provides us with cameras where even micro four-thirds ones give us quite a good quality of image in not-enough-light situations. This is why I said the "window size" is the main difference, not pixel peeping.

Two photographs with two different sensors

Two photographs with two different sensors: full frame and crop. You can't see the difference.

Wide-Angle Lenses

Can't we use wider-angle lenses when we have a smaller sensor? Won't we see more? Think of using a wider lens is like squeezing your clothes in a small travel bag. You're getting your stuff in, but you don't want to put any of these clothes on without ironing them first. The same with wide lenses: they will give you more of the environment, but will squeeze the center part of it, because there's no place to fit the rest of the view and thus distorting the reality of distances between the objects in the frame. With a larger sensor you will be able to use a tighter lens, distances will be closer to reality, and you'll still see more than a smaller sensor.

Shallow Depth of Field

Most of you know, but let me say it once again: larger sensors don't give a shallower depth of field. A 50mm lens will give the same optical image regardless of the sensor size. It's the sensor that will "crop" part of the circular picture, given by the lens. All rectangular sensors do. If you have a tight shot on a small sensor and want to have the same with a bigger one, you have to get closer to the subject, because the "window" is bigger and it will show more than you need. This will naturally make the photograph with a shallower depth of field, because of the diminished distance from the camera to the subject.

Can You Simulate a Bigger Sensor?

Absolutely, but not always. If you photograph a tight interior you better not use a wide lens, but create a panorama out of several images. This will do good to the interior designer, to the viewers (who won't be fooled by the distorted perspective of a wide view), and to your portfolio. You can do the same for landscapes and even for portraits. It's a big tricky for the last case, but if you're budget is tight, you can get around that with some tedious post-processing work.

Wedding portrait panorama image

Shot as two separate images (left and right), because I had my back against the wall with a crop-sensor camera.

So, When Would You Need a Bigger Sensor?

In my opinion and experience, it's when you're constantly in low-light situations (although not such a strong argument) and in tight spaces and you don't want to use wide-angle lenses, but capture more of the view. If you have experienced more cases where utilizing a larger sensor was an absolute necessity, please tell us in the comments below.

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65 Comments

Steven Magner's picture

I shoot real estate photography. In my early years I was on a 7D with a 10-22, which was fine for the little experience and learning I was doing on the fly. Fast forward years later and I could not imagine giving up my 16-35 or my 17mm tse for the 10-22, nor would I want to pay the price of the 11-24 to compensate for the crop factor. In this case I see a significant difference in sensor size.

That said, as I have found myself moving into more architectural work and wider angle shots are way less desirable, I have considered picking up an a6400.

Tihomir Lazarov's picture

Exactly. Sensor size matters for your type of work.

Timothy Gasper's picture

I remember years ago the saying...'The camera doesn't matter...'. Well...does it? Open question for all. What DOES matter is - the lens. That is for sure.

Usman Dawood's picture

The camera doesn’t matter when you’re first starting out. The reason why many teachers say this is because many people coming into the photography industry get transfixed by gear and forget about the art.

As you progress and learn how to manage light and compose correctly the camera does indeed begin to matter. It matters a lot when you have time constraints and demanding clients. It also matters when you have clients with specific requirements.

It’s much more nuanced than this but the camera does and doesn’t matter. It depends on a number of factors.

Schrödinger's cat Lol. It’s quantum.

Will Murray's picture

Schrödinger's camera

Tihomir Lazarov's picture

Can't say it better than that.

Will Murray's picture

Does it though? Computer aided design and computer aided manufacturing mean the IQ of modern cheap lenses is still really good. I can't help but think that high resolution lenses and sensors only become meaningful in edge cases, where the user is milking every last bit of performance out of them. I always think the biggest benefit is build quality.

Timothy Gasper's picture

I'll qualify my statement.....what matters is the "light-gathering device" however it's manufactured. And, yes, you have proven the point. When you said that computer aided design and manufacturing..bla bla bla..have made IQ of cheaper lenses really good, then those lenses which have NOT gone through that process and any existing lenses (and there are so many of them, old ones especially) will fall into the lesser quality lenses. Unless manufacturers want to go through the redesigning process of old lenses. Glass DOES matter. We're not talking about new glass....ANY glass.

Will Murray's picture

Although I take your point, I can't help but reflect that one shoots old glass (or pinhole) and/or film because it has certain qualities.

"Sharpness is overrated" ~ Keith Carter

Edit: even by this standard, glass matters.

Timothy Gasper's picture

"Sharpness is whatever a photographer deems it to be". And yes...in the end glass does matter.

Will Murray's picture

That is clearly not the case (resolution and acutance); however, whatever works for you.

Timothy Gasper's picture

In the technical sense yes..I agree. But what works for one person may not be the same choice for another.

it matters a lot :) ... in some cases more than lens ..

SO... for the same field of view at the same distance, depth of field is shallower on bigger sensors... and let be real we all crop with a lens to the look we want and often restricted where we can walk, so we zoom in or out to get the shot we want... so the same field of view, different focal lengths to get the same shot. The Field of view and how I crop with the lens is a key part of my photography, as a portrait photographer I don't want to get too close to the model with a wide angle lens due to the perspective distortion that comes with it to get the same shot I get with my medium format camera. I'm likely to be at the same distance from the model whatever camera i'm using, this is likely to end up with different looks if I was using an iPhone, micro 4/3, aps, FF, MF 43.8 x 32.9, MF 53.7×40.4mm etc etc… just different focal lengths... :-)

I'm going to just let you all have this discussion. I'm out.
- signed SPDH (Society for the Protection of Dead Horses)

Tony L's picture

thanks to the internet, dead horses are being flogged on a daily basis #horsestoo

Brian Knight's picture

It's not really about sensor performance for some. Doing events would be super difficult for me without all my customized buttons which I have committed to muscle memory. My old a6500 just didn't have enough convenience controls. Last place I would want to be during a wedding shoot, is b@lls deep in a Sony menu, while missing once in a lifetime shots.

David Pavlich's picture

Gear matters, be it sensor size, body design, lens quality, tripods, flash, etc, etc. These are tools and if you want the most efficient, durable, dependable equipment, it comes with a cost. If you're serious about photography or any hobby, buy the best that your budget will allow.

The bit about WA lenses is nonsense.

"Think of using a wider lens is like squeezing your clothes in a small travel bag" WTF?
A small sensor uses a "wide angle" lens insofar as it is a WA lens in relation to a larger sensor.
50mm on a 6x7cm film camera is very wide yet no one calls a 50 wide on a 35mm frame.

A a17mm lens may seem like an UWA on a FF camera but provides a 35mm AOV on a µ43 sensor. Hardly weird or exotic.

If you use a µ43 camera you choose lenses that have the AOV you need. The FL tells you what the AOV will be on that camera. I use a Canon 11-24 extensively because I need UWA AOV on FF. If I were to use it on a µ43 camera the AOV would mimic a 22-48mm lens as far as AOV.

For the same AOV you will see the same levels of distortion or lack thereof.

This only adds to the confusion about sensor size rather than clarifying.

Tihomir Lazarov's picture

The physics of the optical transformation in wide-angle lenses shows that you have to put more stuff on one place. Wide angle - sees more, but the canvas, where light is projected, is the same. This means detail has to be squeezed (made smaller) in order to fit on the same canvas. I'm not talking about distortion here, because there are wide-angle lenses without distortion. As it doesn't project the real perception we, as humans have (which perception is based on the optical distortion of our natural lenses - the eyes), it looks unnatural and thus doesn't present reality as is: distances look exaggerated.

Matt Williams's picture

Wrong, please stop peddling this nonsense.

17mm (or 17.5) m4/3 will look like 35mm on FF. Aside from DOF. End of story.

Perspective distortion, exaggerated distances, etc. are by-products of the angle of view, NOT the focal length.

Please stop spreading falsehoods. If you don't believe me (and everyone else here telling you that you are wrong) - give it a try and post the results. Take the same picture from the same distance with two lenses on two different sensor-size cameras that have the same equivalent focal length (i.e. AOV). Provided they are both decently corrected lenses, all you will notice are DOF differences (with the same f-stop anyway).

Terry Wright's picture

So glad someone else read that and threw up a flag on the play.

Stas Aleksandersson's picture

After trying both, I have to say that I’m pleased with the full frame.
The only situation I found I wish I had a crop sensor was in Iceland when I wanted to get longer exposure not having found the ND filter for my 14mm Samyang AF. The sensor was too big and the slowest I could get was 1/20.

Tihomir Lazarov's picture

It all depends on what kind of work you're mostly doing. I've been using both and I still use a crop sensor. I do commercial portraiture when it comes to stills and full frame doesn't justify its price for my type of work.

I don't understand the argument about wide angle shots. If you use a 24 mm lens on a FF-body, but a 12 mm on a MFT-camera. Problem solved!

Tihomir Lazarov's picture

The whole issue is about the exaggerated distances the wide-angle lenses give (I'm not talking about the distortions). If you want to show an interior as is without lying the viewer it about its dimensions, you need to use a glass that will see it as your eyes do. In this case small interiors won't "fit" the sensor and you need to have a bigger sensor or to make a panorama.

Never heard of field-of-view have you? That's what it's all about. It has nothing to do with sensor size.

Tihomir Lazarov's picture

Let me put it this way. You put a 40mm on a full-frame and on a crop sensor. One "sees" more, because the light is projected onto a bigger canvas. If you put a 24mm on both full-frame and on a crop sensor it will do the same, but the image will have a 24mm look, i.e. not the way the eye sees it. If you have a situation where the architect of the interior wants an image the way the eye sees it, go and tell them that they don't understand what a "field of view" is and that you're going to use a 24mm on a crop sensor (for example) and let them deal with it. The task is about making a normal-looking shot, not about measuring distance from lens to sensor and lens' focal length.

It's about getting the job done and in this case job is done by using the "natural" looking lens on the appropriate sensor size and make a single shot of the interior OR if you don't have a big-enough sensor, make a panorama with that same lens.

Matt Williams's picture

This is not remotely accurate. What is a 24mm look? There is only FOV and of course, DOF changes with the actual focal length, but I have no idea what you're talking about in regards to seeing more or the "way an eye sees it." Does the eye "see" like a full-frame camera? A medium format? APS-C? I have no idea what this means, because it's wrong.

The only exception to what you're talking about would be distortion of ultra-wide angle lenses, but most modern lenses (especially m4/3) are incredibly well corrected. A very good 12mm M4/3 lens will look like a 24mm FF lens (minus DOF differences).

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