Independence of irrelevant alternatives

by Chris Bertram on March 7, 2007

So I’m contemplating buying a digital SLR, and, after much huffing, puffing and reading of reviews I’m hesitating between a Nikon D40 and Canon EOS 400D (or Digital Rebel XTi as they call it in the US). The Nikon has a six megapixel sensor and the Canon has ten, and the Canon has some patented dust-removal system. But the Canon costs £100 more. I figure the extra isn’t worth it, and, ten days ago, I buy the Nikon. A couple of days ago Nikon announce a new camera, the D40x. Same as the D40 (more or less) but with a 10MP sensor and an expected price-tag that matches or exceeds the Canon. The comment boards go nuts with discontented D40 buyers, and I think — for a moment — “I should have bought the Canon.” Reminds me of the Sidney Morgenbesser joke:

bq. After finishing dinner, Sidney Morgenbesser decides to order dessert. The waitress tells him he has two choices: apple pie and blueberry pie. Sidney orders the apple pie. After a few minutes the waitress returns and says that they also have cherry pie at which point Morgenbesser says “In that case I’ll have the blueberry pie.”



Michael Greinecker 03.07.07 at 11:57 am



Richard 03.07.07 at 12:58 pm

so how do you like the Nikon?
I’m facing exactly the same choice, except I’m considering the Canon 350 (rebel xt).


Matt 03.07.07 at 1:27 pm

If the sensor on the D40x has twice the area of the old sensor, you’d have some cause to be upset. Otherwise, [insert rude noise].


Chris Bertram 03.07.07 at 1:53 pm

richard – I like the Nikon just fine. Easy to use, does what I want it to. But I’m still learning … I expect the Canon would have done just as well though.


swampcracker 03.07.07 at 1:53 pm

Richard (12:58), Canon would be the better choice … Nikon sensors have a tendency to be noisy, prone to dust (static electricity), energy hoggish.


eudoxis 03.07.07 at 2:16 pm

But the Nikon D40X is considerably more expensive than the 40D and you’ve already made the decision to pass on the far superior Canon 400D (comparable more to the Nikon D80 than the D40) for a smaller price difference. Make up for all that buyers remorse with a few good lenses and you’ll be happy.


abb1 03.07.07 at 2:23 pm

Why would one need a 10mp sensor; isn’t this kind of resolution necessary only if you’re planning to print wall-posters? Shouldn’t a 6mp sensor be enough for almost everything else?


raj 03.07.07 at 2:53 pm

The number of megapixels is less important than you might believe. The image recorded by the sensor is usually stored in compressed format, and the compression algorithms that are used probably determine the clarity of the photos. Storing the image in raw format would probably overwhelm the storage media, particularly for a 10 megapixel camera.

If we get a digital SLR, it will probably be a Pentax, but that’s because we have some older Pentax auto-focus lenses that we bought for film cameras, that can be used with Pentax digital SLRs. If you have Nikon or Canon lenses used with earlier cameras, you might want to factor that issue into your decision.


clint 03.07.07 at 3:22 pm

Abb1 is right on. I’ve printed posters from of my Nikon D50 (6mp but uncropped photos) w/out any resolution problem.

Nikon is, intelligently, charging a huge mark-up for a feature lots of folks want but almost no one will ever use.

I’ll second the person who suggested taking your savings and expanding your collection of lenses, they’ll expand your range of photo options (and improve your quality) in a way extra mps can’t.


almostinfamous 03.07.07 at 4:28 pm

i’d say d40 all the way.

it’s lightweight(even with kit lens), and shoots pretty quickly. it also has a gorgeous screen with a nice display that tells you what the aperture and shutter speed and other photographic mumbo-jumbo do.

the interface on the 300/350D never really appealed to me, but i hear the 400D is a bit better, though for me,not worth the price.


almostinfamous 03.07.07 at 4:30 pm

say = take… it’s been a long day.


rm 03.07.07 at 4:30 pm

The Canon was the better choice just because it’s a Canon, the way a Toyota is always a better choice than a Chevrolet.

But eudoxis is right at #6: if you had already chosen the Nikon for the price, the existence of a high-priced Nikon shouldn’t change anything.

Now, if you had chosen between two Nikons, and then Canon came along with a new alternative, then you could slap your forehead a little for not waiting. But you’d still be better off than if you had chosen the high-priced Nikon.


abb1 03.07.07 at 5:27 pm

There’s another little paradox here: if you wait for a newer better model about to be announced, you’ll never have any camera at all.


Andrew Brown 03.07.07 at 5:38 pm

raj, If you have Pentax lenses, the Pentax DSLRs are excellent. I don’t suppose there is all that much difference between any of the top brands. There are, however, an awful lot of cheap, good, second-hand Pentax lenses to be had these days.


alkali 03.07.07 at 5:42 pm

12: But eudoxis is right at #6: if you had already chosen the Nikon for the price, the existence of a high-priced Nikon shouldn’t change anything.

I think this is wrong.

To restate the problem, the choice is between N and the £100-more-expensive C+ (where the “+” reflects the feature that N doesn’t have). The buyer is uncertain about how to evaluate the value of the feature. (By way of comparison, if he were a professional who knew that he could get X additional jobs that would bring in Y amount of money if he bought the camera with the additional feature, he could place a value on it. But he’s not.)

The buyer could reason as follows: “The C company thinks that buyers like me will value the feature at £100. Accordingly, if I would place less value on the feature than the average buyer, I shouldn’t pay £100 for the feature; if I would place more value on the feature than the average buyer, then I am getting consumer surplus by buying for £100.”

If the buyer were to learn that a new camera N+ is priced at (say) £200 more than N, that might suggest that the feature ought to be worth more than £100 to the average buyer, and the buyer might alter his calculus accordingly.


blueshoe 03.07.07 at 5:54 pm

The finely opinionated Ken Rockwell writes:

“The D40x was announced yesterday, March 5, 2007. It’s the same as the D40 with a few more pixels, a slightly faster frame rate and a whopping 33% price increase.

“I’d pass on the D40x and get a D40 instead. They are the same camera, and the D40x costs much more for no significant change in quality or performance.

“Nikon probably added these needless pixels to the D40x to compete with the Canon Rebel XTi on banner specifications that impress innocent people, but do nothing to improve the pictures or usability….”


astrongmaybe 03.07.07 at 6:02 pm

I don’t know anything about cameras, but… “Digital Rebel XTi” is the lamest name I’ve heard in a very long time.


Western Dave 03.07.07 at 6:07 pm

omment 15:
“If the buyer were to learn that a new camera N+ is priced at (say) £200 more than N, that might suggest that the feature ought to be worth more than £100… ”

Or that people are suckers. Given the choice between rational choice and P.T. Barnum, I’ll choose Barnum every time.


CJColucci 03.07.07 at 6:07 pm

What do people think about the Olympus digital SLRs? I have used an OM-1 (film) SLR for nearly 30 years with no complaints, but I’m thinking of taking the digital plunge.


novakant 03.07.07 at 6:41 pm

Ken Rockwell is very opinionated indeed, especially when it comes to Megapixels. And while some of his points are well taken and there are many other important factors that have to be considered when buying a camera, it’s not true that more pixels are useless. As always, it depends on the planned usage: to cut a long story short, if you’re going to do a lot of post work you will notice quite a difference, if not, not so much. Also, in the age of 4-8 Gig memory cards, storage becomes less of a problem.


Justin 03.07.07 at 7:26 pm

Why would one need a 10mp sensor; isn’t this kind of resolution necessary only if you’re planning to print wall-posters? Shouldn’t a 6mp sensor be enough for almost everything else?

Shoot wide, then crop. This is the hallmark amateurs who take candids.


eudoxis 03.07.07 at 8:00 pm

To restate the problem, the choice is between N and the £100-more-expensive C+ (where the “+” reflects the feature that N doesn’t have).

No, that’s not a restatement of the problem. The difference between the Nikon D40 and the Canon 400D are multiple. The feature that Chris is suddenly interested in, the 10 MPS, is present on the 400D, for a price increase that is less than the price increase for the new Nikon D40X. Plus, the Canon has a better sensor. They’re just different cameras and not really in a comparable class. Then, it has a dust-removal system which, if it works, is a lovely thing to have on a D-SLR.


cormac 03.07.07 at 8:33 pm

The image is made up of three things –

(1)lens quality -> controls input to the sensor
(2)sensor fidelity->controls what is output from the sensor
(3)compression algorithm -> controls how accurately sensor output is stored

For (1), Nikon is better than Canon. Nikon lenses are superb.

(2) is determined by MP and quality of sensor. The MP controls only resolution – how much of detail is stored. There are only a few manufactures of CCDs.
(3) how lossy is the compression has much more of an influence than MP.

Given the same quality of sensor, lens and compression algorithm has more to do with picture quality than MP.
(3) is


Chris Bertram 03.07.07 at 8:48 pm

The tribal/technical thing is very interesting. But the post was really about catching oneself in a bit of irrational thinking. (I’m perfectly happy to live with what I’ve bought.)


Joel Turnipseed 03.07.07 at 9:30 pm

As I pass into my second year with my D70s, I feel like someone should point out that all the lenses and megapixels in the world don’t matter the slightest w/r/t good pictures, on two accounts:

1) There’s the obvious matter of usual ideas of composition, understanding of technical details (aperture settings, etc.), and so on–these all go under bundle of “it’s the photographer, stupid.”

2) More importantly–never underestimate the difficulty of getting a good, clear shot. Even with the VR (vibration reduction) lenses, it’s all-too-easy to move just that tiny, tiny little bit while clicking the shutter and thus introduce an element of blur that dwarfs by far anything you’d get by, say, enlarging the photo in Photoshop (or another way: more megapixels just means bigger, not clearer, picture in many cases).


Errol 03.07.07 at 9:59 pm

all the lenses and megapixels in the world don’t matter the slightest
That over-states your point. Appropriate equipment makes it easier for a skilled user to take better photos. Expensive and fancy is not appropriate for most.
Regarding your (2), always taking a burst of 2 or 3 helps counter this somewhat.


alkali 03.07.07 at 11:55 pm

eudoxis (#22) writes: No, that’s not a restatement of the problem. The difference between the Nikon D40 and the Canon 400D are multiple.

I appreciate that I simplified the facts. The idea is that the price of a new camera is new information that a buyer could use to infer something about the value of another camera’s features.

To put it in terms of the apple/cherry/blueberry pie joke, suppose you prefer fresh apple pie to any kind of blueberry pie, and you prefer any kind of blueberry pie to apple pie that’s been sitting around. If you know that the restaurant serves only apple and blueberry, you might infer that the pie turns over pretty quickly and so you’ll take a chance on the apple. If you learn that the restaurant also serves cherry, you might decide that the apple pie is less likely to turn over (no pun intended) and choose the blueberry.

The point is that new information can be put to use in surprising and counterintuitive ways.


dsquared 03.08.07 at 12:56 am

There’s another little paradox here: if you wait for a newer better model about to be announced, you’ll never have any camera at all.

And of course lots of people do in fact refuse to buy things exactly for this reason, which is why the behavioural crowd think that this vN/M axiom might be a bit weaker than it is normally thought.


radek 03.08.07 at 1:18 am

Re 13 and 28. Actually it can be set up as a well defined optimal waiting period problem if some conditions are met. Basically there needs to be restrictions on growth rate of quality and the path of prices and the discount rate. It’s sort of like in the Ramsey model the discount rate has to be high enough relative to the growth rate of income (times that stinkin’ eta) or else you want to consume everything at infinity.


DILBERT DOGBERT 03.08.07 at 1:19 am
Or Google Philip Greenspun. MIT computer geek with a photo habit. Very full of himself but fun anyway.
He likes Canon.
Also go the NYT tech guy he just had a post on the megapixels race and sensor size. He also had a review of a zoom lens he liked. It had image stabilization built in and he liked it.
Read and confuse the hell out of yourself then go buy what ever that takes your fancy. I shoot mostly for the web as I like the free distribution possibilities of Snapfish and Shutterfly. I use a little moby 3.2MP Exilim EX-z30 from Casio. Works great except it has a mind of its own and likes to start shooting movies without being asked. Annoying but once you know of this bug you are alert and fix it before you do a lot of movies of the sky and ground with sounds of a very puzzled cameraman in the background.
I like the small pocket cameras cause I then have them for those special moments that flyby while you are getting out the big camera and fitting the just right lens.
Get a copy of Photoshop and learn how to use it to fix you bad photos. The Curves tool is a wonder at brightening dark photos and darkening the overexposed light ones.
If you are a serious camera geek then get the big SLR and an off camera flash. If you like the deer in the headlights look then go with the on-body flash.


vivian 03.08.07 at 1:47 am

Chris – it is amusing that you found a real-life Morgenbesser-like example. But did you buy the camera to keep up with Ezster’s Flickr challenge? How will your new camera affect your posts here – illustrations? fewer, since you’ll have a new hobby? A change in the music/visual art ratio?

fwiw, I love the D50 nowadays – it has remarkably little noise, almost no shutter lag, enormous battery life and such. Does anyone know whether Morgenbesser actually had an antecedent prefered flavor of pie? (economists would just poll the patrons and choose the (a la) mode, but philosophers have to be more principled, right?)


watson aname 03.08.07 at 2:14 am

I think the Canon vs. Nikon thing here is misleading. Basically, Canon doesn’t offer a direct competitor to the D40 … but neither does anyone else, really. Nikon has bracketed the low-to midlevel offerings of Canon this way (there isn’t a Canon to directly match up with the D200, either). So you are choosing to enter the market with a Nikon that doesn’t (yet) have any direct competition.

I think the existence of the D40x muddies the mid to upper entry level stuff a bit for you, but doesn’t change much. The D40 is in a class of it’s own, it’s small, lightweight, and quite capable. It has some limited lens compatability, but that probably doesn’t matter to you.

It’s the lenses that really matter. If you stay at this long enough and get interested enough, you’ll build up a bag full of lenses that will make it difficult to change mounts. But this is as it should be; glass is more important that bodies. Less so now that with film, but still true.

by the way rm is quite confused with the Toyota vs. Chevy comparison — Nikon dominates (technically, not in unit sales — yet(?)) the middle range of DSLR’s. Sure, there are trade offs, but the D200 is a much better camera than the 30D, and a better sensor with one caveat — high ISO shooting.


derrida derider 03.08.07 at 2:25 am

You get more megapixels to let you crop. You don’t have to worry about composition when shooting, and you can mostly get away without a bulky long lens.

But yeah, most buyers overestimate the importance of bulk MPs compared with other things.


Harald K 03.08.07 at 7:10 am

Chris Bertram, that was not necessarily just irrational thinking!! So Arrow’s theorem says there can be found no social choice funcion which satisfies blah blah criteria, unless it is a constituency of one. Who says you’re just one?! You probably have lots of different reasons for wanting to buy a camrea, and look, now they’re locked up in a CYCLE!! Woot!


maidhc 03.08.07 at 9:20 am

More megapixels don’t necessarily “let you crop”. If the resolution of the sensor is greater than that of the lens, cropping is like using that useless “digital zoom” feature. It just increases the relative size of the blur.

If you read a lot of photography sites you’ll find people arguing that 10 megapixel sensors don’t give any better resolution than 6 megapixels if you have consumer-quality lenses.

35 mm film has more resolution than any current digital sensor, but the results you get with film will still vary according to the quality of the optics in your camera.

Digital gives you the advantage that it doesn’t cost anything to take a lot of different shots, so you can try a lot of things like framing, depth of field and exposure at the time when you shoot, and pick the best result when you get home. You don’t necessarily have to spend a lot of time adjusting the picture later, although you still can.

I bought a Pentax digital SLR because I already had Pentax lenses from my film camera, and I’ve been very happy with it. But I imagine that all of the well-known companies probably have pretty decent products.


radek 03.08.07 at 10:06 pm

unless it is a constituency of one

Or two. Sorry for being pedantic.


Peter 03.08.07 at 11:47 pm

I disagree that violation of the IIA Assumption is evidence of irrationality. Surely, it is rational to consider context when making decisions, yet the IIA Assumption asserts that context is ignored — like so much of western thought since Descartes.


radek 03.09.07 at 12:58 am

Peter, I think the key is the word “Irrelevant” in Independence of Irrelevant Alternatives. Relevant context is fine. In a broader sense though you’re right, as the famous blue bus/red bus illustrates.


eweininger 03.09.07 at 3:24 am

Aw crap. I was gonna make some joke about needing the Nikon on the red bus and the Canon on the blue bus. Oh well.


zdenek v 03.10.07 at 2:03 pm

“I should have bought the Canon”

This is correct I am afraid because CCD sensors that Nikon uses are prone to premature failure ( the sensor outputs just noise or goes completely dead , of course it can be replaced but will cost half the price of the new camera ).Until this is sorted out by the manufacturers of CCD sensors CMOS type sensor Canon uses I am afraid is better bet.


Randy Paul 03.11.07 at 3:30 am

The only area where I would give Nikon the edge is with the lenses, but IMHO, it’s not a great enough difference not to get the Canon.

I have a Canon Digital Rebel XT and the fact that I had some Canon lenses (22-55mm zoom; 75-300 mm zoom) sealed the deal for me. I also have a Canon APS SLR (though I don’t really use it any more) and I took some terrific photos with it.

I just got back from 2 weeks in Italy, took some 600 photos and was very impressed with how it hheld up. I only had to recharge the battery once in two weeks.


Randy Paul 03.11.07 at 3:34 am

The only thinng I might add is that the software package that comes with the Canon is very impressive and easy to use.


zdenek v 03.11.07 at 10:10 am

Another point in favour of Canon is the fact that Canon auotofocus motor is inside the lens and not the body.

As lenses develop the motors become ever more fast ( even the ultrasonic lenses are becoming faster ) so when you upgrade you may be buying a lot quicker focusing lens than the one with which you started.
Because Nikon put their motor inside the body no matter what lens you buy you will be stuck with the same auto focus performance unless you upgrade the body too.


Chris Bertram 03.11.07 at 12:22 pm

Zdenek, what you say simply re autofocus motors simply isn’t true. The D40 has no af motor in the body, only in the lens. (This is often portrayed as a _disadvantage_ of the camera to those with old Nikon lenses.)


zdenek v 03.11.07 at 12:43 pm

Yes I forgot we were talking about D40. But notice still on this subject , none of the fantastic older Nikon lenses that could otherwise be used with your D40 body — say the fantastic 80-200 F2.8 — ( fast and not expensive ) cannot be used because your camera will not focus with them ( no internal AF motor ).
This is quite a draw back I think.


zdenek v 03.11.07 at 1:04 pm

I think D40 is a fantastic camera but this issue with lenses can be important.

If you bought Canon 400D you might want to upgrade by buying a fantastic relatively inexpensive Canon 100-400 F4-4.5 whic comes with ultrasonic motor and image stabilizer. This lens has some of the key lens elements made from fluoride.

It is a lens used by lot of profesionals and as I said prices have gone down recently and so is accessible to serious amateur.

Something similar from Nikon will not work with your camera because of this AF motor issue.

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