Sunday, October 30, 2011

Fuji X10 Versus Nikon D5100 / D7000 – who has depth of field supremacy … *Updated* for the 18-55 kit lens as well … *Updated* again for a different 2/3” sensor …

Fuji’s X10 is their newest advanced compact camera, sporting an incredibly fast f/2-f/2.8 lens on a 2/3” sensor. These specifications have everyone in tizzy over the depth of field possibilities. So much so that DPReview’s own preview makes a very bold statement, which I have underlined for your enjoyment.

Bright manual zoom lens

Despite the larger sensor, Fujifilm manages to find room for an image-stabilized, retracting 28-112mm equivalent F2.0-2.8 lens. The wide aperture, combined with large sensor means not only does the X10 offer more control over depth-of-field than any other camera in its class - it also allows for shallower depth of field than most DSLRs when used with their kit zooms.

WOW! Is it possible that a tiny sensor like the X10’s can achieve supremacy over a bog standard and dirt cheap kit lens like Nikon’s ubiquitous 18-105VR? Because that would be an incredible coup for Fuji. This would be a near-ideal on location portrait lens, which would really shake things up I think.

Well … they were actually a little overly enthusiastic and in fact their statement is just plain wrong. In fact, when you compare the X10 against Nikon’s D51200 or D7000 (or any Nikon APS-C sensor, frankly) with the 18-105VR mounted, the Nikon easily defeats the Fuji in every category.

So I have no idea how DPReview could make such an error of unbridled enthusiasm, but I can show you the real numbers. So first we have to pick some criteria (which DPReview failed to mention at all as some form of framework for their statement.) Let’s choose two subject distances at 5 feet and at 15 feet. That ought to be close enough to cover a lot of range of portrait situations at full wide to full telephoto.

Next, we define the categories, which are actually really easy. We’ll shoot at the two extremes at full wide and full tele at both distances. That gives us 8 comparisons over which we can tally the shallowness of the depth of field at wide open and the opposite for fully stopped down, i.e. we are going for more in the image (e.g. to shoot groups) and since subject distance is fairly close, we will determine two sub-categories. If we are shooting wide, we usually want what is in the background fully in focus when we stop down. But when we shoot at full tele, we usually want the background slightly blurred (especially when shooting people.)

I used to handle the calculations, selecting the 2/3” sensor since the X10 is not in there yet. And I selected the D7000 since the D5100 is not in there yet. But in both cases the sensor size is correct and that is what matters.

The Fuji lens is 7mm at the widest with apertures from f/2 to f/11. At tele it is 28mm with apertures from f/2.8 to f/11. The effective range is 28-112.

The Nikon lens is 18mm at the widest with apertures from f/3.5 to f/22. At tele it is 105mm with apertures from f/5.6 to f/36.

From a cursory reading of the apertures it sure looks like the Fuji should do well. And it does. But the Nikon does better, which contradicts the statement in the preview.

I put all the calculations in a small text file, which I will embed here:


The Fuji really does ok for a small sensor. But the 18-105VR is everywhere and it is cheap. So DPReview really stretched the point with that comment. Shooting a kit lens allows great control over depth of field, far more than is available on the tiny sensor.

The major difference is that the dSLR is not limited to the kit lens. It can go much shaller with fairly inexpensive lenses like the 50mm 1.4G or the 35mm 1.8G. And it can go much wider with the Sigma 10-20 or even the Nikon 16-85.

Not to denigrate the X10 in any way. I expect this thing to be fantastic. But don’t subscribe to the fantasy that it is the answer to the cream machine (name for any lens that gives buttery smooth backgrounds) because it is not.

EDIT: A user suggested that the preview probably meant the older, previously ubiquitous 18-55 kit lenses that remain in kits at the low end and with sell outs of older models (as is happening right now at Future Shop) … well, 55mm at f/5.6 sounds like a loser to me. But …


Yeah … still better than the tiny sensor. LOL

EDIT 2: A few people are pushing hard to get the X10 the recognition it deserves. They say that DOFMaster generates the wrong numbers for the 2/3” sensor, but generates the right numbers from cameras with 2/3” sensors (Minolta dImage A1, Sony 717, Sony 828.) So I checked, and indeed the numbers are different and the 2/3” sensor finally eeeks out a narrow victory over the cheapest kit lenses at 55mm and f/5.6. By inches.

Of course, we don’t really know who is right, but some are offering to “show me the math” so one presumes that they at least believe the new numbers. So let’s see them:


So … what to conclude? Well, all those people who buy the cheapest 18-55-based kit on Nikon will have slightly less subject isolation at the long end wide open than the X10. That appears to be true (at least, on some settings of DOFMaster.) But if you buy the newer and much better 18-105 (not that much more expensive), you still get better subject isolation, and by a bigger margin.

So the comment made in the preview has some merit when you take into account that the cheapest entry-level dSLR kits are what the masses like to buy at COSTCO and Best Buy. I’m not really favorable to such writing, as equivocation can be used to untangle some of the many variables involved. And, of course, the fact that DOFMaster has two different sets of results is a bummer :-)