Wednesday, March 6, 2013

Wednesday Commentary: Should I Move To Full Frame? Part 4

Throughout this series on moving to full frame cameras the focus has been on what users need to consider when switching formats. This final segment of the series takes a different approach and asks the toughest question, do you need to switch to the 35mm "full frame" format? Does full frame offer what you really need as a photographer, why are crop sensor cameras not good enough and should you wait until the next generation of high end crop sensor bodies are released before you make a decision?

The marketing departments at the Canon, Nikon and Sony have been working overtime the last few years to drive users towards 35mm "full frame" cameras, even to the point that they introduced entry level bodies like the D600 and EOS 6D. There are plenty of reasons why the 35mm format has become attractive, better noise performance, thanks to physically larger pixels, and superior light gathering abilities, due to a larger imaging surface. Although full frame sensors offer superior performance, there are also some equally compelling reasons not to switch from a crop sensor format. Those reasons, not to switch formats, will be the topic of discussion today.

In some ways this is a reiteration of what has been pointed out in the previous three parts of the series, but putting them together, and expanding on those thoughts, may be helpful.

Full frame cameras allow users to frame images based on the "native" focal length of a lens, at least relative to 35mm film, but does that inherently make full frame a better format for photography? The answer to that question depends on the type of photography you do. For landscape and internal architecture that may very well be the case, since a wider field of view can be achieved with a longer focal length. Even 11mm, non-fisheye, lenses on crop sensor bodies will not give the same framing as a 14mm lens on a full frame camera. That is important because distortion will increase as the focal length gets wider. On the other hand, for telephoto work cropped sensor cameras allow tighter framing, giving the appearance of a narrower field of view. That tighter framing can be advantageous if you are a wildlife or sports photographer that cannot afford to buy 400mm lenses.

Although full frame cameras have physically larger viewfinders, to match the larger frame, the magnification of the viewfinders found in some higher end crop sensor cameras are higher. What difference does magnification have? Magnification notes how close to life size the items in the frame appear to your eye.

In addition, auto focus points cover a different part of the frame on full frame and crop sensor cameras. For example, the next images are of the D300 (crop) and D700 (full frame) viewfinder's auto focus area coverage. Both cameras have a similar 51 point auto focus system. The actual area covered is the same (this is apparent when the D700 is in DX crop mode), but the frame of the 35mm camera is larger, making the auto focus area seem smaller.

D300 AF Area Coverage (100% Optical Finder)

D700 A Area Coverage (95% Optical Finder)

This different coverage area may have an affect on how you work as a photographer, particularly if you find yourself using the focus points closest to the edge of the frame on a crop sensor body.

Lenses and Depth Of Field:
If you already have a good set of lenses designed only for use on crop sensor cameras, switching can be an expensive process. This is particularly true in the case of super wide angle zoom lenses.

You may have heard of the narrower depth of field advantage of full frame cameras, but that is a bit of a miss understanding of what is happening. If you are using a 24mm lens on a crop sensor camera, to achieve similar framing to that of a 35mm lens on full frame camera, there will be increased depth of field, compared to a 35mm lens on a full frame camera. Why? This apparent increase is due to the greater depth of field from using a wider angle lens. This in effect creates the narrower depth of field myth, that some claim full frame bodies have. The reality is that the depth of field for a given lens does not change, while the area you can photograph with the same lens on full frame vs a crop sensor body does.

Conclusion: Do You Need A Full Frame Camera?
Based on the points above, ask yourself if purchasing a full frame camera is right for you? Are the 1-2 stops of superior noise performance, and different framing important for the type of photography you do? Also factor in the cost of upgrading any lenses and accessories have to be taken into account. Maintaining a crop sensor camera system could be a more cost effective choice. Adding a new lens, or upgrading an older one, may see a greater net gain in performance than moving to a full frame camera.

Keep in mind that a new line of higher end crop sensor cameras is likely to be released within the next year. Those new cameras may offer the performance increase, and features that many users of older cameras need, without having to switch formats.

At the end of the day only you can decide whether or not full frame cameras are right for you, but I hope this series has been helpful as you try to make a choice one way or the other.

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