Sensors

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This topic contains 13 replies, has 4 voices, and was last updated by  Nathanael & Samantha Frazer 4 years, 1 month ago.

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  • #9749

    James Staddon
    Keymaster

    I’ve been doing research on camera sensors recently and had some questions for folks more mechanically inclined than I for the community.

    Here are the facts: The size of a full frame sensor is about as big as “affordable” sensors can get. A full frame sensor measures 36 x 24mm. The sensor is cram full of pixels, measured in megapixels. All things equal, a larger pixel will result in a higher quality image. You can only fit so many “larger” pixels on a constant-size sensor.

    Here is the question: Why then are camera manufactures trying to cram more pixels onto the sensor by increasing the megapixels? (Canon’s latest camera launch boasts of a 50.2MP sensor!)

    Here is a followup question: Obviously, 50MP is overkill. So what is the megapixel threshold at which the pixel size renders the highest image quality while still providing a comfortable pixel count for large, high quality printing?

    • This topic was modified 4 years, 8 months ago by  James Staddon.
    #9751

    Ezra Morley
    Moderator

    Wow James! That’s quite the question, I’m afraid no one here is qualified to answer it properly! You’d need to talk to someone who works in camera design and engineering.

    I do have a few thoughts on the matter though… 🙂

    First, I was rather surprised that the maximum ISO limit was only ISO 6400! (Expandable to 12,800) Canon’s new camera the 7D MK II goes all the way up to ISO 51,200, and it’s a crop sensor camera! (Check out the link, near the bottom of the page for the ISO comparison.) That seems to indicate that noise levels any higher than that would more than likely be unacceptable. But then again, the camera is aimed toward “those shooting landscape and architectural photography, as well as those shooting commercial or high-end editorial work in the studio” Used in those situations, you would have no need for high ISO levels.

    Here’s a shot taken at ISO 800, you can see for yourself that the amount of detail is impressive!

    If you’d like to see for yourself what kind of detail you can get from the 5DS and 5DSR, then take a look for yourself! The detail is simply astounding! I cannot imagine the workflow though, imagine 100s of RAW images that are 60-100 MB each!

    Speaking of print sizes, with 50 MP (at 300 DPI), you can get approximately a 29″x19″ print.

    #9753

    James Staddon
    Keymaster

    That is very interesting, @buddingphotographer. Something I hadn’t thought of.

    I guess each camera manufacturer will never make “the perfect camera”; otherwise they wouldn’t make any money with the next camera release! 🙂

    #9948

    timtam
    Participant

    I think what is happening is that Canon is going after the high-end segment of the commercial medium format camera market.

    They are trying to compete with the medium format professional cameras such as those from Hasselblad. Those are $45,000 cameras with sensor sizes of 32.9 x 43.8mm that capture just incredible detail and produce 65 MB files per image. Hasselblads are used for high end fashion and commercial product and advertising photography where the images are blown up to poster or bill-board size.

    #9949

    I’m certainly not qualified to answer that question, but I’ll give it a jab.
    **Caveat- I have ad-blocker on chrome, so I am unaware if there is inappropriate content on some of the links I have here, but I believe these sites to be safe.
    Camera makers are increasing megapixelage (if that’s a word) due to market pressure, and people’s real needs to print the size of a wall. As to market pressure, “this one goes to 11” is a perfect example of what marketing is. For professional event photographers, in a world where everyone thinks themselves to be a photographer, it could be helpful to have a camera that appears better than your client’s just to make the sale. As to real need, there are those who are paying 1000$ for multi-row panorama heads (http://www.reallyrightstuff.com/Shop/Panorama-Packages-for-Single-Multi-Row/Multi-Row-Pano-Elements-Package.html) just to get more detail in there shots. It would be cool for those people to just put an 11-24 (http://www.the-digital-picture.com/Reviews/Canon-EF-11-24mm-f-4L-USM-Lens.aspx) on a 5ds-r and get the whole thing in one snap. With a sharp lens, 50 mp full-frame allows cropping say, a full-body shot to a head shot. So that’s attractive to event photographers, and wildlife photographers. For wildlife photographers, the 5ds-r has a built-in crop mode, which should help the buffer. I don’t think that 50mp is overkill, frankly. In a few years we’ll be viewing our photos on 8K displays, which represents roughly 40 megapixels, so we’ll be grateful then that someone was shooting on a 5ds or a d810 back in 2015! 😉 Lastly, picture that is down-res’ed in PP to say 20 mp will appear sharper than a picture taken at 20 mp due to bayering.
    As to too many pixels spoiling the image quality, The only thing we loose with more pixels is a per-pixel snr. Dynamic range and colour sensitivity are actually theoretically improved by having more pixels (by de-res’ing) Noise levels *per pixel* will be higher, yes, but by binning pixels, on-chip, or in PP, noise levels will be effectively reduced to levels on a similar-sized sensor with less pixels. 2 photosites receive as much light as 1 photosite that is twice the size. By having more pixels, there is less pixel area due to the circuitry (disregarding a bicmos sensor) but the micro-lenses make up for that, at least in theory. So basically if there’s enough photons to go around with all those pixels, a 50mp sensor will bring a phenomenal amount of detail to the table. If there’s not enough light, then we have to start reducing the size of the image – which will give it similar low-light results to a camera that started off with less (and larger) pixels in the first place.
    A real world example: the 7d mark ii actually has a 40 megapixel aps-c sized sensor, with photosites binned together in pairs to create on-sensor phase detection autofocus. (dpaf) That means the pixels are twice as small as a similar 20mp crop camera, but the 7dii has a very similar final snr to any of its’ contemporaries – because the smaller pixels are combined to mitigate noise. The 7d mark ii also made a large step forward in terms of dark current and thermal noise, as well as the downstream electronics, so I would assume that such would help the smaller pixels survive until they’re binned. http://www.clarkvision.com/reviews/evaluation-canon-7dii/
    As to iso levels, canon has claimed two things: firstly that they established the maximum iso based on what the professionals they interviewed needed. (that’s on a interview dpreview did with them lately http://www.dpreview.com/articles/5301008561/cp-2015-canon-interview-every-day-im-saying-speed-up) secondly canon claims to have increased the density of the cfa. (colour filter array, and sorry, can’t find a reference for that one, just know I read that a while back) That would give the sensor much greater colour accuracy, at the expense of a loss of light, which would result in lower snr. (signal-noise ratio) That would be a similar situation to the 5dii and the 1dsiii which have identical sensors. The 5dii is optimized for low-light (less dense cfa) and the 1ds is optimized for colour accuracy. http://www.dxomark.com/Cameras/Compare/Side-by-side/Canon-EOS-5D-Mark-II-versus-Canon-EOS-1Ds-Mark-III___483_436 Incidentally I find the 5ds is NOT the successor for the 5dIII (wait for the 5div) but is more a natural descendant of the 1ds series bodies which have always been about high megapixels (12 megapixels in 2002!) and controlled environments. The 5ds is aimed mainly at landscape and studio photographers who shoot almost exclusively at iso 100, and can control their own light.

    I think Timtam has it: Canon has definitely set themselves up to make a jab at the medium-format world, with their lens releases in the last few years, and the 5ds-r, I think they have a good chance at it.

    No, I don’t think we’ll ever have a “perfect” camera, because people’s needs vary too much – just look at the 1dx at 18 mp. Photojournalists want speed, and a 50 mp camera (roughly 60mb) at 14 fps would require 840mb/s write… While that will be possible in the future, energy and thermal restraints can’t allow that much power into a small camera body yet, let alone the cost of implementing such a technology. For now, canon for one has been increasingly segmenting their product lines for such reasons (think 7dii vs 6d)

    I hope this is at least a bit coherent

    #9962

    Ezra Morley
    Moderator

    I agree that 50 MP isn’t necessarily too much, it depends entirely on the user. Probably at least 90% of photographers don’t need 50 MP though. Like @timtam said, the 5DS is probably aimed to lure people away from the medium format market. Although, if you really want a high end 50MP sensor, for only $8,496.95 you can get the Pentax 645Z, a modern CMOS medium format camera that is actually cheap, if you compare it to other medium format cameras, like Hasselblad’s H5D-50c which is also relatively new, with a 50MP CMOS sensor, only $27,500.00! And even as cheap as the Pentax is, it’s got better specs in most regards than the $30,000 one! The Pentax has a full-featured advanced auto focus system, the same one as it’s high end DSLR’s. Not to mention, it’s probably the only medium format camera in the world that has a tilting LCD screen.

    So, @jamesstaddon, forget about upgrading to the 1D-X, just wait a few years till the Pentax 645Z is down to about $6,000… 🙂

    #10062

    James Staddon
    Keymaster

    Interesting insight, @timtam. Makes sense.

    Most enlightening, @nasa. There are certainly a lot of factors to consider I was not aware of. Thank you so much for the comprehensible explanations.

    It really does has everything to do with perspective. Working mostly with beginner photographers, I tend to forget about all these details.

    Another thing I’ve been wondering about is which is better, CCD and CMOS, if anyone cares to reply. Is it true that CMOS is most common today in “affordable” cameras for the simple fact that it’s cheaper to produce? I was always under the impression that CMOS was “better” technology. But the comment thread on http://snapsort.com/learn/sensor/type got me thinking that this may just be a preconceived perception due to the fact that CMOS is “newer”.

    #10065

    The only thing that comes immediately to my mind is how many video cameras still use ccd instead of cmos because, until the last year or so, global shutter only worked for ccd, due to cmos electronics not offloading fast enough. I could be wrong. (Global shutter prevents ‘wobbly’ footage, skewing during a pan, etc. Theoretically with a global shutter, a camera could have a flash sync as fast as you want)
    The technologies are actually about the same age, but CMOS was far too expensive to produce in the 60’s and 70’s to be viable (due to technological constraints) So CCD dominated the market until the early 00’s

    Now, after a little research, because CCD signal (because it is offloaded by line in analogue fashion, before being digitized) a whole row of pixels can get saturated as the oversaturated pixel carries it’s signal over to the next one. (imagine your blown out highlights making rows of blown out pixels all the way across the image) This is called smear, and CCD’s are immune to this as each pixel is digitized by it’s own individual transistor, thus every pixel being treated independently.
    CMOS sensors are made on standard silicon wafers and are thus dramatically less expensive to produce. (now) CCD’s are more sensitive and less noisy.
    That’s all for now. It sounds like interesting reading topic. I’ll let you know if I learn anything else

    #10100

    Ezra Morley
    Moderator

    If you’re interested in the technical details, here’s a detailed report on the differences and advantages/disadvantages.

    http://www.teledynedalsa.com/imaging/knowledge-center/appnotes/ccd-vs-cmos/

    Here’s an article from the B&H website which tells some details about rolling shutter vs. global shutter, and the smearing which can happen with CCDs.

    http://www.bhphotovideo.com/c/find/newsLetter/Comparing-Image-Sensors.jsp

    #10128

    James Staddon
    Keymaster

    Thanks guys! Yes, please do let me know the gist of what you learn as you have opportunity @nasa.

    #13460

    Aaaannd, if 50 megapixels isn’t enough, canon is working on something, – though this has yet to translate into a real product we can purchase- a 120 megapixel camera 😀 http://www.canon.com/news/2015/sep08e2.html This is an official press release from Canon, and indicates a very real product in the making and not just some fly-by-night rumour. However, these things are years in the making and I wouldn’t expect to see a real product announcement before 2017.

    I saw that and immediately thought of our discussion here.

    I’m thinking about 160 mb raw files…

    #13471

    James Staddon
    Keymaster

    That’s seriously hilarious. 🙂

    #13495

    Ezra Morley
    Moderator

    Wow, that’s interesting! I actually just saw this article just the other day, also from Canon…

    http://www.the-digital-picture.com/News/News-Post.aspx?News=15732

    Attachments:
    #13524

    Yes! I thought that was interesting also. Canon has been experimenting with aps-h size high megapixel sensors for some time now, and announced a 110 mp sensor.. over 5 years ago? something like that. It’s interesting from an R&D perspective but unlikely to ever make its way into a product.

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