Sensor size questions APS C vs 4 thirds

Discussion in 'Mirrorless Digital Cameras' started by ken_jeanette, Feb 18, 2005.

  1. I read the article here by Bob Atkins concerning APS-C vs full frame, and I became curious. I went into a couple of sites specifically dedicated to the 4 thirds, and they make it seem like that is the largest sensor, although they don't actually say its size "The Four Thirds type sensor is twice the size of the two thirds type sensor, which is commonly used in many digital cameras" According to the Atkins article, APS-C is 22x15mm (and I think this is a "two thirds" aspect ratio. He also states that the 4 thirds sensor is 18x13.5mm, clearly smaller than APS-C. What am I missing in translation between the article and the website. Because of their vagueness, and never having mentioned the size of the sensor, I tend to distrust the 4 thirds website. It seemed to me to be a lot of hype, with very little factual information. So, here I am, at the only place I know I will get the real information. Thank you in advance for any input you may have.
     
  2. Ken,
    You're confusing aspect ratios, such as the 3:2 of 35mm film and APS-C sensors, or the 4:3 of compact digicams, with the archaic naming convention for sensor sizes. You're not alone in this. See dpreview's explanation of sensor sizes.
    The name of the "Four Thirds" system is a reference to size, not aspect ratio.
    --Bill
     
  3. The thing I am troubled by is the way DPReview refers to the new Olympus lenses in the news section. The mention a 180-500 F2.8 lens. When you click on the link you find the lens is a 90-250 F2.8. I guess since the Four Thirds lenses can not be used on a full frame camera this is bound to happen. The issue I have is a new user might say: "Wow Olmpus gives me a 180-500 lens. Canon and Nikon don't have a lens that long." Their marketing doesn't talk about crop factor because it's both an advantage and disadvantage.
     
  4. As Bill said, FourThirds is the name of the Kodak/Panasonic/Olympus/etc sensor initiative. It was perhaps derived from the 3:4 format proportion.

    For reference, the formats are...

    sensor: format - hxw in mm - diagonal in mm
    2/3 sensor: 3:4 - 6.6x8.8mm - 11mm
    FourThirds: 3:4 - 13.5x18mm - 22.5mm
    Canon "APS-C": 2:3 - 15x22.5mm - 27.04mm
    Nikon/Pentax/Minolta "APS-C": 2:3 - 15.7x23.5mm - 28.3mm

    If you compare a 6Mpixel Canon APS-C sensor with a FourThirds 5Mpixel sensor, and consider cropping to an 8.5x11 paper format print with either, you'll see that the difference in size is in reality very small. FourThirds is smaller but not by a very large percentage.

    Godfrey
     
  5. Godfrey, The sensors used in the Four Thirds systems do have a 4:3 aspect ratio, but they are named for their 4/3-inch size, not their aspect ratio. Visit the link I posted above to see an explanation of what 4/3-inch, 2/3-inch, 1/1.8-inch, etc. mean. --Bill
     
  6. Thanks, Bill. I have been to that page many times, it is in my bookmarks for reference. :) What I was suggesting was that perhaps the 4/3" size designation was a part of the reason to name the format initiative FourThirds, and that the sensor proportions are also 4:3 (or 3:4) so they were trying to make it all related. FWIW: The sensor size designations like "2/3" and "4/3" are to my mind a very odd archaism to keep around. I prefer referring to the size of the format for a digital camera as it helps me understand the relationship between optical focal lengths and field of view better ... Much easier to see 6.6x8.8 vs 24x36, for instance, than '2/3"' vs "full frame". Even "APS-C" is a silly way to describe a sensor size as APS film formats are not the same..."16x24mm" vs "24x36mm" is much more understandable. 14x18 vs 16x24 approximations makes the actual size difference between FourThirds and APS-C a lot more understandable as well. Godfrey
     
  7. Godfrey wrote: '"16x24mm" vs "24x36mm" is much more understandable' That's for sure the way I think of them! --Bill
     
  8. "The issue I have is a new user might say: "Wow Olmpus gives me a 180-500 lens. Canon and Nikon don't have a lens that long." Their marketing doesn't talk about crop factor because it's both an advantage and disadvantage." It would be nice if everyone spoke in terms of angle of view rather than focal length.
     
  9. You can't fight city hall. The manufacturers use the terms "APS-C" and "4/3", so that's what you're stuck with. Olympus are quite clearly and obviously making their smaller format size into a "feature", and are thus not-too-subtly marketing their lenses such in a way that emphasizes double their actual focal length and downplays their smaller format size. If I were in their advertising department, that's exactly what I'd do. They don't mention the fact that smaller formats give greater DOF, so you need faster lenses to blur backgrounds, but I wouldn't either. The Olympus system is interesting and technically quite nice. I doubt it will get far, but it will develop a niche for itself with a band of loyal users who will get great results from it. There's no doubt that the equipment itself is well designed and well built, but given that there's no price advantage despite the smaller format and lenses, they're fighting an uphill battle against 35mm and APS-C.
     
  10. However, what some people are going to be jealous of are these two new lenses, the 14-35mm f/2 (equivalent to 28-70mm f/2) and the 35-100mm f/2 (equivalent to 70-200mm f/2) which does not exist with any of the current systems. In fact, I haven't heard of a single zoom lens with an f/2 aperture....
     
  11. Let's wait for prices to be announced before getting jealous. My P&S digicam has an f2 zoom. If you make the sensor small enough you can make really fast zooms. I think the 18x zoom lens on my camcorder is even faster.
     
  12. David Bedell:
    .."It would be nice if everyone spoke in terms of angle of view rather than focal length."..


    But which angle of view... H, V, D? and which format proportion? The problem is multivariant. I find I no longer think in 35mm terms at all. I think in terms of the 16x24mm format: a 16mm lens is an ultrawide, a 24mm is a wide, a 35 is normal, a 50 is a portrait tele, an 85 is tele, and a 135 is a long tele. Once you become familiar with the characteristics of your DSLR's format, it simplifies things a lot to think in terms relative to ultrawide to long tele rather than film camera focal length equivalents.

    Bob Atkins:
    .."You can't fight city hall. The manufacturers use the terms "APS-C" and "4/3", so that's what you're stuck with."..


    With a defeatist attitude like that, you'll be stuck with whatever those who feel they can get away with things want. ;-)

    Panasonic's recent statements regarding FourThirds and collaboration with both Olympus and Leica could heat up the FourThirds technology quite a bit. More DoF is not necessarily a bad thing when it comes to tele lenses either ... Why is everyone so concerned with blurring backgrounds? It's just one visual convention for subject separation ... is it the *only* one of any merit? The great DoF (and speed!) of 35mm film over 4x5in and medium formats was considered a major plus.

    Daniel Powis:
    .."some people are going to be jealous of are these two new lenses, the 14-35mm f/2 ... and the 35-100mm f/2 ... which does not exist with any of the current systems."...


    Speed is nice, but I think both of how expensive these lenses will prove to be as well as how bulky and heavy they might be. The Pentax DA16-45/4 is already about as bulky as I would like to carry, and it's not particularly heavy ... going to an f/2 would push it way over the bulk/weight threshold for me and I suspect it would cost far more than its current $430.

    As always, there are a lot of tradeoffs and compromises to ponder.

    Godfrey
     
  13. The only other problem with the f2 zooms is the availability, scheduled for "4th quarter 2005". These days it seems to be increasingly popular to announce products up to a year ahead of when they actually become available. Both Tokina and Tamron have been talking about their new wideangle zooms since last summer and they still haven't been seen on the street.
     
  14. I know what APS is, but is APS-C? That is, what does the "C" mean?
     
  15. ShunCheung

    ShunCheung Moderator

    On paper, those fast f2 zooms for the Olympus 4/3 system sound great. I too am a bit skeptical about the late 2005 delivery date. Moreover, I wonder what size and price are going to be like. (Olympus has a 300mm/f2.8 that is sold for $7000 new, about twice as expensive as other 300mm/f2.8's.) I think it is wise to wait until you can actually get them before getting overly excited. If it works out, those zoom can be great for event photography.
     
  16. Mike asked:
    "I know what APS is, but is APS-C? That is, what does the "C" mean?"
    As Godfrey indicated, APS is not just one format, but rather a family of formats. When people say simply "APS" they usually mean "APS-C." See, for example, Answers.com for a brief explanation of the APS formats.
    --Bill
     
  17. Oh, that's right C/H/P. I was thinking it was a new format.
     
  18. I think the "C" stands for "Classic". "H" is for HDTV and "P" is for panorama. They differ both in actual size and aspect ratio. The Canon 15mm x 22mm sensors are close (but not identical) to APC-Classic which is 16.7mm x 25.05. The Nikon sensors are closer at 16mm x 24mm I think
     
  19. Bob Atkins said:
    .."The Canon 15mm x 22mm sensors are close (but not identical) to APC-Classic which is 16.7mm x 25.05. The Nikon sensors are closer at 16mm x 24mm I think"..


    Gathering information from earlier in the thread:

    APS-C: 2:3 - 16.7x25.1mm - 30.12mm
    APS-H: 9:16 - 16.7x30.2mm - 34.5mm
    APS-P: 1:3 - 9.5x30.2mm - 31.65mm
    FourThirds: 3:4 - 13.5x18mm - 22.5mm
    Canon "APS-C": 2:3 - 15x22.5mm - 27.04mm
    Nikon/Pentax/Minolta "APS-C": 2:3 - 15.7x23.5mm - 28.3mm

    Close but not the same. There's almost as much difference between APS-C format and either of the two "APS-C" sensors in use as there is between those sensors and the FourThirds (4/3) sensor, if you take into account the usable area for printing to a standard 8x10 or 11x14 inch print.

    Godfrey
     
  20. I think that physical size of the 4/3 sensor is not important if you compare it to an APS-C Because the 4/3 sensor is FFT (Full frame transfer) where as the APS-C uses a channel on the sensor for data transfer.
     

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