7 Notes on Changing from a Crop Sensor Camera to a Full Frame Camera


Perhaps you shoot with a DX camera, otherwise known as a crop-sensor or crop-body camera. Maybe you wonder about all the fuss over FX or full-frame cameras. Why do people pay more for a larger sensor and the bigger, heavier lenses to go with it?

And most importantly, Should You? Sadly, I don't know if you should. (Oh, the money I could make...) But farther down the page you'll find my recommendations.

First I want to tell you what happened when I switched from the DX-format D7000 to the full-frame D600. I had used both DX and full-frame lenses with the smaller-sensor camera. I kept the full-frame lenses, expecting an easy transition, but surprises awaited me.

In this article I use the Nikon terms for full-frame and small-sensor cameras and the lenses that are designed for them. If you are a Canonian, for "DX" read "EF-S or crop-body" and for "FX" read "EF or full-frame."

Here are the 7 most important factors I discovered in my crop-body-to-full-frame switch:

1. Relearning the focal lengths. Because of the crop factor on smaller-sensor cameras, 50mm does not have the same angle of view as it would on a full-frame camera. I knew my lenses would "act wider" on the FX camera and by how much. But I did not expect to find I had internalized their angles of view on the DX camera. I had to adjust my intuitive sense of which focal length to pick.


2. Relearning the apertures. Depth of field depends on aperture, focus distance and the real (not effective!) focal length. As a result, you get greater depth of field on a small-sensor camera -- for the same aperture and framing. Full-frame cameras seem to give you about 1 stop less depth of field. In other words, the depth I got at f/8 on the small-sensor camera would require f/11 on the full-frame camera. Again, I knew this would happen, but retraining my intuitive choice of aperture took some practice.


3. Relearning the sharpest settings of each lens. All zoom lenses have aperture/focal length combinations that are less sharp than the best the lens can do. For example, a 24-70 might be sharp at f/2.8 between 30mm and 60mm, and less sharp wider or longer than that. I had gotten used to the strengths and weaknesses of my full-frame lenses. But on FX, the story is different. It turns out lens sharpness depends partly on the size of the sensor.

Lenses are designed to throw a particular image circle with a particular sharpness. They're always sharper in the center. Record a smaller central part of the image circle, and you would expect a sharper image overall. Such is not always the case, mon frère!

Sure, it sounds crazy. Visit DXOMark.com and compare the same lens on cameras of different sensor sizes (and equal pixel counts) if you don't believe me.


4. Getting used to the viewfinder. Full-frame cameras have bigger viewfinders (as long as we're talking about optical viewfinders here). On my small-sensor D7000 it was easy to see the frame edges because the viewfinder image was smaller. With the new full-frame D600, at first I framed everything extremely loose and wondered if my sense of composition had evaporated overnight. I had to pay special attention to the frame edges in the viewfinder in order get my framing right.


5. Relearning the sensor. Newer cameras get better technology in the sensor, which means less noise and better dynamic range. In my particular case, the new camera's sensor was made by a different company as well. It took a month of shooting and testing to understand how the new sensor would behave. The differences are all good: dynamic range so wide I have trouble over-exposing anything, nice subtle color variations, and no worries about noise in any of my normal shooting situations.

We're always working within the constraints imposed by the medium and the tools. Constraints are good for creativity, because then your brain has fewer possibilities to sort and combine. The way your lenses and sensor behave under various conditions get quietly noted by your intuitive mind, and you use that knowledge to make decisions. To pre-visualize the finished image, you have to understand how the lenses, sensor, software and printing processes will react. Even if your gear improves, your intuitive mind must get used to the new features of the system.


6. Adapting to the focus points. In my case, the pattern of focus points remained the same. They're also the same size. The trouble lies in the fact that the viewfinder image is much larger on the D600. Now the focus points cover a lot less of the viewfinder image. We must always adapt to our tools, right? Yes, it's only the 21st century. Now I use the focus-lock button more. It's pretty much focus, lock focus, recompose, shoot.


7. Correcting distortion. PTLens has always been one of my favorite plugins, partly because it will correct the distortion you get using an FX lens on a DX body. Adobe Camera Raw (or Lightroom) won't do that. With full-frame lenses on a full-frame body, I get the extra convenience of correcting distortion in ACR before opening the photograph in Photoshop. It's a little faster overall for each image, and for a big batch of them, hell yea!


:: A Few Points About Full-Frame Lenses

  • To illuminate that larger sensor, full-frame lenses have to be larger -- especially the fast zooms. That means heavier, and possibly a lot heavier. More than one photographer suffers from back problems from carrying heavy lenses. You really want a balanced load, like you get with a backpack-style camera bag.

  • Full-frame lenses look impressive to clients. Yes, put the lens hood on even if you don't need it. Big gear shows you are serious and professional, just like wearing a tie.

  • Full-frame lenses may focus faster. This is important for any situation where you have to capture fleeting moments. It's nice to know you get that for the extra money. Isn't it?

  • You don't want to use DX lenses on a full-frame camera. Yes, Nikon makes that work technically, but you have to compose inside a small rectangle in the viewfinder. The full-frame viewfinder shows precisely how small that DX lens image circle is, and all the vignetting, and the shape of the lens hood. It's a nasty way to work.


:: But Should You Change to Full Frame?

I knew you would ask that. Here are some advantages of a full-frame camera:

A. Wide angle lenses are less distorted on full-frame cameras. If you need to see a well-corrected view in the optical viewfinder when shooting at 24mm or less, full frame is better. Why? It's easier to make undistorted 24mm lenses than undistorted 16mm lenses (the equivalent focal length for DX). Lens makers generally choose sharpness over geometric accuracy, and the wider the lens, the more extreme that tradeoff.

Nowadays you can work around that somewhat by turning on the auto-distortion-correction feature. The LCD view will show you the corrected image. You'll still have to correct your raw file in processing, but this is a useful approach when photographic static subjects.

Please note that I'm talking about lens distortion here, not the effect of a wider angle of view. They are two entirely different things. The crazy way things look with a much wider than normal angle of view is available on both full-frame and small-sensor cameras.


B. You get more bokeh. If you like that blurry background, a full-frame camera will blur it more at every aperture. To get the same effect on a crop-sensor camera, you'll need fast prime lenses. Prime lenses tend to have better-looking bokeh than zooms, too.

A good compromise for your small-sensor kit would be one fast prime for portraits, because candid or outdoor portraits normally call for lots of background bokeh. Trouble is, the common 50mm (75mm effective) is a little too wide and the traditional 85mm (127 effective) could be considered a bit too long for portraits. 60mm gets you around 90mm effective, but the fastest 60mm lenses I know of have a maximum aperture of f/2.8 -- not as fast as most portrait photographers would prefer. It makes you wonder why.


C. You could get sharper pictures at large apertures. Whatever amount of bokeh you have in mind, a full-frame camera will give it to you at a smaller aperture. Most fast lenses are not as sharp at their largest apertures. So if your choice of depth lands at, say f/1.4 on a small-sensor camera, you'll get the same depth on a full-frame camera at f/2. Plus the sharp parts will be sharper because lenses are almost always sharper at f/2 than at f/1.4.

The size of your sensor makes little to no difference at middle and small apertures, because lenses are about equally sharp at f/5.6, f/8 and f/11. You already know from point 3 above that lenses are designed for specific sensor sizes; I'm not saying you'll get sharper pictures on full-frame with the same exact lens. They'd have to be 2 lenses of the same focal length and maximum aperture, each designed for the their respective sensor sizes.


D. Full-frame lenses tend to perform better. Well, for those prices, they sure as hell should! Photographers like to say, "It's all about the glass." If that's true, you want full-frame lenses. And a camera to match.

I personally have found that:

  • Small-sensor lenses don't always meet my persnickety requirements for distortion and sharpness.

  • Full-frame lenses do. Some of them are downright awesome.

Keep in mind I use Nikon, so you'll need to verify -- or refute -- this with your brand.


:: The Case Against Full-Frame

Here are some solid advantages of a small-sensor camera:

A. Weight. Any DX body and DX lens will weigh less than the equivalent full-frame setup. Pretty much anybody can walk further carrying less weight. If your photography happens quite far from the car, this is an important consideration.

Other ways to deal with the weight disadvantage are:

  • Use lenses of smaller maximum, or variable-maximum-aperture.

  • Hire gorillas.


B. Cost. You've seen the prices. You know exactly what I mean.


C. Stealthiness. Small-sensor cameras are smaller overall. Many times the zoom lenses are of the small, varying-aperture type. The kit looks like millions of others, hanging off the shoulders of people of every description, the world around. You could be the next Pulitzer-Prize-Winning photographer and nobody would suspect a thing.

And yet, if stealthiness rules your decision process, why not get a Micro 4/3rds mirrorless camera? They fit into large pockets, unassuming tote bags and medium-capacity purses. No camera bag to give you away! Just remember, the smaller the camera, the harder it is to get much bokeh -- especially with zooms.

Camera engineers don't know how you want your photographs to look.

What's that? Why not use a camera phone? I'm going to say no, just no. Look, the medium of photography has 12 formal tools: means of expression inherent to the medium, the elements from which you build images. Camera phones and the usual process of using them take away your control over 6 of them. That means the camera phone engineers are making half of your creative decisions. They are a brilliant bunch, but they will never know what you want to say in your photographs.

But my views on personal accomplishment may be different from yours. I also cook without recipes. I despise craft kits. I cringe at the attitude behind saying "Look what I did!" while showing the paint-by-numbers masterpiece. Feel free to use all the Instagram-style shortcuts you want, but don't call it your creative work, because that would be deeply sad.

Did somebody say "casual snapshots"? That's not what we're talking about here. Define your process with "it doesn't matter" and I stop listening. Hmmm hmmm hmmm. Can't hear you.


D. Telephoto. On the telephoto end, the crop factor becomes your friend. The unassuming 18-200 becomes a 27-300! By contrast, you could improve your biceps lifting a 300mm lens for a full-frame camera.

This is nothing to sneeze at. I wouldn't be surprised to learn of a photographer extending the reach of a telephoto lens using a small-sensor camera instead of a tele-extender. She would get the optical quality of an un-extended telephoto at 1.5 times the focal length. That 300mm goes from pretty long to a bird-worthy 450mm, without adding any distortion or reducing the maximum aperture. The price difference between a Nikon 300mm f/2.8 and a Nikon 400mm f/2.8 is, today, $3200. You can buy the best DX camera Nikon makes for $1200. (scribble, scribble) I make the savings two entire kilobucks, plus you get another 50mm free. Who wouldn't take that deal?

Of course these are FX telephoto lenses we're talking about, so the weight savings of DX have vanished. If you need beasts like this for your work, you don't care. You mount them directly onto the Wimberly head with the camera body hanging off the back. Nothing else will do.

Again, be sure the FX telephoto will be as sharp as you need it to be on that smaller-sensor camera. The engineers did not have a DX camera in mind when they tweaked up the design tradeoffs.


:: Conclusion, If You Can Call It That

Sharpness isn't everything. Bokeh may not even have occurred to you. I personally am not interested in capturing the Raquet-tailed Drongo at play, but you could be. So here's your most-likely path to a good decision:

1. Figure out what you most want to photograph.

2. Write down what factors will lead to success: sharpness, bokeh, weight, telephoto reach, cost, focusing speed, a corrected viewfinder at wide angles, stealthiness or the opposite, or none of the above.

3. Choose according to the factors.


:: Perhaps an Easier Way

If that's too much work, you could choose a kit according to the general type of photography you do below (But don't blame me if it turns out wrong. I don't know your intentions.):


Portraits: Full-frame with a fast 85mm prime. Add a 50mm or normal zoom for groups. For parties, add a flash setup.


Landscapes: Full-frame with a top-quality wide angle lens, if you're the "get it in the camera" type. Otherwise you can get by with a less-costly kit.


Food, Products: In food photography you often want lots of bokeh, so choose prime lenses. Ideally these are tilt/shift primes, which are made for full-frame cameras. For products you usually want very little bokeh at close focusing distances and no keystoning, so again, go with tilt/shift primes.


Vacation: The smallest, lightest small-sensor camera with a lightweight zoom will stand the best chance of leaving the hotel room with you. But who are we kidding? You're either on vacation or you're making photographs.


Wildlife: DX and a honking telephoto prime, if you've rented that combination and find it works. Add gorillas or an anti-grav sled.


Nature, Hiking: DX and a good quality walk-around zoom. Maybe a macro lens as well.


Sports: Most of us must wait for the action to get close anyway, so about any kit with a longish zoom that focuses quickly will work fine. We'll revisit this when we can fly cameras on drones over the field.


Weddings: You're getting paid plenty, so look like a Professional Photographer with a full-frame camera and top-quality lenses. As for the exact kit, find out what the long-time wedding photographers prefer, and don't be surprised if they mention old manual lenses for the creamy bokeh.

If for some reason you are not getting paid, sit down in a corner and consider the job you just took away from a professional photographer.


News: From what I hear, news photographers use whatever the publication gives them. Some prefer a wide zoom on a small, nimble camera. Others carry one body with a tele zoom and one with a normal zoom, for speed. I personally would choose DX for photojournalism.


Celebrities: If someone let a paparazzo in here, I shall need to speak to the head of security immediately.


Funny Cat Pictures and Other Amazing Unrepeatable Sights: The best camera is always the one you have with you. Yes, including the camera phone. Sheesh.


I'd love to hear what you think of all this. Contact me

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