The Digital Sensor: A Guide to Understanding Digital Cameras
by Wesley Fink on April 21, 2008 1:00 AM EST- Posted in
- Digital Camera
Field of View
Now that you have some basic understanding of digital camera sensors, it is time to take a closer look at the practical considerations that are created by these differences in sensors. A very poorly understood concept is the lens multiplier with the smaller than 35mm sensor-size that is used in most digital SLR cameras. The best way to illustrate this is with actual photos taken by a range of digital SLR cameras from the same tripod location.
We shot the same view using the exact same tripod location on a range of current digital SLR cameras. Each camera used a lens with the same focal length of 50mm. Lighting was the same with a 100W high-right light source, camera aperture was f4.0 in all cases, and white balance was set to Tungsten. The purpose of this series is to illustrate what you can see with each camera with the same lens, so exposure data is somewhat irrelevant, but exposure conditions were kept as constant as possible for reference.
The Canon EOS 5D is a full-frame SLR, which means the sensor is the same size as 35mm film. This point of view is the way an image at this distance would look on the Nikon D3, Canon 1Ds III, Canon 5D, and 35mm film cameras. The APS-H sensor used in a few Canon pro models is 1.3X and falls between full frame and 1.5X in its field of view.
The 1.5X multiplier is typical of cameras based on the Sony and Samsung sensors. This includes the Sony A700/A350/A300/A200/A100, the Nikon D300/D200/D80/D60/D40x/D40, the Pentax K20D/K10D/K200D/K100D, and all Samsung digital SLRs.
Canon introduced the small APS C sensor in the pioneering D30 and they have kept this size for consumer cameras since. This field of view is typical of the Canon 40D/XTi/XSi. The Foveon sensor Sigma SD14 has a 1.7X lens multiplier and falls between this small APS C Canon sensor and the 4/3 system.
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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.