Sensor technology advancements

When digital cameras were developing, in the early 2000s, there was a concern about sensor noise creeping up with the increase of resolution. The logic was simple: the sensor is an x*y array of photo elements. Each has a certain percentage of surface area that’s actually sensitive to light, and that area is at the bottom of the “cup” that is the photo element. Then there are the readout lines that reduce the photosensitive area even further. Each “cup” is basically a capacitor that increases its charge with impact of each photon to the photosensitive material at the bottom. After exposure, the camera reads out the capacitors, converting the level of charge into a digital number; let’s say it’s 8-bit, so there are 0-255 levels of brightness. This data makes up the raw file, which is grayscale. The colour information is created by the demosaicing process, since there is a Bayer matrix of colour filters in front of the sensor, and with some software magic in the raw converter, which consists of demosaicing and applying the gamma curve, you get the kind of a colour image you expect.

This, of course, is super simplified. In reality, not all sensors are of the same type; there are CCD and CMOS sensors, where CCD has a much bigger photosensitive area, and the CMOS sensor has theoretically all the disadvantages you can think of; much smaller photosensitive surface, and of lower photoelectric quality, and so on. The advantages are that CMOS has transistors for signal amplification for each pixel, at the very source of the signal, before reading it out. This, combined with the fact that CMOS technology is standard semiconductor tech that’s cheaper to make, eventually not only made up for all the drawbacks, but in fact created sensors that have much better behaviour at high gain settings, also known as high ISO. So, how does that work, exactly?

Well, we need to understand the origins of sensor noise, and there are many. Heat is one. Electromagnetic induction is another. Then there is the readout noise, where reading out each line passes electricity through it, and basically creates inductive noise in the adjacent lines. Then there’s the electromagnetic noise created by the computer in the camera (yes, a digital camera is essentially a computer very much like your smartphone) which needs to be shielded, and that’s kind of hard to do if you want to reduce weight as much as possible. Also, the computer generates heat, which eventually finds its way to the sensor, and then you realise why astronomers cool their camera sensors with liquid nitrogen. As it turned out, most of those problems were solved admirably in the early years of digital camera evolution, but some, like the demand for more photosensitive area, are a matter of physics and nothing can be done about them. Well, it turned out that people who made very small sensors for smartphones got very creative in getting around those issues since the financial incentives were huge, and people bought phones primarily based on how good the camera was. One of the major inventions was the backside illuminated sensor, which means that it’s no longer designed as a cup with photosensitive material at the bottom; basically, they turned the cup around so the photosensitive material is on top, and the amplifiers and readout lines are on the bottom. This increased the photosensitive area on the CMOS sensors by an order of magnitude, and probably allowed for putting more electronics per pixel, giving the designers room for more sophisticated signal processing on the source.

So, the expectation somewhere in 2004 was that you can put 11 megapixels of resolution on the 35mm full frame sensor, but you’ll get high noise at ISO 1250 already, and chromatic aberrations and vignetting are going to be nasty since the photons are hitting the “cups” in the corners at high angles of incidence, which means that most photons end up in the “walls” and not the sensitive area at the bottom, and also various wavelengths hit the sensitive area at different angles. It seemed that the increase in resolution is not going to be steep, and that, maybe, lenses have to be designed with that in mind; also, big sensors increasingly looked like a bad idea in the digital age, being expensive and creating huge vignetting and chromatic aberration issues.

However, Sony made a technological breakthrough making sensors for iPhones and other smartphone cameras, and when they moved that same technology to 35mm sensor size, it turned out they can make a 42 MP sensor with no vignetting and CA issues, and with less noise at ISO 6400 than the older 11 MP sensors had on ISO 1250. As it turns out, most of the old problems with pixel size, readout noise and cup-shaped pixels had limitations that stemmed from uninventive electronics design, rather than the limitations of quantum physics, and selling billions of phones tends to motivate technological development much better than selling millions of cameras.

So, what’s the current state of sensor technology, from the position of a photographer?

I look at the image quality from the position of what the colours look like, how much noise there is at low and high ISO, how well the noise cleans up in processing, and if there are other image defects such as banding, vignetting, CA and so on.

My initial impression is that the modern sensors have somewhat higher noise at low ISO compared to the older cameras, but in absolute terms this is a mild texture comparable to film grain and it doesn’t reduce image quality. However, when we take the resolution into the equation, and if we downsample a 61MP image to 6-8MP typical for those older cameras, we’ll get a much cleaner image, so there’s that. Basically, the low ISO noise is greater but it doesn’t matter. High ISO noise is improved to the point where I now consider ISO 12800 useable, when earlier ISO 3200 meant I was really pushing it. This means I now have two stops greater high ISO, and with better results.

As for the colours, they were excellent before and they are excellent now. If anything, I now have high-ISO colours that are comparable to low-ISO colours before.

As for the dynamic range, this improved significantly from the earlier years, and that’s the most surprising part, because the expectation was that the dynamic range will go down as you put more pixels on the same surface of silicon. I think we gained about two stops of useable dynamic range.

To summarise, the 35mm sensor resolution between Canon 1Ds and Sony A7RV increased from 11 MP to 61MP, high ISO increased from ISO 1250 (which looked less than great) to ISO 12800 (my personal limit for still retaining excellent image quality), and the dynamic range of the image is at least two stops better. Also, the vignetting and CA issues were solved, and the colour quality either remained the same or was improved.

So, the expected image degradation after increasing resolution by a factor of almost 6 did not happen, and instead we have the increase of image quality across multiple dimensions simultaneously. Also, since most photographers don’t actually need more than 24MP of resolution, the megapixel race seems to have peaked out, giving us 35mm cameras with sensor resolutions that strain all but the most perfect of lenses, incredible colour depth, incredible dynamic range and excellent behaviour on high ISO values.

As for the smaller sensor sizes, the APS-C and four thirds, they seem to have peaked out at 24-26MP resolutions, which is excellent and perfectly useable for most professional and amateur intents and purposes. A further increase in resolution would hit hard into the diffraction limits of their respective formats, which means the absolute size of the aperture would interfere with light and soften the image, and since this is an actual physical thing, it can’t be helped in any way other than increasing the format. However, by avoiding diffraction limits in this manner, you encounter shallow depth of field issues on larger formats, and this is not necessarily an upgrade.

Image quality from a 2003 camera, 5MP.

Image quality from a 2014 camera, 24MP.

Image quality from a 2022 camera, 61MP.

A corollary of this is that if you are interested only in low-ISO image quality, you don’t need to print big and you want excellent colours and normal dynamic range, not only will a 10 year old used digital camera be perfectly fine; some of the 20 year old models will be fine as well. This means that an amateur photographer can get into photography at a very high level of image quality with very cheap used gear, unlike the early days of digital photography where even the new stuff was still unsatisfactory, the used stuff was terrible, and the prices of the new, state of the art gear were astronomical. The prices of used digital gear of high quality are comparable to what the prices of good used film gear were in the golden era of film, when one could get into photography cheaply, and still expect to be able to produce great looking images. For all intents and purposes, this is ideal.

Utrawide, but not ultraweird

I have the first batch of pictures made with the FE 14mm f/1.8 GM (and Biljana has a series with the RF 16mm f/2.8).

14mm G master is wider than the more conventional 16mm, but not so much that the lens would require adaptations to the shooting style; basically, it’s an ultrawide, and you use it as such. Biljana’s 16mm Canon focuses closer, which is very useful for certain kinds of near/far compositions, but the actually important difference is the aperture. f/1.8 really allows you to “see in the dark”, and especially combined with the sensor stabilisation in the A7RV it allows you to get sharp pictures of stars at 1/3s hand-held. Biljana doesn’t have sensor stabilisation in the Canon RP body and the RF 16mm f/2.8 doesn’t have optical stabilisation, which forced her to try insane things like 1s exposures hand-held, which of course can’t be done. However, while there was still a reasonable amount of light available, it all worked fine, and well into the deep blue hour, but not past the point where we could no longer see where we were going without a flashlight. All in all, the 16mm is a very practical lens that allows you to get f/2.8 without paying through the nose for a 16-35mm f/2.8 zoom, or having to carry it uphill for hours. I couldn’t actually evaluate sharpness of either lens because we used them for real life photography as this type of lens is supposed to be used, not taking pictures of a flat surface and then pixel-peeping the edges. The truth is, if you’re using a wide angle properly, you are perceiving flare, sun stars, contrast, colours and sharpness around the point of focus much more than anything else, and when I look at the actual pictures, both lenses did a nice job. The 14mm f/1.8 just has 1.3 stops of light advantage in the dark, which actually matters a lot if you want to hand-hold shots with stars visible in the night sky. Both lenses are very resistant to flare with sun in the frame, the contrast and colours are excellent, and the files would print big. You do, however, get what you pay for with the G master lens, which is optically better than any ultrawide has a right to be, and that’s wide open at f/1.8. Considering how shitty 50mm f/1.8 double Gauss designs are wide open, that’s actually mind-bogglingly insane, considering how hard it is to design a decent ultrawide lens. This one is not decent; it’s basically a perfect lens, to the point where I just use it as I would any other fast prime, without thinking that this shit should be impossible for an ultrawide, and in fact was ten years ago. The Zuiko Digital 7-14mm f/4, for instance, had severe flare with sun in the frame, and the total absence thereof on the G master is the most shocking aspect of its design that I noticed. If I’m trying to look for things that could be improved… there’s basically nothing. It’s reasonably small and light for what it is (the Zuiko 7-14mm f/4 zoom is much bigger and heavier, and that’s for 4/3, not 35mm), it’s reasonably priced for a top-tier lens, it’s built well and it’s optically so good it feels surreal, but in a good way, because it just works and doesn’t let you know there’s anything weird about that.

The 16mm f/2.8 Canon is impressive in its own way. It’s so small it almost falls into the category of pancake lenses; definitely pocketable, and on a general image quality scale (what you see looking at the picture as a whole, rather than magnified details) it’s excellent. The most important aspect of this is resistance to flare with sun in the frame, contrast and colours, which are all excellent. If the G master shocks you with its optical performance, this one shocks you with the fact that something this small, light and inexpensive works this well at all, in lighting conditions that are not completely unreasonable. Basically, while Biljana still had enough light to work with, she was producing pictures that are a very close match to mine, but when she ran out of light and tried to hand-hold 1/3s shots, there was a sudden drop where the shots were no longer usable due to motion blur, while I kept cranking out completely unreasonable stuff.

When I would have to hand out recommendations, I’d say both lenses are excellent for what they are, and in both cases you get good value for the money. The Canon RF is small, light, cheap and capable of cranking out great images. The G master is absolute insanity, a 14mm lens that makes a typical 50mm f/1.8 look like a piece of crap optically, is as sharp as a macro lens, produces no flare or contrast reduction with sun in the frame and lets you take pictures of constellations handheld.

Ursa Maior supra crucem

But I would say that the Canon RF works better in daylight or at least reasonable amounts of light, for anything from interiors, urban photography to landscapes, and the G master is an optically ideal lens without any real limitations, unless you want to use filters, which can’t be done due to a bulbous front element. The actual question is whether you want to take pictures that really take advantage of such a lens, and for most people the answer will probably be “no”, and I would recommend something like a 16-35mm f/4 zoom, which can give you the ultrawide angle but with the flexibility to use something more reasonable for most shots. There’s also a skill issue with the ultrawides; you really need to know how to work such a lens and compose things in ways that will take advantage of it, instead of getting empty compositions that look like shit. So, I would definitely recommend your first ultrawide to be a 16-35mm f/4 zoom, because those are cheap, practical and reasonably light, giving you the option but without forcing it upon you immediately. However, if you find out that such an ultrawide zoom is what you use most of the time, and mostly at the wider end, then an ultrawide prime might be a thing for you. Both Biljana and I actually prefer 35mm fast primes for most things, and we find their perspective more natural, so ultrawides won’t be the first tool we reach for, but they are very nice to have when we need them.

Zombie apocalypse

August on Hvar, a notable tourist location. You can imagine. Biljana and I went to the store to get fish for lunch, that ended up with her going to the store and me driving in circles on the parking lot, waiting not for a free spot, because that’s not happening, but for her to come back so we can get the fuck out.

On the good note, the FE 14mm f/1.8 GM arrived:

That’s the first time I have a combination of ultrawide angle and wide aperture. Usually, I’ve been using wide lenses stopped down, so this is a new thing for me. There’s a lot of haze in the air so I’m not sure about photographic opportunity, but haze can create very nice orange and purple hues in the sunset, so let’s see.

Pagrus pagrus; A7RV, 14mm f/1.8

Blue hour in the hills

I had a pretty long pause with photography, since I was in a heat wave that doesn’t really encourage going out with a camera unless you really want to have a heat stroke, and it’s also a tourist season where everything’s crowded and I hate that.

Also, spending karma in industrial quantities is about as much fun as it sounds, so I wasn’t in a mood for anything really. I was processing that shit, trying not to go crazy too much, and eating too much food because I was at home and stressed out.

Recently, I figured out that if I climb the local hill, which is basically the top of the island, the temperatures are manageable even during the summer if I start late enough, and return in the deep dark of the night. Of course, once we get high enough to get out of the heat and the crowd, photographic opportunities start making themselves apparent, and then of course I see that I only have my phone with me, because climbing in hot weather is hard enough carrying my own excess weight, let alone camera gear. 🙂 After several frustrating experiences with iPhone raw files taken during the blue hour, I actually took the Sony A7RV and the FE 35mm f/1.4 GM with me yesterday, and we also stayed out longer than usual which means that the sun set while we were on the top, and we were descending through the blue hour and into complete darkness. So, here’s the album and some individual shots. This is Biljana’s album.

I still can’t believe I got completely sharp 61MP hand-held shots in deep blue hour with stars clearly visible in the shot, and the only thing I felt I was missing was the ability to get ultra wide angle of the Zeiss 16-35mm f/4, but of course the Zeiss at f/4 would run out of light far, far before I took some of the best shots, so I would have to carry the tripod with me as well, and even if I could convince myself that it’s a good idea, fiddling with a tripod in those conditions is really impractical and possibly even dangerous, because you can barely see anything in the conditions where that camera manages to get all those colours. So, I’m considering FE 14mm f/1.8 GM, which I didn’t buy because I thought it overlaps with the Zeiss so much that one would never be used, and its strongest point is astrophotography in the mountains. Well, now that looks like more than just a fringe use case.