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Tuesday, 26 September 2023


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Wouldn’t square millimeters (area) be the best designation? Easy to compare and easy to understand. I suppose that is why the marketing types have avoided it.

"...format that suffers in this nomenclature is Four-Thirds, because it has a 3:4 aspect..."

Maybe the single number could be the 4 sides of what ever the aspect ratio is added up. Full frame would be 120, Nikon APS-C would be 84, etc.

DPR says the iPhone 15 sensor is 9.8mm on the long edge. I just ordered the pro max, and am looking forward to it.


As regards Four Thirds (and presumably micro 4/3), the spec is defined by the 4/3" (in video camera terminology) of the image circle, and manufacturers could use different aspect ratios. Thus, the maximum number of pixels in a 4/3 compatible camera would be realized in a square sensor since it would maximize the area of an image sensor (for any given pixel density).

As a side note, I recall reading when the Olympus E-1 came out in an interview with senior Olympus executives their belief that they thought the format would be technically viable to an upper limit of 20 megapixels. I don't think anyone has released a higher pixel count camera in 4/3 or micro 4/3 to date.

Also, I would love a square aspect ratio camera and would probably buy if it weren't too dear.


I prefer the 4:3 aspect ratio. It's one of the reasons I got a GFX camera. 3:2 is not very attractive in portrait orientation unless you want to crop the top/bottom. I am one of those weird people who prefers to compose in the viewfinder as opposed to when I print. I also prefer the 4:3 for anything in landscape orientation but that's just me. It's why I always liked 6x6 or 6x7 over 35mm when I was shooting film. I would absolutely love a square sensor camera but nobody is going to make one of those. That is another advantage of the GFX, you can shoot a square photo without cropping the sensor too much. I suppose that's a moot point if you don't print.

Why not just 'area' instead?

With pixel pitch as an appendage in parenthesis.

So micro four thirds would be... hmm... where's that calculator app?

It seems like the obvious way to produce something comparable-ish across aspect ratios while maintaining the proportional relationships between different-sized same-aspect-ratio formats would be to use the square root of the sensor area (or something proportional to the square root of sensor area), no?

I think that in mm that'd give us the following:

1/3" - 4.16
1/1.7" - 6.58
Super 16mm movie - 9.63
1" - 10.8
110 film - 14.9
Four Thirds - 15.0
Canon APS-C - 18.2
Nikon APS-C - ~19.2
"Half Frame" still film (e.g. Olympus Pen) - 20.8
"Full Frame" - ~29.3
Leica S - 36.7
Fuji GFX - 38.1

This reverses the order of Leica vs. Fuji (et al.), near the larger end, though overall they remain very close. It also brings Four Thirds a little proportionally closer to its most direct competitors, although again the change is pretty subtle.

Sometimes real world experience is different. My user experience is that 1” is day and night better than 2/3”, and four-thirds performance is closer to 1” than to APSC. So I would group 1” and 4/3 as the “medium format,” and anything start ing from APSC as “large format” for their applicable user cases.

All of the larger formats have been clear enough to anyone paying much attention. The group you bunch as small sensors have been a black hole which I suspect was the intention from the beginning. The only small sensors I’ve had have been in phones including some that I suspect were even smaller than any in your list.
I would think that a system using diagonal measurements would better reflect the area of the sensor which is what really matters. But you are correct the horse is so far out of the barn it no longer remembers that there was a barn.

Will there be time when sensor form is circle? So camera manufacturers can cut cost on vertical grip and high end sport cameras will be a lot lighter because of lack of it.

Jede Konsequenz führt zum Teufel [a German saying used mostly in The Netherlands, it means "all outcomes lead to the devil," which seems particularly apropos here! —Ed.], but I prefer to use the diagonals for comparing. I would also love to skip all those mysterious confusing interpretations in inches. In other words, just the diameter of the image circle in millimeters please.

And I shoot square which narrows it a bit more and eliminates the vignetting problem in a lot of cases.

I prefer 4/3 and 99% of the time crop the overly long 3/2.

I use a Pana (sorry, Lumix) FZ1000 with a 1" diag. sensor, a Sony RX10 mk1 same, I think, and Olympus OM-D E-M1 mk1 with other E-PL models.

In almost every situation (travel mainly), I choose 16:9. It suits my printing prefs and I like landscapes. And I get nice A4 prints from these. Even A3s.

> But I'll bet not one in 50 photographers (and not one in 5,000 ordinary consumers)

I would claim that this is fine, because it mostly does not matter. And if it does matter to someone they can work it out from fairly available information sources, like this web site. 🙂

I in my time used the phone cameras, APS-C, "full frame" and most recently the 4/3rds cameras.

I mostly don't think about the geometry of the sensor, as the geometry (size/weight) of the camera and lenses are more important to me ... but I also think that there are many more external factors not related to the sensor size that effect what you get in the final picture than factors related directly so sensor size.

I think film size had a more direct effect on "image quality" back in the day because you had to enlarge everything to actually see it. So 120 film (say) looked noticeably different than 35mm Tri-X (yum) because you didn't have to blow up the grain as much. This is not really true in the same way for digital files. Or rather, the story is at least a lot more complicated.

But again, people who care will structure their work to get what they want.

Everyone else will just keep shooting phone pictures.

During 1963 Olympus released the Pen F. It was a half frame film camera that shot 18x24 frames. Therefore you got 72 photos on a roll of film. A good idea that wasn't picked up by others. Too bad because the lenses could be smaller,etc. There are videos on the net of David Bailey using a Pen F.

I'm still saddened that Panasonic didn't make themselves stand out with the S-series by going with a 36x27, 4:3 'fuller-frame' sensor. It would have cost more, but now they are yet another talented player in the 36x24 market.

I think area would be a more useful measure for understanding the size differences. Even more useful is the dimensions of the long and short sides of the rectangle since we could get area, diagonals and aspect ratio out of the pair of numbers.

Totally agree with you Mike. To add to the confusion, DPreview published this article awhile back.

"Making sensor sizes less misleading" - https://www.dpreview.com/articles/4159871805/making-sensor-sizes-less-misleading

At least so far, we don't have digital sensor equivalents of 6x17 medium format (or even 6x9), or any of the other panoramas. But you really should have included 16:9 video format, since that's nearly universal today (including in all our existing cameras and phones).

But I think you're right that we're past the point where this is terribly important. Most sensors are "good enough" for most photographers, and people with special enough needs that that's not true for them need to check specifically what they're buying, since the other electronics around the sensor are also very important these days.

We won't talk about Cinerama!

A very interesting proposal. But for it to have at least a fighting chance, you would have had to drop a decimal from your examples (as in 5.0 instead of 4,98, and 24mm rather than 23,6). Also, a number of sensor properties (light collected, pixel count...) accrue more like the area than the length of the beast. But of course 16 or 200 square millimeters doesn't evoke anything to most people right out of the bat, so I'll take the length.

Regarding your point on FT vs APS-C, I beg to differ. When I had a fling with an Olympus, I could never adapt to this more boxy picture ratio. And since I don't know how to "lengthen the long dimension" of the sensor in-camera, I could only crop the images to 3:2 ratio. Which actually increases the gap between the two formats. 24MP as been quite the standard on APS-C sensors for some time now, while FT sensors settled on 20MP. If you crop the latter to 3:2 ratio, you end up with about 18 MP, which does not sound all that different from the 16MP APS-C sensors of many eons ago.

Might as well add "Super 35" and "cinema full frame" as other terms to know for "half frame" and "APS-C". It's become a popular sensor size in digital cinema cameras, and with camera makers increasingly catering to video and cinema shooters, you may see the terms more often.

It's the original full 35mm gate size from silent movies, before sound took over some of the film area. Originally around 24mm x 18mm (1.33 aspect ratio), it usually comes shorter these days.

Here's a clear, handy, though cinema-centric visual guide to digital sensors side-by-side (and below that a nice illustrated guide to "crop factor" vs DOF vs sensor size).


At this point, we may as well express everything as a ratio to "full frame." Even if "full frame" is a misnomer, as you say. Full frame won, also as you say. That means 4/3 should be expressed as 1/2, 1" as 1/2.7, and so on. That way, you also have the conversion ratio for lens focal lengths in the name.

How about measuring the diagonal of the sensor area? If it's good enough for describing the size of a TV set, then it should be good enough for sensors!
Although it would have to be in millimetres rather than inches.

I agree wholeheartedly that digital sensor size nomenclature could do with being simplified.

Firstly, drop the confusing or ill-defined terms Micro-Four-Thirds, APS-C, Full Frame, Medium Format and Large Format.

Next, you need to know the actual side dimensions to work out the diagonal (for calculating conversions between the formats). But make the numbers easy to remember by rounding them to the nearest whole millimetre.

The important digital formats become:

17x13mm, diagonal 22mm
24x16mm, diagonal 28mm
36x24mm, diagonal 43mm
44x33mm, diagonal 55mm
54x40mm, diagonal 67mm

And anyway, most photographers live in just one or two formats.

Re: Alan’s comment on APS-H being only in Canon, the Leica M8 and M8.2 (my first digital camera) were APS-H. It also had the advantage, or disadvantage, depending on one’s opinion, of using only the center “sweet-spot” of Leica M lenses, eliminating any poor edge effects.

Mike, the Leica M8/M8.2 APS-H sensors were 3:2 aspect ratio, same as their subsequent “full frame” M digital iterations.

I said it once on this blog and I'll say it again. APS-C is the 35mm of the digital age.

Also 35mm, Tri-X, and cheap Nikon lenses where good enough in Vietnam (My choice) then APS-C should be good enough period.

Mike, your featured reply to Alan is incorrect. APS-H aspect ratio is 2:3, not 3:4.

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