Advantages of full frame?

[adam]

I'm curious about the advantages of shooting full-frame versus shooting crop. I've read various assertations that switching from a 40D to a 5D is like upgrading all of your glass, that a crop body gives you extra "reach" when using telephoto lenses, that you'd get similar quality shooting with a crop body as you would shooting full-frame and croping in post, and that the real image quality difference in full-frame comes when you shoot at high ISOs. So which, if any, is it?


I'm pondering what I'm saving my money up for...not in the immediate future, but probably a few months down the road. Among other things, I do a lot of airplane photography...say I took a picture of a plane with a 300mm lens and the plane filled the frame on my 40D. Now, say I took a picture of the same plane with the same lens at the same distance with a 5D and cropped it in Camera Raw such that the plane filled the frame. Which picture would be sharper?


(I don't shoot at high ISOs, but I do quite a bit of landscape/cityscape shooting where the more detail the better, so I'm already fairly certain a full-frame body would make that look nicer.)

[Colin]

With a full frame, you can use the entire full size lens, collect more light, and any errors in the optics will be relatively smaller in proportion to your image. You also get a more shallow depth of field with a given lens aperture, because the wider angle of view means that you can get closer.


A crop body focuses your pixels in a smaller area. it effectively crops the image for you, so you don't waste your pixels if you would have cropped anyway.


A crop body has an advantage if you arelikely to crop anyway (telephoto/macro), and you can then use the EF-S line of lenses as well.


However, if you have the glass for it (and don't mind carrying it) I'd lean towards a full frame.


If you can get a full frame body with pixel density the same as the crop body, the only advantage of the crop body would be smaller file sizes. Technically, ignoring a host of other parameters, the crop body and the cropped full frame body would have identical resolution with the same lens.

[Daniel Browning]

I've read various assertations that switching from a 40D to a 5D is like upgrading all of your glass,

Correct. All EF lenses have MTF curves optimized for full frame, so there is higher contrast and sharpness for a given print size.

That a crop body gives you extra "reach" when using telephoto lenses

True.

that you'd get similar quality shooting with a crop body as you would shooting full-frame and croping in post

That's only true if the FF body has the same pixel size. For example it's true when comparing the 5D2 and 20D: both have the same reach because they have the same pixel size. But the 50D is far superior to the 5D2 for reach.

and that the real image quality difference in full-frame comes when you shoot at high ISOs.

High ISO is one of the biggest, most important reasons to shoot full frame (and is one of the principle reasons that I do), but it's certainly not the only reason. Even at low ISO there are differences, such as higher dynamic range and better contrast.

say I took a picture of a plane with a 300mm lens and the plane filled the frame on my 40D. Now, say I took a picture of the same plane with the same lens at the same distance with a 5D and cropped it in Camera Raw such that the plane filled the frame. Which picture would be sharper?

The 40D would be sharper by far. The 50D would be better still.

(I don't shoot at high ISOs, but I do quite a bit of landscape/cityscape shooting where the more detail the better, so I'm already fairly certain a full-frame body would make that look nicer.)

Yes it would.

I'm curious about the advantages of shooting full-frame versus shooting crop.

There is a huge price premium to pay for a full frame sensor.

In new cameras, the 50D and 5D2 are similar enough to compare for this purpose (although the 50D has better autofocus, gapless microlenses, and an all new sensor with gapless microlenses instead of a copy of an older sensor with a few CFA changes).

The build and features of the 5D1 are similar to the old 20D.

20D used: ~$300
50D: $1200
5D1 refurb: $1400
5D2: $2700

$2700 - 1200 = 1500. There is a $1,500 price premium just for the sensor size alone. If you compare the 5D1 to the 20D, the premium is closer to $900. In other words, if you didn't really need the sensor size, you could save $900 and just buy a 20D.

Is sensor size really worth that much to you?

The answer depends on your need for the benefits that go along with full frame:

The big three, IMHO, are:

* Lens availability.
* Control over depth of field.
* Increased light gathering power.

For example, there are no wide angle primes for APS-C (EF-S), but there are dozens available on full frame. The 14mm f/2.8 on full frame would be most similar to a 9mm f/1.8 on APS-C, but there is no such lens for APS-C. The 24mm f/1.4 would be similar to a 15mm f/0.9 on APS-C, but again no such lens exists. The widest prime built for APS-C is the Sigma 30mm f/1.4, which is equivalent to a 50mm f/2.2 on full frame.

By "equivalent", I mean they would have the same field of view, same depth of field, same diffraction, and same light gathering power (light intensity times total area).

To me, those are the main benefits, but there are more:

• Larger viewfinder.
• Using EF lenses as designed (e.g. 17-40 becomes a "super wide angle" instead of a "normal")
• Higher contrast from EF lenses.
• Higher resolution from EF lenses.
• Higher dynamic range.
• Lower noise, especially shadow noise.
• Better low light capability.

If you upgrade to full frame, but you can't afford a lens that is long enough, and you have to crop the sensor down to APS-C size anyway, then you've effectively thrown away all that sensor you paid for.


For example, 200mm f/2.8 on APS-C is similar to 300mm f/4.5 on FF.The 55-250mm f/4-5.6 IS is equivalent to a 100-400 f/6.4-9.0 on FF, but the 100-400 we do have has much wider aperture than that.


So if there is a longer, slower lens available for full frame, with similar autofocus capability, then you can upgrade and still get similar photos. But Canon often does not make a longer, slower version of the lens we're using on APS-C, and if they did, it wouldn't autofocus.


The only time you will get a benifit from full frame is if you actually *use* the full frame, which rules out cropping. For that reason, the 50D is the best choice for airplane photography on a limited budget.

[Colin]

Err... I meant what Daniel said... []

[Tom Alicoate]

That was a lot of great advice. One other benefit to Full frame is that of diffraction. It is a little complicated and I am not the person to explain it, but diffraction for landscapes where you want to get a large amount of the photo in focus can be difficult with an APS-C sensor without also getting some of the blur associated with diffraction.


I have thought about this long and hard too. I have almost decided that instead of the 5DMKII, I will go with the 60D whenever that comes out. I want thelower noiseof the Full frame, but I can't loose the higher pixel density provided by the XXD series. I can't afforda lens longer than 400mm, and a high quality photograph with a littlewolf is not nearly as desireable to me as a larger wolf with a little bit of noise.


Of course in a perfect world I would have the funds for a 5DMKII for portraits and Landscapes, and an XXD for nature and aviation photos. []


Tom

[Daniel Browning]

Thanks for the post, Tom. I too would prefer a detailed, but noisy wolf. I have a comment about one thing, though:

One other benefit to Full frame is that of diffraction. It is a little complicated and I am not the person to explain it, but diffraction for landscapes where you want to get a large amount of the photo in focus can be difficult with an APS-C sensor without also getting some of the blur associated with diffraction.

That idea is believed by many respected photographers and is a widely held position on many forums, web sites, and magazines. You are in good company. However, it's actually a misconception.

The reality is that diffraction is the same for all cameras, no matter the sensor size, because it scales in perfect proportion with depth of field.

For example, let's assume a 30x20 print size viewed at a close distance with a high acuity. If made from a full frame camera at f/22, it will have reduced contrast caused by diffraction. To get the same depth of field on APS-C, one needs to only stop down to f/14. Stopping down to f/22 would cause the APS-C to have *deeper* depth of field than the full frame camera, and that is not necessary, desirable, nor comparable. Instead, it should have the same iris diameter (focal length divided by f-number) in order to have the same angle of view, perspective, and depth of field.

The same 30x20 print made from an APS-C camera at f/22 will have *much* worse diffraction softening. So on the face of it, one might draw the incorrect conclusion that full frame has an advantage with regards to diffraction. But it doesn't, because the APS-C doesn't *need* to stop down to f/22 in order to get the same depth of field.

The diffraction is the exact same on both. It scales to all sensor sizes. On an 6x9 medium format camera (84x54mm), f/22 causes much less diffraction bluring, but the depth of field is much thinner than on 35mm. To get the same depth of field, one must stop down the 6x9 lens to f/51, but then the diffraction is back to being the same.

It goes in the other direction, too. A digicam (9x6mm) only requires f/5.6 to get the same deep depth of field as f/22 on full frame. And diffraction, too, is the same on a digicam at f/5.6 as it is at f/22 on FF35.

Essentially, diffraction and depth of field are the same on all cameras of all sensor sizes. The only difference is that larger sensors may have the *option* of using thinner DOF (and the reduced diffraction that goes with thinner DOF). If the large formats are used at the same DOF, then diffraction too is the same. Other things scale with DOF as well, including low light capability.

In short: diffraction scales with DOF, no matter the sensor size.

[Jon Ruyle]

that you'd get similar quality shooting with a crop body as you would shooting full-frame and croping in post

That's only true if the FF body has the same pixel size.

It's also true if something other than pixel density is the limiting factor in image quality.

[Tom Alicoate]

Daniel,
Yep, thats why I didn't pretend to know anything about diffraction. It looks like I need to get my photo books out again. I was confused by some of the talk when the 50D came out, around seeing diffraction when stopping down.This was not due to the sensor size it was due to the decreased pixel size and I forgot about that. It is in fact good news that an APS-C camera can get the same DOF as a FFwithout stopping down as much. In fact one of the things I have noticed with my lenses is that there is anoticeable increase in sharpness closer to the sweet spot of the lens.For landscapes I am actually better off trading in some of that DOF for increased sharpness by opening things up a little, say to f8, orf11, rather than f22 or higher. I have not completely thought through this idea yet so I will pose it as a question. Does this mean that if DOF is a goal, and keeping a lens close to its sweetspot is a goal, than a APS-C sensor actually has some advantage here?


Thanks for an interesting thread!


Tom

[ShutterbugJohan]

If made from a full frame camera at f/22, it will have reduced contrast caused by diffraction. To get the same depth of field on APS-C, one needs to only stop down to f/14. Stopping down to f/22 would cause the APS-C to have *deeper* depth of field than the full frame camera, and that is not necessary, desirable, nor comparable.

What? I would think that it would be the opposite.


For example, assuming we use the 5D1 and 50D as examples; the 50D would have to have the aperture stopped down much farther than the 5D1 would for the same depth-of-field*, because the circle of confusion changes, and the 5D1 would render as sharp somthing that the 50D, with it's higher pixel density would render out-of-focus. Right?

Instead, it should have the same iris diameter (focal length divided by f-number) in order to have the same angle of view, perspective, and depth of field.

I understand all those terms, but not that statement; would you mind explaining what you mean a little more simply?


Thanks!


--Johan


* At least at the pixel level; maybe it would be different at equal print/output sizes?

[Chuck Lee]

adam,


This article is why I purchased a used 5D even though I have a 40D. http://www.kenrockwell.com/tech/full-frame-advantage.htm


Headdresses quite a few assumptions.


Good read,


Chuck