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Crop Factor with Digital Lenses

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debjg

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Regarding lenses specially being made for digital now ... does this negate the crop / magnification factor that usually comes into play when using a 35mm lens with a digital sensor? Is a 50mm view through a DG lens on a digital camera the same as a normal 50mm lens on a 35mm camera? Or does 'specially created for digital' simply mean they've taken steps to correct vignetting, purple fringing and other such effects?
 
A 17~55mm lens (for example) has a focal length of 17~55 regarless of the camera body. DX, or cropped, means the image it produces will cover an APS-sized frame but will not cover a 35mm frame. By making it a DX lens it can be smaller than the same focal length (and optical quality) lens would need to be on a film camera or FF camera.
 
Matt_Anderson said:
and you get short changed on the DOF,
Click to expand...
True, but your reasonably priced 200mm acts like a more expensive 300mm, the one my wife won't let me buy.
 
That's not true. The view is the same whether you have a 50mm DX or a 50mm non-dx attached. In both cases it looks like the equivalent FOV of a 75mm lens (assuming 1.5x crop factor sensor as nikon uses) on a 35mm film camera or FF digital.

Someone else made a comment on DOF. I don't think you get short changed. That might be the point of view of someone who wants less DOF, but some people want more DOF.

In other words, if you want more telephoto and DOF for your money, then DX is good. However, if you want more wide angle and less DOF for your money, then FF is good.

The arguments about whether one is better or not assume that the two different size sensors have close to the same number of pixels. If, on the other hand, you had a FF sensor that had the same pixel density as the DX sensor, then the FF sensor would be better because you could always crop the FF down to DX size and have the same exact image as you would have had with the smaller DX sensor.
 
Focal length is focal length. A 12-24mm is still a 12-24mm, whether it is a made for digital or not. The difference is a full frame lens is designed to spread the image over a larger area. Heavier and more expensive than designing a smaller lens that only covers a smaller area. Generally speaking this could make it smaller, less expensive, and sometimes sharper.

A 12-24mm, because of the crop factor that takes place inside the camera, now only has a field of view equal to a 18-36 in the Ninon DSLRs.

1-Advantage. A 200mm becomes a 300mm, only smaller and lighter.
2-Advantage. Your "18mm" now has the depth of field of a 12mm - because it is.

3- Disadvantage for some is they want less depth of field. Personally, I need all I can get. This is critical with longer lenses as DOF becomes a real problem. In landscapes DOF is also very critical. However, when selective focus is needed, it becomes a disadvantage. Some get around this by raising the shutter speed and shooting with a wider f stop.
--
Steve Bingham
http://www.dustylens.com
 
Steve Bingham said:
2-Advantage. Your "18mm" now has the depth of field of a 12mm -
because it is.
Click to expand...
Yes, apparently ... but you must compensate for the smaller pixel size required, if same resolution on FF is wanted - and thos counterweights the bette DOF (I don't know if it is a break even)

Kim
 
in the DX format,

as pixel density increases,
the necessity for higher resolving power of the lens needs to increase as well ?

I know of only a couple of Nikon lenses that approach the resolution of the D200,

and as the mega pixels increase, aren't we going to need sharper lenses if the sensor area is held constant ?
The only other way is to increase the sensor area and approach full frame size,

that is, if we want to use our current arsenal of non-dx lenses in the future and maintain utmost sharpness.

I point this out, because if you ever loupe a high end print, like an Ansel Adams, you see such amazing detail from edge to edge, absolutely stunning the detail that is captured.
 
You need to realize that the focal length of a lens is a physical attribute that cannot be made up to accommodate for field of view. So, 35mm is 35mm regardless whether you use it on film SLR or medium format camera or DX sized camera. Similarly, a DX lens (which mainly incorporates reduced image circle and tele-centric design) is still a lens and if the focal length is written as 35mm, it will be 35mm. How much the field of view is will be dependent on the size of the film or sensor.

--
Speed is significant and interesting but accuracy is downright fascinating
http://www.pbase.com/pradipta
 
Kevin Nguyen said:
I think the only differnces between digital lens vs non digital
would be the ability for you look through the viewfinder and see
exactly what will be send to the sensor vs non digital where what
you see is not exactly what you will get...
Click to expand...
That is completely wrong.

Regardless of whether you use a DX lens or any other lens, the camera viewfinder will only show what will be captured (within the tolerance obviously).

--
Speed is significant and interesting but accuracy is downright fascinating
http://www.pbase.com/pradipta
 
that you really arent getting a 300mm lens from a 200mm lens. what you are getting is a crop and essentially lost information.

to me its like widescreen and full screen with movies. yes, the full screen version fills up a 4:3 TV, but it's doing so at a loss of nearly 1/3 of the actual information.
--

Disagree with me all you like, but remember I have a right to an opinion and a right to state it.
http://www.thekmiecs.com
http://www.adamkmiec.com
 
But no one said you were getting a 300m lens. What is said is that 200mm on a DX body gives you an EQUIVALENT of a 300mm focal length. And if you go out with your buddy, you with your DX body and 200m lens, he with his 35mm SLR and 300mm lens, you both stand in the same place, shoot the same object, and both print 6x4's, you'll see this is true (for field of view and therefore apparent manification).

--
Geoff

WSSA member#68
PBase Supporter

http://www.pbase.com/tuckeruk
 
since FF lenses already exist and we operate in a 35mm world it's the DX lenses that need to change :)

if you have a 200mm lens and you put that lens on a 1.5X crop DSLR and a FF DSLR and shoot from the same exact location, you are in fact missing 50% of the information when shooting with a 1.5X crop DSLR.
--

Disagree with me all you like, but remember I have a right to an opinion and a right to state it.
http://www.thekmiecs.com
http://www.adamkmiec.com
 
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