FULL FRAME VS CROP FRAME
Is It Worth The Extra Cost?
For me the most frustrating thing about trying to determine the differences in Full Frame DSLR images compared to Crop Frame DSLR images, is the fact that most comparisons and reviews seem to focus on the attributes of exposure and color balance and basically settings that can be altered to create a different result. But what has always captured my interest has been the field of view and the actual pixel & image quality of the images at 100% size. And even more important to me is how the pixels look at 300% actual size!

Not only did I set out to discover the differences between the Full Frame (FX) and Crop Frame (DX) cameras, but also the difference in a 14Mp DX and the massive 24Mp DX camera.

I personally don't care for the term "Crop Frame" as it makes it sound like you are getting less of an image. While indeed you are getting less, it is more like the difference between the size of the negative as in 135 mm film compared to 126 film. You are not really getting less picture, but rather the sensor (negative size) is smaller. The amount of pixels could be more closely related to the "grain" of film than the sensor size. But then again, not actually, it is indeed a confusing bit of numbers now used in photography. As the ISO (ASA) of the sensor/film increases so does the graininess or "noise" as it is called in the digital camera image.

Does Size Really Matter?
The cameras in this project used are:
Nikon D600
Effective Pixels: 24.3 million
Sensor Size: 35.9 mm x 24.0 mm
RAW Image Size: 6016 x 4016
Nikon D7100
Effective Pixels: 24.1 million
Sensor Size: 23.5 mm x 15.6 mm
RAW Image Size: 6000 x 4000
Nikon D3100
Effective Pixels: 14.2 million
Sensor Size: 23.1 mm x 15.4 mm
RAW Image Size: 4608 x 3072

The image size of 135mm film is 36 x 24 mm, which means that the full frame camera in this experiment is almost exactly the same size. You can also see that the sensor size of the D7100 and the D3100 are almost identical but with the D7100 producing an additional 10 million pixels. As such, in comparison to film, those numbers would say that the D7100 has less grain/noise than the D3100. As where the D600 sensor would theoretically compare to being a larger film size than the DX cameras. Much like how the difference between 135 film was compared to 120 film.

And so there you have it... the whole reason of my curiosity to be answered. I really just want to see the pixels and their quality compared to each other.

The Basic Set-up
To keep the comparisons as close as possible without trying to be exact or scientific, since this is actual real world test and not some kind of lab set up that yield results that never come into play during typical use of the camera. And most importantly to let you visually see the difference and not in a bunch of fancy charts and graphs.

The cameras were on a tripod and shot one after the other while leaving the tripod in the same place and just using the same removable tripod base on all three cameras. While there may be some slight differences in exactly where the tripod base is on the bottom of the camera you can still see form the resulting images what the visible differences are. The in camera sharpening was turned off and no sharpening applied in processing. The in camera color space used was Adobe RGB. Also note that all images were opened with Adobe Camera RAW into Photoshop with default settings with no adjustments to sharpness, color balance, chromatic aberration or any other adjustments that could refine the outcome of the image.

The first examples are using a wide angle lens as in the case with the D600 it is a 24mm and 18mm on the DX cameras. These examples also point out another fact that it seems so many photographers don't realize...

The focal length of a lens is not some standard measurement as to how wide or close up it will make the image seem. But rather, the focal length is the distance from the optical center (the point where light rays converge to form a sharp image of an object) of the lens from the sensor/film. You will notice in these examples that not only is the sensor wider in the FX camera but the sensor is even slightly further back from the lens mount. As you can see the 24mm FX captures an even wider view than the 18mm DX, and if I was to use the 18mm (a quite expensive lens) on the FX camera, that it would even capture a far greater width of the scene.

The FX image captured from the same exact spot the DX images were captured gives you an idea of the differences between the focal length numbers that are not really any type of industry standard in terms of how wide they capture. It seems to me that the 28mm on a FX camera would be more similar to the field of view I am getting with the 18mm on the DX cameras. Also note that these captures were made using also a matching FX or DX lens depending on the camera body.

Due to the slight difference in the tripod socket on the DX cameras you see a very minimal difference, but it is mainly only in the composition and not the field of view. Both cameras seem to capture identical fields of view. I also purposely captured these images at very high ISO so that I could use an aperture of f/16 so that all 3 cameras would produce a image with quite a bit of depth-of-field. I also chose a fast shutter speed to keep elements in the scene from blurring due to wind or movements.

The Long Shot
In the following set of images, they were captured with a FX format 70-300mm... this is where the "crop factor" comes into the scene. As it is stated by most camera manufacturers that the FX lens on a DX body will give you a magnification ratio of 1.5, and thus the image appears as if you "cropped" a full frame image.
You can see that the final result of the D600 and D7100 image are almost exactly the same size when it comes time to print. The confusing issue amongst the whole FX vs DX is that the sensor's pixel size is different and not actually the size of the file formated pixel you see in Photoshop or Lightroom. As you can see from these specs, the FX sensors pixel size is larger, but this is not the pixel size produced from the actual formated image. Sensor Pixel Size: D600 - 5.96µ / D7100 - 3.91µ

In the end... 6000 pixels is 6000 pixels when viewed on the computer screen at the same amount of pixels per inch (PPI). The difference in the sensor pixel size is comparable to the difference in 35mm and medium format with both negatives being printed to a 13x20 print. The FX has a bigger pixel that it captures with and thus when converted into a formatted image it required less enlargement to get the same size image as the smaller sensor did. But... the formatted image is not built using those same differences in sensor pixel size and thus you end up with a 13x20 print from both the FX and the DX. each with about the same amount of pixels from images at 300 PPI.
As you can see that the actual micron size of the camera sensor varies from camera to camera, the actual size of the pixel in the resulting image captures are the same. Yes, I know this makes it seem all so frigging confusing, but this didn't really become such an issue until Nikon put a 24Mp DX format sensor in a camera. As confusing as it is seems, both the FX and DX cameras produce the same size final image it is just that the pixels the sensor captures the image with are of different sizes. So in fact you have 2 type of pixel sizes. One for the size of the sensor and another for the size of the output.

If you are quite observant and noticed that unlike the wide angle comparison where I used matching FX lens and DX depending on the camera type... In these examples all three were captured with the FX lens, not only to show you the "magnification" difference when using an FX lens on a DX camera but I also discovered a very confusing fact in this test.

I also had the 55-300mm DX lens available to shoot with and to my surprise there was no difference in the magnification when used on the DX cameras compared to the FX 70-300mm lens used on the DX cameras. This fact really had me and my assistant scratching our heads, as according to the numbers and data published, it seems as if the 300mm DX lens would not have the same magnification as the 300mm FX lens. But in fact both lens gave the results of a 450mm would on a DX camera. Since camera manufacturers had produced a special DX line of available lenses, and specifically to compare to their FX counterparts, it is obvious the neither the wide angle or the telephoto are in direct proportions to each other as you are led to believe.

Getting Up Close
While I was able to predict the results i saw with the wide angle comparison, the telephoto comparison really threw me off when using the DX 300mm on the DX camera that produced results almost identical to the 300FX lens on a DX camera. So then I set my sights on the results with a macro lens.

At this point in the study, results with the D3100 were not as important to me after being baffled by the results from the 300mm lens. And at such a close distance from the subject, the difference in the tripod socket location became more apparent in the D3100 compared to the others.
Since I didn't have a 60mm DX macro lens to test and the 80mm macro DX lens available produced about the same results in field of view as the 60mm FX lens did on the DX cameras, I didn't bother to post images that were almost identical. My biggest interest actually in this whole experiment was basically the results from a 24mp FX camera compared to a 24mp DX camera since the pixel count is almost the same but the sensor size is not.

If you really like shooting macro and getting as close as possible, then certainly the DX camera body will get you there. And on the other end of the spectrum, the magnification factor makes the DX camera reach further to grab those telephoto shots. So then why even bother with full frame? For that answer let look close at those pixels and see if it's worth it or not. Especially since a FX body cost a bit more than a DX body and most FX glass cost more than DX glass.

Show Me The Pixels
As they say... "The Proof Is In The Pudding", it is already evident here at a 100% magnification of the image. Since the D3100 image is 1400 pixels shorter in length and almost 1000 shorter in height, I expected to see more noise/grain than the other 2 cameras. And while the D7100 produces an image only 16 pixels shorter in each direction, I was thinking they would be pretty close in the amount of noise at ISO 1250. But you can see that the D600 image does produce an image of the least amount of noise, and as a result yields a bit sharper image.
You can also notice on the edge of the "T" in the word "Last" on the sign that the D7100 shows a bit more chromatic aberration, but this also slightly may be since the lens on the D600 and the D3100 are more costly ED versions with more "Extra Dispersion" glass to combat those aberrations, whereas the lens on the D7100 is the "kit" lens that comes with the camera. You can also notice the aberrations along the edge of the passenger container on the Ferris wheel. But yet, it has been my experience that even the more costly "ED" lens is quite capable of being the victim of chromatic aberrations.

You can also easily see the difference in noise levels shown in the glass of the passenger compartments of the Ferris wheel. With the D3100 being the leader in the amount of noise... but thats something you don't really want to be a leader in.
When examining the same images taken at 24mm at ISO 400, you can see that all three cameras show some aberrations along the right edge of the dogs face, with the D7100 exhibiting slightly more than the others. You can also see the the DX cameras show a slight bit more noise in the sky background than the FX camera does.

As in the previous examples at ISO 1250/1600, you also will notice that the D3100 image is of less magnification since at 100% the image is 1400/1000 pixels smaller than the others.

In a closer examination of similar magnifications of the scene (using the same lens on all 3 cameras @ ISO 400) at 100% pixel size you can see most definitely that the D3100 is the softest of all three. The D3100 also shows almost as much aberration as the D7100 along the left edges of the sign, thus disproving the fact that lens manufacturers say the extra dispersion glass eliminates more aberrations than the lower price glass.
Although it is irrelevant to the purpose of this experiment for me, I am seeing that the D7100 has a slight bit more cyan/blue color cast in the highlights that the other two, even though all three cameras were set to use the Adobe RGB color space. A slight modification to the color space could clear that issue up as discussed on the TPE FaceBook page.

As for overall sharpness, the actual difference between the D600 and D7100 is very minimal if any in this example. And even in the previous example at the wide angle setting, the two cameras are very similar in overall sharpness with the D7100 shown just a slight bit more noise.

There is also a noticeable difference in the richness and color rendition between the FX and DX cameras, although it could be adjusted in Light Room or Photoshop, I was interested to see that the FX images had a slightly deeper/richer look top them in some images but not necessarily all of them.

Before looking over the next set of images, keep in mind that this experiment was purely to determine the difference in field of view and the actual sharpness and noise of pixels when viewed at 100%. As these result so far have shown that in normal picture taking with focal lengths between 40-80 mm that the differences in these cameras will probably be almost not visible unless they were printed to a size of 16x24 or bigger.

Since I print a large portion of my works at sizes bigger than 13x20, I was most interested in just how good the pixel quality was in these cameras. Obviously you could print 5x7's from each of these and most likely not be able to tell a difference in most cases. Or at least until you start shooting with a macro lens.
With a prime macro lens, even at f/16 the depth of field is very shallow, remember that these test were for the quick grab-the-shot situation. You could in fact boost the ISO and get the lens stopped down to f/32 and get some sharper results. But in this case, these shots were on a typical "walk-about" type shoot and special macro preparations were not made to seek the sharpest image possible. With that in mind, I can see that still the Full Frame camera seems to finally rise above the others a little bit more even though due to the crop/magnification factor the DX format with an FX lens will get in closer.

I also noticed on the macro shots that the D3100 seemed to introduce a little bit more saturation than it did in the other shots. There again that is an issue adjustable in Light Room or Photoshop. Yet, in this quick shot example, it does seem the the D3100 is about as sharp as the D7100 in macro situations. Or should I say... in this macro situation.

Going Beyond...
In the following examples you can see the results of how the pixels look when viewed at 300% magnification. This is probably where you can really begin to see the differences in what the larger sensor can do for you even though the D600 and D7100 have almost the same amount of pixels.

Those noisy pixels are really there, but you just don't see them till you look closer than just at 100% magnification. You can see that the D7100 introduces some unpleasant noise, especially in the red color of the sign. And we won't even begin to mention the splotches of dark noise in the D3100 example, particularly since the pixel count is much less than the others. At this point, there is no comparison between 14Mp and 24Mp DX format cameras.
Of course these examples above are at high ISO settings, and that is where noise is going to be more evident amongst different sensor sizes and pixel counts. Yet, we are also becoming more accustom to wanting those high ISO capabilities in cameras today which enable us to capture images that are not possible to capture hand held with film. As a result, each new upgrade of a DSLR seems to always improve the noise at high ISO settings as being one of the most talked about new features.

I wish to also repeat my original reasons for this comparison of FX vs DX cameras...
First, was the difference in Filed of View, by which we can clearly see that the FX camera has a wider field of view with a 24mm lens than the DX camera does with a 18mm lens. And due to the crop factor when using a FX telephoto lens, you can clearly see where the DX format camera produces an image from a 300mm FX lens that appears to be more like a 450mm lens.

Although I am still baffled as to the results from the DX 300mm lens on a DX camera that still produce results similar to the FX 300mm lens, my overall interest was simply in the Field of View.

Second, was my desire to actually see the pixel and image quality of the same section of a scene when viewed at 100% and then as you can see in this next round of examples I pushed the ISO 400 captures to a magnification of 300%
Keep in mind of course the sample images may be at different magnifications of the scene, but the study is for how well the sensor was recording those pixels and how "clean" they were as well as for how smoothly they went along with the color change pixels beside them. The above images were also capture with the same lens at ISO 400 viewed at 300%. I must say that I am a bit surprised in the results from the D7100 based on how things use to be with film.

If the film has smaller and more grains in it, it was called a "fine grain film" and produced a sharper image. And as in the D7100, since the sensor is smaller, as a result it crams 24 million pixels into a smaller space, thus they would have to be smaller like in a fine grain film. With the FX sensor being also 24 million pixels, then each pixel would be larger and seems like there would less pixels available to make the transition from pixel color to pixel color.

While there seems to be just a little more noise in the DX sensors, it is the chromatic aberrations that you may not ever notice unless you magnify the image well past 100%. Since both the D600 and D7100 image at 100% when printed at 300 PPI comes out to be a 13x20 print, you may never encounter visibly seeing such aberrations.

But... Back The Question
Is it worth the extra cost to go with FX format?
Of course aside from the issue of cost, one should also add their personal requirements from a camera in the equation. If most of your images are going to be printed that is a consideration that plays into the decision much more than if you always are using your image only on computer and TV screens.

Even the 14Mp image from the D3100 at 100% is a 10 x 15 print, and a very sharp one at that. But when you reach beyond the areas of 100%, such as if you print at 20x30 or larger, then you will see the differences a little more, but I will admit you will have to look closely. I have quite a few 20x30 prints in galleries that were captured on a 12 Mp vintage DX format Nikon D2x, and unless you would know how close to examine the print, you possibly may not be able to tell the difference in a 20x30 print from the FX format D600.

It is often like when I see a spot in a print from some dust or some other error in the process, and I show that print to an audience of people without pointing out the bad spot, very few if any will notice it. Or like the analogy that, if you never drove a Cadillac, then you wouldn't know the difference from the ride of a Pinto. That is, until you rode in the Cadillac and then got back in the Pinto, from that point it would be glaring in your face what the difference would be.

The D7100 handles like a big camera, has a fast shutter response and produces a hell-of-a image that could be enhanced or repaired in Light Room or Photoshop to produce masterful works. The deciding factors in going to Full Frame would need to be, how big are you going to print and how often are you going to want clean images at high ISO's like 3200 or 6400. And even though both the D600 and D7100 will go up to ISO 25,600, you certainly will not get clean gallery quality images at those speeds.

If the price difference of a D7100 @ $999 and a D610 @ $1,499 doesn't bother you... then make sure the cost of glass is factored in as well. Since a DX format 16-85 mm lens is $699 and a similar speed FX 24-85 mm lens sells for $599, you really can't go by the common statement I hear all the time that "FX glass cost a lot more". Yes, most of it does cost more, but there are enough comparable lens available at similar price points.

You can find some similar lens between the two formats in the same price, but the variety is not the same. You will also find a greater variety of faster, higher quality lens for the FX cameras... of course at a hefty price.

Do It Again?
After scrolling through the images from these three cameras, looking at them at various magnifications and being rather critical about the quality of one pixel next to the other... and you were to ask me if I had a "do-over".

"Would I still buy the FX camera over the full frame" back when I bought mine... Hell Yes, I would.

But keep in mind, that is based purely on the presentation and printing requirements I have from my images.

If I never needed large format output and mostly kept everything on the computer or just small prints, then there wouldn't be much need for me to go Full Frame.

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