The Digital Sensor: A Guide to Understanding Digital Cameras
by Wesley Fink on April 21, 2008 1:00 AM EST- Posted in
- Digital Camera
Sensor Size and Multipliers
Canon had become a dominant player in the SLR market after their successful launch of the EOS all-electronic mount for AF. Canon was also large enough with enough resources to develop and manufacture their own sensors. Canon launched a professional standard APS-H camera, with a 1.3X lens multiplier that used existing Canon 35mm lenses. Later, when Canon was ready to create a consumer digital SLR market they used a smaller 22.2x14.8mm sensor with an area of 328mm² and a lens multiplier of 1.6X. This is 38% the area of a full-frame sensor.
More recently, Canon has championed the full-frame sensor in their pro cameras and in their pro/amateur 5D model. Larger sensor manufacturing cost has dropped as digital sensors have evolved and it now appears likely the APS-H (1.3X lens multiplier) will eventually drop form the Canon line. Since no lenses depend on that image circle all current Canon full-frame lenses, such as those used with the APS-H cameras, will remain usable on the full-frame sensor pro models that will replace them.
Nikon, Pentax, and Minolta all had significant success in the 35mm film market, so all three had a vested interest in preserving their 35mm lens mount and keeping their current 35mm system users happy. However, none of these three had the resources to develop and manufacture their own sensors, so they partnered with sensor manufacturers to produce digital SLR cameras. In recent years that partner has been Sony, so all three manufacturers have basically adopted a larger 23.6x15.7mm sensor with a 1.5X lens multiplier.
Sony purchased the Photo Imaging division of Konica Minolta in 2006 and carried on the Minolta lens mount under the Sony brand. Today Sony both manufactures their own Sony brand cameras with Sony sensors and they continue to sell sensors to Nikon, Pentax, and Samsung.
Olympus was a huge player in the digital compact market as the market began its slow move to the digital SLR. While Olympus had been a very successful player in the film SLR market, they lost market in the SLR Auto-Focus wars kicked off by the success of the Minolta 7000. Olympus AF cameras remained a fringe product and Olympus eventually exited the market to concentrate on their compact digital offerings.
Olympus had a stake in the compact market remaining dominant and they had little legacy 35mm business to protect. Both developments made them late to the digital SLR market, but they made the best of it with a different approach than the other DSLR players. Olympus developed a new all-electronic DSLR lens mount and camera system based around a Kodak sensor with a 4:3 ratio instead of the 3:2 common in 35mm. With no legacy lenses to protect, the concept of lens multiplier is basically meaningless when talking about the Olympus DSLR system, but the diagonal is 1/2 the 35mm full-frame so lenses are equivalent to a 35mm lens at twice the focal length.
Olympus and its partners also made the 4/3 standard open - that is, it's available to any manufacturer. Currently Olympus, Panasonic, and Leica are producing 4/3 cameras and lenses but other manufacturers may join them in the future. Olympus is also now using sensors manufactured by Panasonic, a development partner, in their 4/3 cameras.
Sigma is best known as an independent lens manufacturer, but they have been producing SLR camera bodies for almost 30 years. Sigma introduced their first digital SLR with the SD9 in 2002. Sigma is the only DSLR manufacturer to use the unique Foveon sensor, which captures all three colors in a digital image in three layers - red, blue green - on a sensor. All other current digital sensors are based on Bayer sensors, which capture all three colors in mosaic patterns on a single sensor layer. Colors are then restored by an interpolation process called demosaicing, which theoretically converts the three color mosaics into smooth full-color images.
For this discussion, the current Sigma SD14 should be considered a niche DSLR player with very small market share. The Foveon sensor falls between 4/3 and the Canon 1.6 in size and has a 1.7X lens multiplier. Sigma is the only third party lens maker to produce lenses for all the camera systems discussed here. Some are full-frame designs with digital coatings to mount on full-frame or smaller digital sensor SLRs. Other designs are based on the largest 1.5X APS C image circle and are designed to work with smaller DSLR sensors ranging from 1.5X to 2X lens multiplier.
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Johnmcl7 - Monday, April 21, 2008 - link
I do agree with you there that it is desirable to have deeper depth of field (particularly on macro) but I think the difference is that on an SLR you have the choice - you can shoot wide open and have shallow depth of field or you can stop down (and normally have to use up the ISO advantage) to get depth of field. On a camera with a small sensor you are generally stuck with the deep depth of field whether you want it or not.John
finbarqs - Monday, April 21, 2008 - link
I hope nobody is using F/1.2 when shooting a portrait. Unless you want only a nose to be in focus. With something THAT shallow, you either have to REALLY step back and use distance to your advantage to get what you want in Focus. Professional Wedding photographers will not TOUCH anything above f/5.6 as you don't want to get ONLY the bride in focus while the groom is OOF.People, remember there are multiple factors that affect DOF. Aperture is definitely one of them, distance, and Focal Length.
Obviously you want something very shallow with great bokeh, then you would get close to your subject, open up your aperture, and have a telephoto focal length.
The thing is, on a FF sensor, you "see more" on the same focal length as a cropped sensor. Well put wesley, a 50mm is a 50mm. For those of us with cropped sensors, slap a 50mm on your camera. (or zoom to 50mm). Look at your subject with your naked eye, then look through the view finder. SAME SIZE AND SHAPE! Nothing gets larger! Supposedly a telephoto range (greater than normal) should have some zoom effets shouldn't it? I mean APS-C sensors are either 1.5 or 1.6 smaller than a full frame, that means the normal focal length should be around 27mm? So 50mm should be 75mm for nikons and 80mm for canons! That means you should see some zoom in 50mm! but nope! you don't! in fact, the only time you'll see the zoom is AFTER you fire the shutter and it displays the image to fill that 2.5" or 3.0" inch lcd you have! (or even 2.0") So where does the FF excel? you place 2 cameras exactly side by side of each other, same focal length, same focus point. Same lens. Through the Viewfinder, you'll see the nice Bokeh of your subject on BOTH cameras, exactly the same. Difference? the FF has more frame coverage! Thus, having better "DOF" (or lack thereof) because of the more frame coverage! On this note, let's all by Hasselblad's Medium FF and get some nice digital backs! ;)
haplo602 - Tuesday, April 22, 2008 - link
Hmm ... In my understanding the difference in FF to APS-C is CROP.A 50mm lens on APS-C has the same DOF, same perspective characteristic as on a FF camera, but the sensor is smaller, so you basicaly get a CROP of the original FF image. There is only a perceived zoom effect as the image is a smaller area.
For Nikon you get 1.5x smaller image area, but everything else is the same as on FF.
melgross - Tuesday, April 22, 2008 - link
It has to do with distance from the subject as well. Perspective is the ratio of the distance to the subject to the distance to the background.So, to get the same size on sensor, with the same lens length, you must either move closer, or further, changing the perspective, and the depth of field.
finbarqs - Monday, April 21, 2008 - link
Medium Format* sorry, typo :)Johnmcl7 - Monday, April 21, 2008 - link
Other way round - a larger sensor gives you *less* depth of field which as you quite rightly point out is a strong advantage of a larger sensor.John
pinto4402 - Monday, April 21, 2008 - link
DOF is also a function of the lens. Some ultra-serious photographers are willing to pay $2500 for a Canon 85mm 1.2L over a 85mm 1.8 (which is just as sharp and which only retails for $300), because the 1.2L has a softer, more pleasing DOF effect.TETRONG - Monday, April 21, 2008 - link
Cool article.Looking to buy a camera pretty soon here.
What do you folks think about the G9?
Is there a particular brand I should favor?
Also, are there any cameras available that do "tricky" stuff, like Infrared, Macro, or that neat effect when cities look miniature? (Can't find an example)
I read an article about a guy a few years back that would setup a scene, then he would walk around selectively lighting certain aspects in trippy ways to make a final composite image.
Anyone know what this is called, or where I can learn more about it?
Much obliged!
strikeback03 - Tuesday, April 22, 2008 - link
Is "fisheye" what you are looking for for the miniature cities?and the selective lighting is often called "Painting with light"
plenty of compact cameras can do OK macro if you can get really close to your subject, but as this is often hard for reasons of lighting and/or scaring off the subject, an SLR with a real macro lens is still beneficial.
pinto4402 - Monday, April 21, 2008 - link
There was an article at http://www.popphoto.com/popularphotographyfeatures...">http://www.popphoto.com/popularphotogra.../4923/th...about infrared photography. It also discusses a company that is modifying certain digital cameras for infrared use.