sigma 170-500 confusion??

Si Micklewright

Si Micklewright

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Si Micklewright
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Hi all,
Could anyone tell me the difference between the sigma 170-500 apo and the sigma 170-500 apo dg.

Does the dg version give a max focal length of 500mm as its for digital sensors and will the non dg lens have a longer focal length on a cropped sensor like the nikon d70?

Whats the quality difference between these two versions?
Any help greatly appreciated as im looking for a decent telephoto soon,
Thank you.
 
From the sigma webite:

DG (DG Lens)
These are large-aperture lenses with wide angles and short minimum focusing distances. With an abundance of peripheral illumination, they are ideal lenses for Digital SLR Cameras whilst retaining suitability for traditional 35mm SLRs.

DC (DC Lens)
These are special lenses designed so that the image circle matches the smaller size of the image sensor of most digital SLR cameras. Their specialized design gives these lenses the ideal properties for digital cameras, the compact and lightweight construction is an added bonus ! including compact and lightweight construction.
Click to expand...
 
The DG lens doesn't match the sensor size so you wont get the same focal length.
 
Basically Sigma added light absorbing coatings to the inside of their lenses and charge a hefty amount for it, I don't think the non DC would be any worse having had used film lenses on my 350D. Only the DC lenses are for APS-c sensors. The focal length of lenses is always written as a Full Frame measurement, but obviously on an APS-c cam you have to multiply that figure.
 
I have the non DG version and use it on my Canon 30D & 350D. It's the coating that's different, there is more chance of lens flare on the non DG version, otherwise as far as I am aware they are the same. It is Ok when stopped down to around F8, but it isn't the sharpest lens at the long end. It is also heavy and as there is no IS you really need to use it with a tripod. The AF isn't the fastest, especially in low light. For the price it's good, but I would consider other options if finances allow such as the Bigma 50-500.
 
Garry79 said:
The DG lens doesn't match the sensor size so you wont get the same focal length.
Click to expand...

Hey? Can you explain that bit? Surely on a digital SLR you will get the same picture with both. 500mm is 500mm focal length regardless of the sensor size so either 500mm lens will give the same picture on a given sensor. Where they differ is that the DC lens will exhibit vignetting on a full frame camera because it is only designed for use wtih a digital camera.

Andrew
 
When using a lens that has a focal length based on a 35mm format the lens will project an image onto the focal plane of the camera that would cover the size of 35mm film. The sensors in most Digital cameras are smaller than this and so a smaller part of the image is projected onto the sensor. This diagram sort of shows this:

crop_factor.gif


This gives the impression that you are "closer" to the subject. This is known as a crop factor.

On this basis a lens with a focal length of 500mm used on a DSLR would appear to give images more like a 800mm lens.

Check out http://en.wikipedia.org/wiki/Crop_factor#Digital_lenses for a better explanation.
 
informative replies thanks.
The sigma 170-500 apo apears to be a lot cheaper than the DG version, has anybody any experience with the older version (non DG)?
Thanks
 
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