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I'm trying to decide on a higher-end digital SLR, and I'm down to choosing between an APS-C model and a full-frame model.

I understand that the sensors are of different sizes, and as such have an effect on the perceived magnification of the lens, with the smaller APS-C sensor having an effective focal length greater than what it otherwise would be with a full frame sensor. But why does this matter?

  • What things should drive my choice between one or the other?
  • In which situations is one better than the other, and why?
share|improve this question
Related, perhaps a duplicate: – Reid Oct 15 '10 at 23:21
Have spent hours researching aps-c Vs FF. I would appear for taking group photos of 50 people I would be better off with a APS-C camera as they would sharper at the corners as well as less vigenetting. Any thoughts? – user6044 Jul 22 '11 at 9:46
@Allen: good question — I think worth asking as a new question. – mattdm Jul 25 '11 at 2:36
See also Is crop-factor a bad thing? – mattdm Sep 3 '11 at 3:02
See also: Roger Cicala of on "The Full Frame Move". – inkista Jun 2 '14 at 23:47
up vote 121 down vote accepted
  • One major difference is that a FF camera produces a depth of field that's around 1.3 stops shallower than an APS-C camera for the same subject & framing. This is most important when you have the aperture as wide as possible, e.g. for portraiture. To replicate the look of a 50 f/1.4 lens you'd have to use something like a 31 f/0.9 lens, which doesn't as far as I know exist!

Quick and dirty comparison image, APS-C Canon 30D left, FF Canon 5D right, same lens (FF image was zoomed in, however to give the same field of view), same composition, both f/2.8

  • Another difference is that if you're using a lens designed for a full frame camera (like all Canon EF lenses) you are making full use of the image circle, which is less demanding of the optics and so you can expect a sharper image for the same number of megapixels. It's true that some lenses get softer toward the edge of the image, but you will still get higher average sharpness with most lenses, and telephotos will be sharper right across the frame. The crop factor of APS-C cameras takes the middle out of the lens and blows it up, losing sharpness in the process in a similar manner to a teleconverter.

  • Larger formats allow for sharper optics. One of the driving forces for larger formats (other than the relatively constant resolving power per unit area of film) has been that it allows lenses to be produced which resolve a greater number of line pairs per picture height. Going full frame on a DSLR benefits from this to an extend - see: With all other things equal, in a DSLR, will a larger sensor produce a sharper image?

  • A bigger sensor means bigger pixels, which in turn means you capture more light usually achieving lower noise levels in the process. Greater dynamic range goes hand in hand with this.

  • You get a larger, brighter viewfinder on a full frame camera, which can be helpful composing shots. Having said that, I personally find the 5D viewfinder too large, I've not used a 7D but it has a very high spec 'finder.

  • You have more mirror to move on a full frame camera. The larger mirror used to mean shooting speed is limited (the mirror on my 5D moves so slowly I can actually see the world slide sideways/up for an instant) however high speed full frame models are now available.

  • Likewise the mirror box, focussing screen and pentaprism are larger, meaning the camera is larger and heavier.

  • Lens hoods are designed for FF image circle and are therefore slightly more effective on FF cameras. This mostly applies to prime lenses, as zoom lens hoods are designed cut to accommodate the widest zoom setting, so everything else is already non optimal. If you're using an EF lens on a crop camera you ideally want the hood tighter (since the extra shading will lie outside the smaller sensor a tighter hood wont vignette.

I have nothing against APS-C cameras but for any format it makes sense to use lenses designed for your sensor size. The range of EF-S lenses is smaller than the range of EF lenses. However for some uses (sports etc.) the smaller sensor size is helpful for the extra reach and speed it allows. Also the better noise characteristics of a FF sensor don't quite make up for the higher ISO you need to use get the same exposure when stopping down to match the DOF as a crop. So if you have to maximise DOF crop has a slight edge.

If there are EF-S lenses available for what you want to shoot then it wont be noticeably worse choosing this camera. However I feel full frame gives you more flexibility (speed aside) - as you can get the same deep DOF as a crop, but go narrower if you need to.

share|improve this answer
Matt, I like your answer, thoughtful and complete. Given the obvious advantages of the FF sensor I nevertheless find that I get outstanding quality on my APS-C DSLR. To me, at least, it seems the improvements are merely incremental. I suspect that some important advantages accrue not from the sensor but from the fact that FF bodies have in general more advanced specifications. – labnut Oct 15 '10 at 12:31
@labnut The area where you really notice the difference is with fast wide lenses, there's simply nothing available for APS-C that can match the 24 f/1.4L for speed and field of view. The ability to get nice blurred backgrounds when shooting wide is pretty much exclusive to full frame. But yeah you can still get amazing results in 90% of cases with a crop. Look at how long Nikon went without FF in their lineup. I disagree that the difference can be accounted by FF cameras being higher spec, the 7D beats the 5DmkII on pretty much everything but sensor size and MP and the 50/60D are close. – Matt Grum Oct 15 '10 at 13:48
Some other points, perhaps harder to quantify: increased micro-contrast, or fine tonal transitions. The smaller you go, the more you seem to lose. Then, all else equal, low light performance simply due to more photons, dynamic range and color depth. – Eruditass Oct 15 '10 at 17:01
The viewfinder on the 7D is a 1:1/100% viewfinder, however since that is an APS-C sensor, it is smaller than the 5D's. The 7D's finder has some pretty advanced active display stuff since it uses an LCD to display information across the whole surface of the viewfinder. – jrista Oct 15 '10 at 18:51
@Matt - ok, that explains it (but it is not quite the same lens per-se?). It would be nice also to demonstrate how you can get the same DoF with a smaller aperture on the FF. – ysap May 4 '11 at 22:09

Remember that full frame is not explicitly better than APS-C, it's just 'different'.

It's perceived as better because shallow depth of field is very trendy, and that's the advantage of full frame, and for the portrait work I do it's invaluable, and even more important is the fact that I can shoot a scene at f2.8 and have it sharp, if I shoot the same scene on a crop and want the same bokeh then I have to shoot at f1.4 and it's significantly softer.

In fact, if you need maximum depth of field then full frame becomes a disadvantage. For example I shoot 3 or 4 models at a time and need the depth of field to cover them, this requires a very small aperture- like f8, this then requires a lot of light to fill the scene. If I shot the same scene with a crop camera I can get away with f5.6, and half the lighting power- the tradeoff being that the 5d files will be sharper, and allow me to crop in more, but if the shoot doesn't have the budget to cover the lighting costs then the small increase in sharpness is moot.

I shoot both full frame and APS-C because I need to use them both for different purposes. I'm even considering dropping down to micro 4/3 because I could have a use for that too (i.e. maximum depth of field at large apertures with minimal lighting)

share|improve this answer
Welcome! Nice answer. – Evan Krall Apr 15 '11 at 4:54
for minimum DOF, use a view camera :) – jwenting Jul 22 '11 at 13:04
But you could shoot at f8 in the full frame and double the ISO and you would still have about the same quality as with the APS-C at f5.6, right? – Damian Oct 19 '13 at 19:51
Yes @Damian it is right what you write. That point written in the answer should be removed. – OlafM Nov 10 '15 at 10:48

Two very good answers already, but I want to chime in that isn't necessarily related to Crop vs FF, but rather your ultimate decision: 7D vs 5D Mark II.

While the 7D and 5D2 have different sensors, they are also geared toward different usages.

The 5D2 is not really designed with shooting action. It works (I use it), but the 7D is better with a higher precision AF, and machine-gun like burst shooting.

In general:

7D = sports, bird in flight, action
5D2 = studio and landscape

You can intermix the two with good results, that is each bodies strengths.

share|improve this answer
In my experience if you try mixing formats then it can be annoying, or at least I found it so when I used an APS-C body for a while as a backup. – philw Oct 16 '10 at 13:56
phil: I felt the same using an amateur APS-C body as a backup to my pro APS-C body. The reduced capabilities (light meter, slower AF, smaller viewfinder) are far more important than the sensor size (though if you have a lot of DX size lenses in your mix that's another problem of course) – jwenting Jul 22 '11 at 13:06

The main stylistic reasons revolve around the ability to capture wide-angle shots (although less of an issue with wider EF-S specific lenses) and that a larger physical sensor allows for a narrower depth of field (for a given aperture/focal length)

In additions, on a technical level, a larger sensor also allows for lower pixel densities, which can improve low-light performance.

share|improve this answer
Thanks Rowland. So, does that mean that a full frame is more suited to landscapes and such? Would a 7D, for example, be particularly poor for shooting landscapes, or would an amateur not notice the difference? – Winston Smith Oct 15 '10 at 8:12
There are good wide-angle EF-s lenses for example the excellent 10-22, there are just more options for wide-angles on a full frame. The 7D won't be poor for landscapes by any stretch of the imagination, but the 5D mkII will be better. – Matt Grum Oct 15 '10 at 9:06
@Winston I've recently upgraded to a 5D Mk 2, so I have a little bias on this, but as I don't need to faster performance of the AF on the 7D (I don't generally shoot sports, nor am I trying to photograph people that don't want to be), then the 5D was a better investment (even though rumours are picking up about a replacement). – Rowland Shaw Oct 15 '10 at 11:08

@Matt Grum has already given a rather comprehensive answer talking about the advantages of going full frame. But there's a flip side to using APS-C, which for certain uses gives it an advantage over FF.

Precisely because FF cameras use the whole image circle, images can suffer from vignetting, even when using otherwise excellent lenses. This can of course often be eliminated by simply stopping the lens down, but doing that negates the DOF advantage that a FF body provides.

While FF is great when looking for wide-angle shots, a crop-sensor body gives you more bang for the buck when buying long telephotos. Even if you were to buy the Canon EF 1200 mm f5.6 L lens to maximise your telephoto range on an FF body, all other things being equal, an APS-C body would still turn it into an 1920 mm f5.6 lens. This means that I could buy the 400 f4 L IS instead of the 600 f5.6 L IS to get the equivalent framing, and save a whopping $7000 or so! This is why most of my wildlife photographer friends end up choosing APS-C bodies.

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The main problem with the 7D is not the APS-C sensor, it's the 18 million pixels squeezed onto it that's it major weakness, meaning soft images unless very good technique / fast shutter speeds are used.

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All else equal, I can't see how this would be a disadvantage to - say - a 10mp camera: if you take the 18mp and resize to 10mp in photoshop, it will probably be sharper than if it has be shot in 10mp in the first place (the same if you take the 10mp and resize to 18). You are shooting to print/view inside a given area, not for louping at 100% zoom. – Marco Mp Jan 31 '13 at 10:07
The problem with softness and the 7D has nothing to do with the pixel pitch. It has a fairly strong AA filter (that softens more than the AA in the 50D, for example). The in-camera sharpening settings are also different than for previous Canon APS-C bodies. A sharpening setting of 2 or 3 in the 7D yields about the same results as a sharpening setting of 1 in previous bodies such as the 40D, 50D, etc. – Michael Clark Nov 9 '13 at 19:23

APS-C versus FF is all time debate. I try to use simple camera with simple function. This gives me time to concentrate on composition. I feel i should use FF if really they want big printouts, otherwise APS-C format is good. Buy good "L" lens, for good sharp results.

share|improve this answer
What advantage does FF provide for big printouts? – Imre Dec 12 '12 at 13:14

protected by jrista Feb 5 '13 at 5:27

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