Digital Photography from 20,000 Feet
by Wesley Fink on September 25, 2006 12:05 AM EST- Posted in
- Digital Camera
Lenses on Digital SLR Cameras
While digital point-and-shoot makers normally quote their lenses in familiar 35mm terms, no such convention exists in the digital SLR market. Here, everything is the opposite, as all specs are defined in 35mm terms even though the digital SLRs themselves use a smaller APS C size sensor. This is even carried so far as using 35mm equivalents to define lenses designed for the Digital SLR - even though the "digital-design" lenses can't even cover the frame on a full-size 35mm camera. Thus lenses like the common 18-55mm Canon and Pentax kit zooms and the 18-70mm Nikon and Sony (Minolta) kit zooms really describe those lenses as if they were 35mm.
To know what a lens can do on a digital SLR you have to know the lens factor. Nikon, Pentax, Sony, Minolta, Samsung (Sony sensor) and most others use a sensor about 23.6 x 15.8mm with a lens factor of 1.5. This means that if you multiply the stated lens focal length by 1.5 you will get a focal length of how that lens behaves on your Digital SLR. Let's see how that translates.
Canon uses a CMOS sensor that is slightly smaller at 22.1x14.8mm, and therefore requires a slightly higher 1.6 lens factor. This makes a slight difference in the real focal length of the lens on a digital SLR, but both 1.5 and 1.6 factors are close in value.
Olympus has taken a totally different approach to the sensor used in their digital SLR cameras and has adopted a new digital-only lens mount and lens system called the four thirds system. There is a consortium of 4/3 members that support the 4/3 standard. They include Kodak, Fujifilm, Leica, Panasonic, Olympus, Sanyo, and Sigma. Olympus introduced the first 4/3 system camera and lenses in 2003. Panasonic recently added their own 4/3 camera in the Lumix L1, along with several Leica 4/3 lenses.
It should also be mentioned that Canon has introduced a professional and a premium grade full-frame digital SLRs. There is no lens factor required for these SLRs with a 35mm-size CMOS sensor. These two cameras are, however, in a different category, with the EOS 1DS Mark II selling for about $8000 and the newer EOS 5D for about $3300. Nikon, another recognized top pro brand, has stayed with the DX/APS size sensor in their top pro camera, the Nikon D2X.
Technology has certainly reached the point where 35mm size sensors could be manufactured for a relatively reasonable cost; however, there is no clear movement at the present time to a 35mm size sensor. Most in the industry seem content with the APS C to DX size digital sensor. Perhaps in the near future, we may see some movement to full-frame sensor for the top Pro cameras with APS C/DX for mainstream SLRs. It's just a bit too early to do anything but speculate at this point.
Lens Angle of View
Now that you have a good idea of how to figure out lenses on digital SLR cameras, it is worthwhile to remember why we change lenses.
Wide angle, normal and telephoto lenses see different points of view as you can clearly see in this same scene taken with 35mm, 70mm, and 105mm lenses on 35mm film. From the chart above you can see this would be equivalent to 23mm, 47mm, and 70mm lenses designed for 35mm photography and shot on a Nikon or Sony (1.5 factor) digital SLR. This is a very important distinction and critical to understanding how 35mm lenses behave on today's digital SLR cameras. A 28mm lens designed for a 35mm camera "sees" as if it is a normal lens on a digital SLR, a 50mm normal lens "sees" like a 75mm short telephoto (portrait) lens on a digital SLR. Zoom lenses have been around for quite a while now and most will be familiar with the different view captured with each type of lens. However, they may be surprised to find that the 28mm-80mm wide-angle to short telephoto kit lens they bought for 35mm "sees" like a normal to medium telephoto 42mm-120mm lens on the digital SLR. That is why the new kit lenses that sound so exotic like the 18-55mm and 18-70mm are nothing more than the APS C size version of the old reliable 28-80 and 28-105.
Once you get accustomed to the new focal length definitions for digital SLR cameras, things will fall into place. The shorter the focal length the more extreme the wide angle and the larger the "view" included in the image. The larger the focal length value the more "magnified" the image. Wide angle ranges are very useful for interiors and shots of groups of people. Telephotos are great for shooting from an audience or nature photography like birds. Normal of course is a good all-around focal length.
Because existing 35mm lenses make up the bulk of available lenses on digital SLR cameras, and because the real lens value is a multiple of 1.5 or 1.6, it is easy to see that wide-angle lenses are hard to find on digital SLRs. The 35 wideangle 28mm is a normal lens on a digital SLR, and the super-wides usually stop at specialty fisheye lenses around 15mm, which is still a normal wide 23 to 24mm on digital SLR cameras. As a result, almost any extreme wide-angle lenses you will find for digital SLR cameras will be designed just for digital cameras. These include the Sigma and Tamron lenses in the 10-20mm range, and lenses from the major lens makers like the Nikon 11-18mm.
The Olympus four thirds system lens factor is included mostly for reference, since Olympus manufactures a whole new lens line for their digital SLR. None of the older Olympus lenses from 35mm work on the new digital cameras unless you use a special converter. Even with the converter they will work in full manual mode only. The 2.0 lens factor does come into play for third-party lenses designed to work on the Olympus 4/3 cameras, so you can determine the effective focal lengths with the 2.0 multiplier. However, independent lens makers are mainly designing for a 1.5 to 1.6 lens factor, and the 4/3 equivalents are not always very attractive. Sigma markets basic and specialized fast digital lenses in the 18-55mm range. That's a desirable 27/29 to 83/88 on a 1.5 or 1.6 camera. However, on Olympus 4/3 that is a 36-100mm lens. That is still useful, but there is almost no wide-angle when mounted on a 4/3 camera. This is the problem Olympus faces. Until others adopt this open standard four thirds mount, the only lenses designed specifically for the 4/3 system will come from Olympus.
It should now be clear why the digital SLR, with the ability to see through the taking lens, is a more flexible platform for digital photography. Today's Digital SLRs focus and meter exposure through that same taking lens. With auto-exposure and autofocus, a digital SLR can be as simple as any point-and-shoot camera. Plus there is the added flexibility of a much larger selection of interchangeable lenses that are available to allow the user the best chance to capture what they want in any situation. However, despite the fact you don't need to know anything about F-stops, shutter speed, and the light sensitivity of the sensor, we will tell you with absolute certainty that you will take better images if you do understand a bit about what is going on behind those automatic functions.
While digital point-and-shoot makers normally quote their lenses in familiar 35mm terms, no such convention exists in the digital SLR market. Here, everything is the opposite, as all specs are defined in 35mm terms even though the digital SLRs themselves use a smaller APS C size sensor. This is even carried so far as using 35mm equivalents to define lenses designed for the Digital SLR - even though the "digital-design" lenses can't even cover the frame on a full-size 35mm camera. Thus lenses like the common 18-55mm Canon and Pentax kit zooms and the 18-70mm Nikon and Sony (Minolta) kit zooms really describe those lenses as if they were 35mm.
To know what a lens can do on a digital SLR you have to know the lens factor. Nikon, Pentax, Sony, Minolta, Samsung (Sony sensor) and most others use a sensor about 23.6 x 15.8mm with a lens factor of 1.5. This means that if you multiply the stated lens focal length by 1.5 you will get a focal length of how that lens behaves on your Digital SLR. Let's see how that translates.
| SLR Lens Factor Conversions | |||
| 35mm Focal Length | 1.5 Lens Factor Nikon, Pentax, Sony, Minolta, Samsung |
1.6 Lens Factor Canon |
2.0 Lens Factor Olympus |
| 10-20mm | 15-30mm | 16-32mm | 20-40mm |
| 14-45mm | 21-68mm | 22-72mm | 28-90mm |
| 18-55mm | 27-83mm | 29-88mm | 36-110mm |
| 18-70mm | 27-105mm | 29-112mm | 36-140mm |
| 24 mm | 36 mm | 38 mm | 48mm |
| 28 mm | 42 mm | 45 mm | 56mm |
| 35 mm | 53 mm | 56mm | 70mm |
| 50 mm | 75 mm | 80 mm | 100mm |
| 85 mm | 128 mm | 136 mm | 170 mm |
| 70-210mm | 105-315mm | 112-336mm | 140-420mm |
| 135 mm | 203 mm | 216 mm | 270 mm |
| 75-300mm | 113-450mm | 120-480mm | 150-600mm |
| 500 mm | 750 mm | 800 mm | 1000 mm |
Canon uses a CMOS sensor that is slightly smaller at 22.1x14.8mm, and therefore requires a slightly higher 1.6 lens factor. This makes a slight difference in the real focal length of the lens on a digital SLR, but both 1.5 and 1.6 factors are close in value.
Olympus has taken a totally different approach to the sensor used in their digital SLR cameras and has adopted a new digital-only lens mount and lens system called the four thirds system. There is a consortium of 4/3 members that support the 4/3 standard. They include Kodak, Fujifilm, Leica, Panasonic, Olympus, Sanyo, and Sigma. Olympus introduced the first 4/3 system camera and lenses in 2003. Panasonic recently added their own 4/3 camera in the Lumix L1, along with several Leica 4/3 lenses.
It should also be mentioned that Canon has introduced a professional and a premium grade full-frame digital SLRs. There is no lens factor required for these SLRs with a 35mm-size CMOS sensor. These two cameras are, however, in a different category, with the EOS 1DS Mark II selling for about $8000 and the newer EOS 5D for about $3300. Nikon, another recognized top pro brand, has stayed with the DX/APS size sensor in their top pro camera, the Nikon D2X.
Technology has certainly reached the point where 35mm size sensors could be manufactured for a relatively reasonable cost; however, there is no clear movement at the present time to a 35mm size sensor. Most in the industry seem content with the APS C to DX size digital sensor. Perhaps in the near future, we may see some movement to full-frame sensor for the top Pro cameras with APS C/DX for mainstream SLRs. It's just a bit too early to do anything but speculate at this point.
Lens Angle of View
Now that you have a good idea of how to figure out lenses on digital SLR cameras, it is worthwhile to remember why we change lenses.
Wide angle, normal and telephoto lenses see different points of view as you can clearly see in this same scene taken with 35mm, 70mm, and 105mm lenses on 35mm film. From the chart above you can see this would be equivalent to 23mm, 47mm, and 70mm lenses designed for 35mm photography and shot on a Nikon or Sony (1.5 factor) digital SLR. This is a very important distinction and critical to understanding how 35mm lenses behave on today's digital SLR cameras. A 28mm lens designed for a 35mm camera "sees" as if it is a normal lens on a digital SLR, a 50mm normal lens "sees" like a 75mm short telephoto (portrait) lens on a digital SLR. Zoom lenses have been around for quite a while now and most will be familiar with the different view captured with each type of lens. However, they may be surprised to find that the 28mm-80mm wide-angle to short telephoto kit lens they bought for 35mm "sees" like a normal to medium telephoto 42mm-120mm lens on the digital SLR. That is why the new kit lenses that sound so exotic like the 18-55mm and 18-70mm are nothing more than the APS C size version of the old reliable 28-80 and 28-105.
Once you get accustomed to the new focal length definitions for digital SLR cameras, things will fall into place. The shorter the focal length the more extreme the wide angle and the larger the "view" included in the image. The larger the focal length value the more "magnified" the image. Wide angle ranges are very useful for interiors and shots of groups of people. Telephotos are great for shooting from an audience or nature photography like birds. Normal of course is a good all-around focal length.
Because existing 35mm lenses make up the bulk of available lenses on digital SLR cameras, and because the real lens value is a multiple of 1.5 or 1.6, it is easy to see that wide-angle lenses are hard to find on digital SLRs. The 35 wideangle 28mm is a normal lens on a digital SLR, and the super-wides usually stop at specialty fisheye lenses around 15mm, which is still a normal wide 23 to 24mm on digital SLR cameras. As a result, almost any extreme wide-angle lenses you will find for digital SLR cameras will be designed just for digital cameras. These include the Sigma and Tamron lenses in the 10-20mm range, and lenses from the major lens makers like the Nikon 11-18mm.
The Olympus four thirds system lens factor is included mostly for reference, since Olympus manufactures a whole new lens line for their digital SLR. None of the older Olympus lenses from 35mm work on the new digital cameras unless you use a special converter. Even with the converter they will work in full manual mode only. The 2.0 lens factor does come into play for third-party lenses designed to work on the Olympus 4/3 cameras, so you can determine the effective focal lengths with the 2.0 multiplier. However, independent lens makers are mainly designing for a 1.5 to 1.6 lens factor, and the 4/3 equivalents are not always very attractive. Sigma markets basic and specialized fast digital lenses in the 18-55mm range. That's a desirable 27/29 to 83/88 on a 1.5 or 1.6 camera. However, on Olympus 4/3 that is a 36-100mm lens. That is still useful, but there is almost no wide-angle when mounted on a 4/3 camera. This is the problem Olympus faces. Until others adopt this open standard four thirds mount, the only lenses designed specifically for the 4/3 system will come from Olympus.
It should now be clear why the digital SLR, with the ability to see through the taking lens, is a more flexible platform for digital photography. Today's Digital SLRs focus and meter exposure through that same taking lens. With auto-exposure and autofocus, a digital SLR can be as simple as any point-and-shoot camera. Plus there is the added flexibility of a much larger selection of interchangeable lenses that are available to allow the user the best chance to capture what they want in any situation. However, despite the fact you don't need to know anything about F-stops, shutter speed, and the light sensitivity of the sensor, we will tell you with absolute certainty that you will take better images if you do understand a bit about what is going on behind those automatic functions.
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sliver1 - Tuesday, September 26, 2006 - link
Nice wrapping article! There is one thing that doesn't fit though...If you're a pro photographer, then you don't need such a website to learn about photography or entry-level consumer DSLR cameras. A thing like "a good auto white balance" doesn't mean anything since pros are shooting RAW anyway. Also, you don't embrace a "camera system" solely for the body and the lenses -- there are lots of other accessories required that may not be available or as good as those of the two major players with offerings from other companies. (Have you heard of pro photographers working with anything but Canon or Nikon?)
On the other hand, yes, other websites prepare extensive reviews that cover, among other things, startup times, location of mirror lockup or second curtain sync features, discuss MTF charts and review lens by talking about chromatic aberrations/distortion/corner softness, etc. -- all sort of things that that matter to pros, even if it won't be covered on this site.
Where does that leave this new Anandtech section? Inevitably to consumer or photo hobbyists/enthusiasts. This is for people who expect better image quality and more freedom in picture taking than what a point-and-shoot can offer -- yet not being anywhere near pro.
So as long as you stick with this segment, spend paragraphs talking about the "direct print" features, discuss "picture styles", explain the effective range of the built-in snap-up flash, then okay. But it would be ridiculous to write articles about top of the line cameras like the Canon 5D, Canon 1DsMkII, Nikon D2xs, etc., as much as it would be ridiculous to talk about thousand dollar pro lenses, etc.
While I'm at it...
1) You seem to believe that the crop factor has an influence on the "rule of thumb" for handheld shots. A 50mm lens, equivalent to a 80mm on a 1.6x crop, still has a "rule of thumb" of 1/50s. Keeping only a smaller part of the image circle does not lengthens a lens, does not add vibration...
2) Image Stabilisation (IS) is very handy (no pun intended), but cannot replace a faster lens. Even if you can shoot handheld 3 stops slower (or even 4 stops, as in the new Canon EF 70-200mm f/4L IS USM), this won't help for a moving subject, and you may well end up with blurry pictures after all -- especially if you're shooting people/animals...
3) You seem to diminish/discard the importance of a full-frame sensor. A full frame sensor has a dramatic impact on the quality of the images, especially because of lower pixel density. Also, the only comparison you've mentionned for film vs digital left readers to think that digital still had something to envy film -- which is really not seeing the whole picture. Digital reduced noise (grain) dramatically. It has been reported by more than a serious source that a 1DsMkII has more resolving power than *medium format film*. Color rendition is better in digital by *far*. More control over the whole workflow. All in all, digital is winning easily, which is why pros are all going digital and companies are giving up film. The only drawback is the higher initial cost.
And finally...
4) No pro relies on full-auto settings in a camera, no matter how sophisticated it is (or will become). Even if technology (what this website is about) keeps bringing tools to facilitate the photographer's job and render sharper, cleaner images, etc., that's not what makes a picture compelling. A 39MP PhaseOne digital back won't do any good in the hands of a beginner, as much as a pro could make astounding pictures with a very modest camera... So, please make sure you don't play the marketing game companies are using to have consumer believe they can make wonderful pictures with the touch of a single button ;)
silver - Tuesday, September 26, 2006 - link
" It has been reported by more than a serious source that a 1DsMkII has more resolving power than *medium format film*. Color rendition is better in digital by *far*. More control over the whole workflow. All in all, digital is winning easily, which is why pros are all going digital and companies are giving up film. "Not at all ! Pro's jumped on digital as it speeds up their entire workflow and is more effecient than film. It reduces costs significantly as most studios have film processing and proofing costs around $4,k~$5,k per month. Also having the image immediately available to the client has huge returns in sales points. These are trully the only reasons. Film is still far and away better when comparing apples-to-apples.
sliver1 - Tuesday, September 26, 2006 - link
As others have said it, at this point, there would be endless arguing about digital vs film, and I understand that some could still want to use film for obscure/critical reasons, such as shooting in harsh -60 celcius north pole conditions. ...But seriously, what I was simply trying to point out, though, is that the only mention of "film" in the article was an argument in favor of film, which doesn't allow to see the whole picture.As for why pros are switching to digital... If it was only a matter of saving on the studios' workflow, or speeding things up for photojournalists, then only some fields of photography would have made the switch. Many other pros -- in landscape photography, for example, where you can get very complex histograms pushing the range to its limits -- would have stuck to film. The fact is that they are all switching.
http://www.luminous-landscape.com/reviews/shootout...">http://www.luminous-landscape.com/reviews/shootout...
silver - Tuesday, September 26, 2006 - link
I can honestly say I don't know a single photographer shooting quality landscapes on digital. I certainly don't know any that would bother with purchasing a a $33,000 Phase One digital back for a medium format camera when a $1.00 sheet of film in a 4x5 will best it in color and tonal scale.http://www.calumetphoto.com/item/PE71278.html">http://www.calumetphoto.com/item/PE71278.html
Visual - Tuesday, September 26, 2006 - link
this is a topic with no definite outcome yet. you two can argue all you want, but especially with the nicknames you've got here it'll just look stupid ;)silver - Tuesday, September 26, 2006 - link
Who's arguing ? Digital has progressed to being nearly as good as 35mm but there is no solid documetation that I've read stating that its level of quality up to 6x4.5cm, 6x7cm, 6x9cm format film cameras.As to why pro's switched to digital, it's beyond dispute. Dollars make sense. Money talks and film took a walk. It's really that simple. Pro's have one and only one job : making money. If the quality of 8MP digital is adequate to the masses then that is what they will shoot. It doesn't matter if Mamiya has a 22MP or that you can get a $30,000 Phase One digital back for your Hasselblad. Pro's will use what is deemed acceptable or necessary by the client and that's all there is too it.
Resh - Tuesday, September 26, 2006 - link
Hate to fan these flames as this is ultimately a useless discussion, but here are some resources:http://www.luminous-landscape.com/essays/back-test...">http://www.luminous-landscape.com/essays/back-test...
http://www.luminous-landscape.com/essays/Cramer.sh...">http://www.luminous-landscape.com/essays/Cramer.sh...
N
silver - Wednesday, September 27, 2006 - link
LOL ! Hopefully you don't consider Michael Reichmann and Co. to be professionals !!!!Please, take a look at the following :
http://www.montezucker.com/">http://www.montezucker.com/
http://mattkim.com/">http://mattkim.com/
http://www.clayblackmore.com/">http://www.clayblackmore.com/
http://www.cantrellportrait.com/">http://www.cantrellportrait.com/
http://www.silvermanstudio.com/">http://www.silvermanstudio.com/
http://www.lionphotography.com/">http://www.lionphotography.com/
http://www.orangeexposure.com/">http://www.orangeexposure.com/
http://www.mattramosphotography.com/">http://www.mattramosphotography.com/
http://www.ftapia.com/">http://www.ftapia.com/
http://www.gordonmgrant.com/">http://www.gordonmgrant.com/
Yeah, these are PRO's who WORK in the field of photography ! And note that most of them don't even use the words "film" or "digital". They simply don't care what the tool is. They have a job to do and that job is to use their talents to make money. Short and simple. Digital is to the working pro as tires are to the rims on your car : a perfect fitting necessity.
wheel - Monday, September 25, 2006 - link
Hi,I am a big computer enthusiast, overclocker, IT professional and long time Anand Tech reader (since inception?) I also have been into amateur photography for about 7 years, recently switching to digi SLR about 14 months ago. All my knowledge is self taught from reading stuff on the web and my own experimentation. I use 6 lenses and have taken around 12,600 photos with my SLR camera in the time that I have owned it! (just providing a gauge of my photographic experience and enthusiasm)
I was very disappointed with this article! Firstly because it degraded other excellent websites while simultaneously borrowing content and images from them! And secondly from a technical point of view I disagreed with some of the assertions made.
What you correctly identified in your article was the flexibility of an SLR camera. However you also said a few separate times that comparing times including power-on time had now become irrelevant because they were all pretty fast? I disagree!
One use of an SLR camera is sports or action photography where start up times can be very important. Just this weekend I took pictures at a car rally, where on one day it rained heavily and on another it was very dusty. I held my camera under my jacket and only pulled it out and turned it on at the last minute so to keep it from getting too wet. I think the 350D is 0.2 seconds start up time which is fine for this use, but I would not consider a camera that forced the user to wait for much longer (for example if it needed to clean the sensor). The nature of sports photography demands more of the performance of the camera as interesting things may suddenly unfold so the performance of the camera and the ability to change settings quickly rather than navigate menus gains importance...
I think DPReview and Steves Digicams both understand that their readers may vary significantly in what they want from a camera - that is in part why they may be seen as ambiguous in their conclusions as they avoid giving cameras an overall score like 88% etc. That they cover a many technical details in the article allows the readers to decide what features are important and reach their own conclusions.
Another thing you wrote was that there weren't many positive things about zoom lenses. I have both zooms and prime lenses and appreciate that they both have strengths and weaknesses.
You also said "Canon and Nikon still make reasonable 50mm f/1.8 lenses, which also happen to be the sharpest lens in either lens lineup." Can you qualify this statement re: sharpness? The Canon 50mm 1.8 lens is cheap and pretty good but not a silver bullet. The 50mm f/1.4 beats it in all areas and is still quite reasonably priced. And of course I am sure the 50mm f/1.2 is excellent, although very expensive.
So I am sorry but I think you should have a little more respect for the established sites who have done a fantastic job over the years in the field that they specialise in. I shall read your reviews in parallel with the established camera sites but will take your opinions with a grain of salt!
For others interested in digital SLR photography I recommend the following websites:
Body reviews:
http://www.dpreview.com/">http://www.dpreview.com/
http://www.steves-digicams.com/">http://www.steves-digicams.com/
http://www.luminous-landscape.com/">http://www.luminous-landscape.com/ (also general info and lens reviews too)
Lens reviews:
http://www.fredmiranda.com/reviews/">http://www.fredmiranda.com/reviews/
http://www.slrgear.com/reviews/">http://www.slrgear.com/reviews/
http://photosig.pcphotoreview.com/">http://photosig.pcphotoreview.com/
Cheers,
Ian
Wesley Fink - Tuesday, September 26, 2006 - link
It was not my intent to degrade other excellent photo websites, in fact I mentioned no site specifically in my introductory guide. You obviously appreciate the level of some the more technical digital review sites and I certainly can appreciate where you come from. As I have stated several times, we do not want to try to emulate those sites, but to try to chart our own style. We also will not please everyone with our approach.Where we have used images that are not public domain we have attributed those images to their sources in the guide. This is an introductory guide, and not a review.
Photodo is the well-respected Swedish lens data/review site that was extablished by Lars Kjellberg and is now owned by ePHOTOzine. The Nikon AF 50mm f1.8D is rated a Photodo MTF of 4.4, while the more expensive f1.4 is rated a 4.2. The Canon 50 EF 50mm f1.8 II costs $70 and is rated a Photodo MTF of 4.2, while the earlier 50 F1.8 is rated 4.4. The $350 Canon EF 50mm F1.4 is also rated at 4.4. All 5 of these lenses are among the highest MTF rated Canon and Nikon lenses you can buy, and all significantly outperform most zoom lenses in either line. The Canon 50f1.8 at $70 is a stellar value, at half a stop slower than the 1.4 and 1/5 the price. The plastic lens mount on the II version is cheesey, but owners have not complained about durability issues.