What makes a lens digital?

[mksnowhite]

This may sound like an obvious question...but other than the lack of aperture

ring? I have 70-300 with no ring and it's a G lens (actually it is a useless

lens)...won't work on my 8008...but yet it is not a digital lens, but works on

my digital Nikons just fine.

 

So...is the focal length of a digtal lens true to what it says it is...or do we

have the crop factor? I have the following lenses: 12-24 f4, 28-70 2.8, 70-200

2.8 vr, 300 f4, 50 1.8 and 85 1.8. There are times when the 20-70 is too wide

as it isn't a true 28...so was thinking of selling the 12-24 and buying a 17-

55. Will I be getting a true 17-55 or a 32-70 something (I'm terrible at math.

I like the bigger paerature of the 17-55 over the 12-24. If there is a crop

factor why bother calling it a digital lens and not a G lens. What am I missing?

 

TIA

[Michael R Freeman]

"So...is the focal length of a digital lens true to what it says it is..."

 

Yes. 17mm is 17mm is 17mm. But when *compared to 35mm*, the field of view on a DSLR of a 17mm lens will be roughly equal to the field of view of a 25mm lens mounted on a film body.

 

A "digital" lens is one that is only intended for use on a Nikon DSLR, and is designated "DX Nikkor". These lenses will mount and work on film bodies (including the 8008), but the image circle is too small to cover the full 35mm format.

 

BTW, the 70~300mm G lens *will* work on your N8008 in P and S modes.

[photo5]

They all have the crop factor as far as I've seen. The 17-55 will become a 25.5-80 or thereabouts.

 

Dave

[juanjo_viagran]

AF-D Introduced in 1992. AF Nikon lenses with a CPU that also relays distance information to the camera, most useful for ultra-precise TTL flash. Among the first were the 35-70mm f/2.8D AF and 80-200mm f/2.8D ED AF Nikkor.

AF-I Introduced in 1992. Nikon lenses with a coreless Integrated motor for faster AF in high-end telephoto lenses. The first were the 300mm f/2.8 and the 600mm f/4, both D ED IF AF-I.

AF-S Introduced in 1996, Nikon lenses with a "Silent Wave" ultrasonic motor of their own, for fastest AF operation. The first were the 300mm f/2.8, 500mm f/4 and 600mm f/4, all D ED IF AF-S Nikkor.

G Introduced in 2000. Nikon AF-D lenses without aperture ring. Need to be controlled through the body dials of latest cameras. The first was the 70-300mm f/4-5.6G AF.

VR Introduced in 2000. Nikon lenses with a Vibration Reduction system allowing for crisp images handheld at very slow shutter speeds. The first was the 80-400mm f/4-5.6D ED VR Zoom Nikkor.

DX Introduced in 2003. Nikon G lenses designed to just fill the frame of the DX format APS-C sensor size used in Nikon D-Series SLR cameras. The first was the AF-S DX 12-24mm f/4G IF-ED Nikkor.

[georges_pelpel]

The coverage/view angle of the lens makes it a 'digital'. It is actually a gimmick. Most

digital sensors (all Nikon one) are smaller than a 35mm film area. As a result the lens

doesn't have to cover such a large area (24mm x 36mm) and can be made smaller and

lighter, thus the DX (digital) line. The DX lenses won't work on a film camera as they

cannot cover the full image without having black corners, all other lens will work on any

camera, film or digital. So the 'digital' (DX) is a fancy gimmick that actually says the lens

has a more limited range.

Another result of the smaller size sensors is that the lens says the real focal but not the

familiar angle of view. A 50mm is a normal lens on a 35mm film camera but becomes the

equivalent of a 75mm on a DSLR, or the equivalent of a 17mm on a 4x5 film camera.

All Nikon DSLR have a 1.5x focal increase, so a 12mm is the equivalent of a 18mm, and a

50mm is the equivalent of a 75mm.

Note that the Nikon terminalogy for lenses made for the digital sensor coverage is DX. The

G terminalogy is for lenses that do not have the apperture ring. A G lens can be DX or not.

As an example your 12-24 is both DX and G and will only cover the digital sensor, on the

other hand your 70-200/2.8 is a G lens but not DX meaning that it can be used on any

camera, film or digital.

Hope I am making myself clear.

[nick_evans1]

Hi

Nikon G Series of lenses are not digital exclusive, they came out and are designed to be used with cameras that have two command dials like the F5, F6 and the digital bodies.

 

You can use it on your 8008 (801) but you have toi use the camera in Shutter Priorty mode (select shutter speed, camera select aperture)

 

True digital lenses are designed to take into account the 'crop factor' that you find on Nikon digi bodies and it is the 'DX' range hence a 12-24 lens is roughly 24-50 equivilent on a 35mm machine.

 

As the CCD chip is smaller than 35mm film these lenses are designed to focus you image on to the chip so if you could use them on a 35mm camera they would only cover a small area of the film

 

As for the 70-200 and 300mm lenses you will find that they are work out to be roughly 140-400 & 600 when used on a digi body.

 

Hope this make sence

 

Nick

[iancoxleigh]

Nick, you have your numbers out of whack a bit. The 12-24 offers a field of view equivalent to 18-36 on a 35mm plane. A 300 becomes roughly 450 (not 600). It is a 1.5 crop factor.

 

And for Melanie, the simple answers are:

 

1. A Digital "DX" lens is identified as such because it won't cover a full frame (35mm) place with its image circle and can only be used fully on a DSLR with a 1.5 crop factor. However, note that I said 'can't be used fully' -- the 12-24 will actually cover the full 35mm from 18mm to 24. Plus, you could always crop you film images down to the 1.5 factor.

 

2. The remain question I have no answer to. Why isn't a "DX" lens marketed with what its EQUIVALENT focal length (since you can't actually use it to get its true focal length most of the time)? I would think marketing 105-450 DX zoom (not that there is a DX 70-300 -- but if there was) would be more attractive at the long end.

[mksnowhite]

Wow thanks for the responses. yes it is more clear now...and does seem a bit gimcky so I'll stick with what I have! I get a lot of distortion in the 12-24 though....so was figuring it had to be a "true" 12

[bjørn rørslett]

The designation for the lens (such as 'DX' or 'DG' or similar) makes it "digital". Period. The "digital" feature falls into the same category as "Macro", meaning it is just a means to make people believe they get something they won't get, and still consider it worth the price. Marketing hype in other words.

 

Focal length never change with format, so your 12 mm is really 12 mm. Period.

 

Many people these days never have shot with a 35 mm camera, so the infamous "crop factor" is losing the last vestiges of its value as a reference anyway.

[timberwulf]

I don't feel that DX is a "gimmick" at all. Yes, it will not work on your film cameras, however, the smaller image circle also means a lower build cost, allowing someone who doesn't need that lens to work on a film camera to get more gear for their money. :)

[gary_wong2]

After reading all these posts, is this a true statement?

If the focal lengths are the same, a digital lens will project a cropped (not reduced) image when compared to the image projected by a regular (non-digital) lens.

 

If this is true, does this apply to all lens manufacturers, Canon, Sigma, Tamron?.?

[bjørn rørslett]

The focal length of a lens dictates the magnification of image detail, it has nothing to do with the size of the projected image circle. So saying a lens projects a "cropped" image is basically meaningless.

 

The real story behind the DX lenses is that Nikon found it necessary to make a series of telecentric lenses for thir DSLR models. Now, "telecentric" isn't something you would label your products with since just a handful of people understand what is meant and why it is so important. So enter the catch-phrase "digital" instead.

 

A telecentric design means the projected image rays exit almost in parallel thus have nearly 90 degrees of incidence to the imager surface, this reduced corner fall-off and improves photon capture efficiency of the photosites. Although most people consider "DX" to mean a smaller image circle, the fact is that several of these lenses can be used to some extent on 24x36 mm cameras as well. All DX Nikkors I've tested have shown a telecentric behaviour.

[studor13]

Dr Rorslett, the one thing I wish you would add/address is the effect of the DX lenses for better controlling Chromatic Aberration (CA). As I understand it, it is the ED element(s) plus the telecentric design which reduces the problems associated with CA. For example, I have almost no CA problems with my 18-70DX, but have an awful time with the 35m f2 AIS on a D70.

[steve_larese1]

Related explanation :)

 

http://www.digitaldarrell.com/DDBlog-ShouldNikonMakeA35mmSizedSensor.asp

[frank uhlig]

What makes a lens "digital" is the same that makes a tripod "digital", or a camera bag "digital":

 

ADVERTISEMENT savvy, nothing else except for two tiny thing with some digital lenses:

 

Some are expressly designed to illuminate only a smaller circle than 35mm film lenses (smaller sensors geometry); and some are designed to fit the sensor physics better than a film lens would (sensors like vertical hitting light, not angled; film seems not to mind slanted light).

And some D lenses take care of both changes.

 

But most film lenses will do ok in digital and vice versa.

 

Advertisement hype is most of this.

[bjørn rørslett]

It's often stated that DX design (i.e. telecentric) largely eliminates CA issues. In practice this is far from the truth. Do remember that telecentricity is only needed for lenses having very wide angle of view, so normal and longer lenses do not benefit from a "DX" design (in fact, a fast 300/2.8 lens will be virtually equal in size be it made for "1.5 crop", 24x36 or 6x6 cm formats). So, it is the wide view that gives potential CA troubles and although a telecentric lens can mitigate that issue, it cannot be elimated by telecentricity alone. That is simply because you need optical correction within an accuracy that is not feasible for an affordable, mass-production lens. When the lens is mounted on a higher resolving camera its weaknesses are more clearly visible, so a lens that gives adequate results wuith a D70 won't necessarily do so on the D2x. The 18-70 DX is a good example, its CA issues are much more visible on the D2X.

[sam_thompson2]

"If this is true, does this apply to all lens manufacturers, Canon, Sigma, Tamron?"

 

The exception is the 4 thirds mount cameras and lenses made by Olympus, Panasonic and Leica.

[tom_jenner1]

Judging by the fact that I can get more than a bivalent light level through my lenses (in fact I get continuously variable light levels)I'd say that they were all analog and not digital :>)

 

Come on, you all knew some smart alec would say that!

[ajzammit]

The focal lenght of lens, which is also written on a lens, is just that ... it's focal lenght. Whether you mount it on a medium format, digital, or 35 mm, its focal lenght WILL ALWAYS BE THE SAME. What changes is the field of view. So, a 12-24 lens mounted on digital will give you the field of view of an 18-36mm on 35mm a cameras irrespective of whether it is a DX lens. In fact, i was reading that people have tested the TOkina 12-24mm on film cameras, and worked lovely (obviously after zooming in to aviod vignetting). If i remember, the lens was zoomed to 18mm.

[gary_wong2]

Yes, the focal lengths are the same between lenses. The purpose of mentioning focal length being equal was merely to make the comparison between the digital and regular lenses 'equal'. I am sure that if did not mention it someone would have mentioned something about the focal length. Anyway, you guys are very techically adept. Much more than I will ever be. I was just looking for a 'yes', 'no' or basic answer to the question.

 

Let's rephrase the question to make it clearer. If the focal lengths are set at 50mm on a digital and a regular (non-digital) lens, a digital lens will project a cropped image when compared to the image projected by a regular lens. Is this true?

[bjørn rørslett]

No, your statement is false. The DSLR Nikon camera will "crop" the projected image, since it has a sensor smaller than the 24x36 format. But the lenses can never know what camera they are attached to. So they always project an image at whatever image circle size their design specifies.

[dbcooper]

Focal length is focal length, and the target area is irrelevant to the focal length. The image circle can change, but it also gets larger when you stop down. There is no 'crop factor' in the lens directly due to the focal length, but there may be due to the lens design.

 

Saying the focal length is different from DX to other lenses is rather like saying there's a difference between f5.6 at 50 or 300mm focal lengths, even though the actual diaphragm opening will be larger in the longer lens, the amount of relative light let in to the target is the same, but there sure is a smaller target in most DSLRs. We just have to all get used to our gear. The whole '1.5x' thing is only a measure of what you'd get with a 35mm film camera vs most Nikon digitals, to give you an idea of what the field of view will be like. A 35mm lens on a 35mm film camera will appear wider than the same lens on a DSLR, and narrower than a 35mm lens on a 6x7cm camera. Most DSLRs are a different format than 35mm film.

 

The DX lenses (this is the Nikon forum, right?) are called 'digital' lenses for two reasons: 1) the smaller size of the sensor means the lenses can be designed for the smaller size target image (digital sensor). That's why we can get an AF 18-200mm DX VR zoom that works great for under $1,000. 2) marketing hype for folks that think they have to use 'digital' lenses on a digital camera (digital tripods, indeed...geez, are some folks really that gullible?).

 

Aperture ring? Who needs one? Use the command dial - it's easier and faster, unless you have two thumbs on your left hand. It's also why G lenses were made that way in the first place...they're supposed to be used on cameras with a command dial. I have the 80-400mm VR zoom, with an aperture ring and all, and it works fine on my Nikon DSLR. Works fine on film bodies, too, but it's slower to operate (I only have one thumb on my left hand). I do lose AF on my FM3A, though. ;)

 

I'm honestly not trying to wind anyone up, but if you own digital Nikon bodies, why bother with 35mm film at all? There's really no advantage to it, except maybe round fisheye shots.

[jack_molle]

I tried a small test. I mounted my D70s on a tripod. I then set the camera mode to "A" and f8. At approximately 20 feet, I took the same picture with an 18-135DX, 28-85AFn, and 18-35D at 35mm. I can compare the result image from the two old AF film lenses and the new DX lens. The resulting images were the same! I assume my digital camera can't tell the difference between an old and newer lens. If I did the same with my film camera, I assume the older lenses would show more image coverage (1.5x) on 35mm film and the DX lens would not "fill" the 35mm film format. So, I am thinking that from a digital camera's perspective, there is no cropping. The sensor just can't "see" the entire image seen by a film camera. I tried other focal lengths and the result is similar (I have other old lenses to compare with the 18-135). What am I missing?

[michael erlich]

There's one more difference on a lens that has truly been optimized for digital:

 

Digital sensors are more reflective than film, so digital lenses have improved coatings on the rear element to minimize light reflecting off the sensor from being reflected back onto the sensor. It's supposed to reduce flare.