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News & Insight

Why You Shouldn’t Apply Crop Factor to Aperture | Crop vs Full Frame

By Justin Heyes on February 21st 2018

There isn’t a day that rises where a debate on the benefits of full-frame cameras over APS-C or micro four-thirds doesn’t rear its ugly head. The argument is about as trite as the polemicists who initiate the conversation.

There are those who will stand upon their soapboxes claiming some sort of vast superiority with larger sensors. Yes, there are a few benefits to using larger sensors (ie. low light performance and dynamic range), but where truths tend to shift is the conversion from full-frame to APS-C or smaller in regards to aperture and focal length.

[REWIND: Canon 85mm Battle | 85mm 1.2L vs. 85mm 1.4L vs. 85mm 1.8]

Similar to cutting down a printed image, the field of view changes but not the exposure. In his recent video, Mattias Burling explains why he doesn’t apply crop factor to aperture.

Some would have you believe that using a crop body has the same effects as using a teleconverter. The focal length and aperture remain the same regardless if a lens is attached to a Full Frame camera or an APS-C one. An APS-C camera provides the field of view that is typically 1.5x the focal length of the lens attached – or a “crop” view.

Burling has this to add to his video, “A point that I feel gets missed and that I probably should have made clear in the video is as follows. A beginner needs not to occupy their brain with a bunch of nonsense on how to use their lens to match the look of a system they don’t own. They should learn their own system and how to expose and frame. That’s all photography is. Veterans already know what lens does what from what distance.  The notion that they need to know that their 25mm is in fact a ”50mm in case you have the same generation camera  and a similar pixel density given by resolution and are able to adjust the shutter speed (via tripod if needed) and/or shutter speed without ruining the integrity of the shot as you planned it”, is just ridiculous to me. Nowhere in old photography books do I see that kind of stuff.”

As a photographer progresses in their craft, they can absolutely apply the crop factor to their camera settings in order to achieve a similar look.

The take away is that the exposure is the same regardless of sensor size. As a photographer progresses in their craft and changes gear, they can absolutely apply the crop factor to their camera settings in order to achieve a similar look.

While it is beneficial to know that a 50mm lens on an APS-C body looks like a 75mm or 80mm on a full-frame camera for those who primarily shoot with smaller sensors, knowing how to use the system you have is more important than comparing it to another system altogether.


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Justin Heyes wants to live in a world where we have near misses and absolute hits; great love and small disasters. Starting his career as a gaffer, he has done work for QVC and The Rachel Ray Show, but quickly fell in love with photography. When he’s not building arcade machines, you can find him at local flea markets or attending car shows.

Explore his photographic endeavors here.

Website: Justin Heyes
Instagram: @jheyesphoto

Q&A Discussions

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  1. Eric Mathiasen

    Tony Northrup seems to be the guy most often credited with advocating for the idea of applying crop factor to aperture. At first glance, the idea seems insane. And, if all you ever do is buy one camera system, I’d agree that thinking about crop factor at all isn’t really necessary or even important. Tony’s whole point was for people who either use multiple systems or who are considering moving between systems to use the crop factor to help understand the dynamics of how to get similar look and feel across multiple systems, or to get the look and feel you’ve developed over years with one system when moving to a new system. Those are legitimate needs for many professional photographers and a certain subset of advanced, serious amateur photographers. Knowing that it *is* something that should be considered during a transition is relevant even if a photographer never moves between systems. For example, most photographers have favorite lenses, and using Tony’s technique will help them determine ahead of time if they will have access to lenses that let them achieve the results that made them love those lenses before making a big investment in a different system.

    Like I said, I was skeptical at first, but once I realized he is *NOT* talking about exposure, and once I saw the mass amounts of data and examples he backed his ideas up with, I am now convinced that he is correct. It’s not “every day” type of information, but it is information that pros and advanced amateurs will probably benefit from considering at least a few times in their lives/careers.

    Watch Tony’s most detailed explanation with an open mind and tell me he’s not right after you’re done watching – at 45 minutes, it takes commitment to watch the whole thing, but it’s worth it:

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  2. Doug Walkey

    Good article. Strange we never heard these arguments between 8X10,  5X7, 220 film and that tiny, untrustworthy 35mm back in the day.

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    • Eric Mathiasen

      “Back in the day” it was rare to use the same lenses across multiple film sizes. And the term “crop factor” didn’t exist. However, discussions of why lenses with the same base numbers  yielded varied looks across platforms absolutely did exist and were built into lessons on how to shoot large format for medium format shooters, or 35mm vs medium, etc. The language was different, the discussion was the same.

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  3. Vangelis Medina

    Ok, but the reason to apply crop factor to aperture is to match DOF, not exposure.

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  4. Preston Thomas

    Those Photographers and their Freudian obsession with Sensor size… Sometimes a Pixel is just a Pixel. 

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    • Eric Mathiasen

      Sure, as long as you give both pixels the same total amount of light. Otherwise smaller pixels (regardless of crop factor) will be noisier than larger ones. Tony Northrup has a detailed, well-documented discussion of noise, ISO, and pixel size as part of his 4th video about crop factor and aperture.

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  5. dave birch

    my light meter doesn’t have a button for sensor size…

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    • Eric Mathiasen

      Again, none of the discussion about applying crop factor to operator has to do with exposure. Only to depth of field, relative bokeh, and sensor noise/ISO performance.

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  6. Jesse Ortiz

    How does crop factor apply to compression? 

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    • Eric Mathiasen

      It doesn’t, but it can apply to relative noise, which can be impacted further by compression.

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  7. Ralph Hightower

    If full-frame in Swedish means tiny picture, then APS-C and m4/3 means tinier picture.

    When I was researching a DSLR to buy, I wanted a full-frame camera since I was adding digital to my 35mm film cameras. I want a wide-angle 28mm to be 28mm, not a normal lens at 45mm.

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    • Justin Heyes

      A 28mm lens is still 28mm regardless of what system you use.  The compression and characteristics will remain the same, just the FOV will change

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    • Eric Mathiasen

      Justin – the FOV changes, which may cause the photographer to alter his or her distance from the subject, which then impacts depth of field and relative appearance of bokeh.

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