Now that we have brilliant DX cameras like the D5200 and D7100, am I alone in thinking that some primes to go with them would be a good idea?
Imagine a 300/4 in DX for sports and wildlife. How much smaller, lighter and cheaper could that be than the highly regarded FX model?
Maybe Nikon wouldn't be keen to undercut their FX lenses. But Sigma seem to be on a roll...

I hear what you are saying. But... bear in mind that I am over 70 and weigh in at a measly 135lbs. Every ounce counts!
I'm just interested to know if anyone could calculate the possible saving in size and weight if there were some DX primes available?
I've tried my DX Sig 30/1.4 on my D800 with the 1.2 crop factor. That gives me a 36mm F1.4 (with minimal vignetting). It's a whole lot lighter and cheaper than the Sig FX 35.:smile:

Telephoto lenses can't be made smaller for DX. The limiting factor for telephotos is that the front element has to be at least the focal length divided by the maximum aperture. So for the 300 f/4, the front element has to be at least 75 mm. This is regardless of whether it is designed for a DX or FX sensor. The Nikon 300 f/4 AF-S takes a 77 mm filter, so the front element is probably right around the smallest that it can be. This is why there are no telephoto lenses for DX sensors only.

On the other hand, for wide-angle and 'normal' lenses, there can be a size/weight advantage to designing for DX sensors.

Im not a big prime user. I have never shot FX. But there are 3 primes I really like on DX.
First is the 300 F4. Not light in my book but it never diasappoints. The next one I like a lot is the 40mm 2.8 mico. Its cheap, light, SHARP, & little to no distortion. Lastly I love the results of the 200F4 AIS. SHARP, lightweight, but is manual focus.

Telephoto lenses can't be made smaller for DX. The limiting factor for telephotos is that the front element has to be at least the focal length divided by the maximum aperture. So for the 300 f/4, the front element has to be at least 75 mm. This is regardless of whether it is designed for a DX or FX sensor. The Nikon 300 f/4 AF-S takes a 77 mm filter, so the front element is probably right around the smallest that it can be. This is why there are no telephoto lenses for DX sensors only.

On the other hand, for wide-angle and 'normal' lenses, there can be a size/weight advantage to designing for DX sensors.

Thanks, that answers my query. I had assumed that a DX lens of the same spec would automatically be smaller.
I used to have a 300/4, when I was younger and fitter. A great lens to be sure!

If you want smaller primes the only size advantage you'll find are with mirrorless cameras. You still have the large flange distance with Nikon. So DX lenses aren't that much smaller to their FX equivalent.

Telephoto lenses can't be made smaller for DX. The limiting factor for telephotos is that the front element has to be at least the focal length divided by the maximum aperture. So for the 300 f/4, the front element has to be at least 75 mm. This is regardless of whether it is designed for a DX or FX sensor. The Nikon 300 f/4 AF-S takes a 77 mm filter, so the front element is probably right around the smallest that it can be. This is why there are no telephoto lenses for DX sensors only.

On the other hand, for wide-angle and 'normal' lenses, there can be a size/weight advantage to designing for DX sensors.

Further to this, I'm confused by this comparison:-
55-300mm DX - filter size 58mm.
70-300mm FX - filter size 67mm. Both at f5.6.
It would seem from this that a DX lens can be made smaller? Or have I got it a over t.

If you want smaller primes the only size advantage you'll find are with mirrorless cameras. You still have the large flange distance with Nikon. So DX lenses aren't that much smaller to their FX equivalent.

Glenn, sounds like you and I are in the same boat (and it doesn't draw much water :smile. I am also over 70 and 140 lbs, and I'm always complaining about the size and weight of cameras and lenses. I have a 300/4 but I use it only on a tripod and I don't carry it very far.

Thom Hogan has been chiding Nikon about the lack of DX primes for several years.

With my D7000, I like to use my 40mm f/2.8 Nikkor micro when I'm going to be walking very far. I also get a good bit of use from my 85mm f/3.5 micro.

Point taken. 300/53 = 5.6 (approx).
But 300/67 = 4.5 (approx).
So - if the 70-300 has a 67mm front element, why is it not a F4.5, rather than 5.6?
Is it because it is 4.5 at the short, 70mm end?
I'm not enough of a mathematician to work this out!

In designing a lens, I think that there are multiple factors to take into accound, like optimum aperture for the glass used, vignetting produced (that alone allows the DX lenses to be designed more sloppy... they need only cover about half the frame) and, very important, marketing desires.

Hmmm, I'm 65 and 200 but I took my Mother out for BIF @ Bosque last year (84 and 135)
and she handled the 300 f4 on a BushHawk like it was a piece of toast. There will be NO
"DX" primes over 85mm, so sorry....pointless pursuits. :frown: You need to think WIDER,
the new Sigma 18-35 f1.8A will be a stunner...IF you can handle the 1.8 lbs. :biggrin:

Point taken. 300/53 = 5.6 (approx).
But 300/67 = 4.5 (approx).
So - if the 70-300 has a 67mm front element, why is it not a F4.5, rather than 5.6?
Is it because it is 4.5 at the short, 70mm end?
I'm not enough of a mathematician to work this out!

Don't get too hung up about front element size with respect to focal length and max aperture. There isn't always a direct relation, outside of a minimum required size as was mentioned above.

Glenn, sounds like you and I are in the same boat (and it doesn't draw much water :smile. I am also over 70 and 140 lbs, and I'm always complaining about the size and weight of cameras and lenses. I have a 300/4 but I use it only on a tripod and I don't carry it very far.

Thom Hogan has been chiding Nikon about the lack of DX primes for several years.

With my D7000, I like to use my 40mm f/2.8 Nikkor micro when I'm going to be walking very far. I also get a good bit of use from my 85mm f/3.5 micro.

Hmmm, I'm 65 and 200 but I took my Mother out for BIF @ Bosque last year (84 and 135)
and she handled the 300 f4 on a BushHawk like it was a piece of toast. There will be NO
"DX" primes over 85mm, so sorry....pointless pursuits. :frown: You need to think WIDER,
the new Sigma 18-35 f1.8A will be a stunner...IF you can handle the 1.8 lbs. :biggrin:

In designing a lens, I think that there are multiple factors to take into accound, like optimum aperture for the glass used, vignetting produced (that alone allows the DX lenses to be designed more sloppy... they need only cover about half the frame) and, very important, marketing desires.

Don't get too hung up about front element size with respect to focal length and max aperture. There isn't always a direct relation, outside of a minimum required size as was mentioned above.

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