Why does nikon....

Started May 28, 2013 | Discussions
davidib17
Regular MemberPosts: 353Gear list
Like?
Why does nikon....
May 28, 2013

Manufacture DX lenses and give them a FX focal length, instead of the equivalent?

 davidib17's gear list:davidib17's gear list
Nikon D5100 Nikon AF-S DX Nikkor 18-55mm f/3.5-5.6G VR Nikon AF-S DX Nikkor 35mm f/1.8G Nikon AF-S DX Nikkor 55-300mm f/4.5-5.6G ED VR Sigma 150-500mm F5-6.3 DG OS HSM +2 more
harpo95993
Forum MemberPosts: 72Gear list
Like?
Re: Why does nikon....
In reply to davidib17, May 28, 2013

davidib17 wrote:

Manufacture DX lenses and give them a FX focal length, instead of the equivalent?

17-55 = 25-82

16-85 = 24-122

35mm = 52mm

55-200 = 82-300

and the list goes on.  Most are pretty close to their FX counter part.

 harpo95993's gear list:harpo95993's gear list
Sony RX100 Konica Minolta Maxxum 7D Nikon D7000 Nikon D7100 Nikon AF-S DX Nikkor 16-85mm f/3.5-5.6G ED VR +18 more
Reply   Reply with quote   Complain
davidib17
Regular MemberPosts: 353Gear list
Like?
Re: Why does nikon....
In reply to harpo95993, May 28, 2013

I do realize that, but it just seems impractical to label something with a length it can never actually be used for.

 davidib17's gear list:davidib17's gear list
Nikon D5100 Nikon AF-S DX Nikkor 18-55mm f/3.5-5.6G VR Nikon AF-S DX Nikkor 35mm f/1.8G Nikon AF-S DX Nikkor 55-300mm f/4.5-5.6G ED VR Sigma 150-500mm F5-6.3 DG OS HSM +2 more
Reply   Reply with quote   Complain
nfpotter
Senior MemberPosts: 4,072
Like?
Re: Why does nikon....
In reply to davidib17, May 28, 2013

davidib17 wrote:

I do realize that, but it just seems impractical to label something with a length it can never actually be used for.

Not really.  Focal length is focal length, and many can be used on both (or more) formats.  Angle of view is what changes, thus the labeling.

Reply   Reply with quote   Complain
davidib17
Regular MemberPosts: 353Gear list
Like?
Re: Why does nikon....
In reply to nfpotter, May 28, 2013

Right. But it the 35mm DX prime can never actually be a 35mm lens. It makes no sense to even bother labeling it with something that has nothing to do with it in actuallity.

 davidib17's gear list:davidib17's gear list
Nikon D5100 Nikon AF-S DX Nikkor 18-55mm f/3.5-5.6G VR Nikon AF-S DX Nikkor 35mm f/1.8G Nikon AF-S DX Nikkor 55-300mm f/4.5-5.6G ED VR Sigma 150-500mm F5-6.3 DG OS HSM +2 more
Reply   Reply with quote   Complain
sshoihet
Senior MemberPosts: 2,223Gear list
Like?
Re: Why does nikon....
In reply to davidib17, May 28, 2013

davidib17 wrote:

Right. But it the 35mm DX prime can never actually be a 35mm lens. It makes no sense to even bother labeling it with something that has nothing to do with it in actuallity.

The 35mm DX lens is ALWAYS 35mm, the same as a 35mm FX lens because the length of the lens doesn't change; only the portion of the images that the sensor sees changes.  People would be even more confused when comparing a 50mm FX lens to a 50mm DX lens because the labelled length would be different depending on what sensor it was made for.

With your proposed scheme, how many people would realize that a 50mm FX, 35mm DX and 18mm CX lens were all the same real focal length and that the 18mm CX lens actually gave you the same FOV of a 50mm FX lens when used on the same camera?

This is not new, we didn't change how we labelled 35mm lenses vs medium and large format lenses.  We can't just arbitrarily choose a sensor size and decide to label all the lenses based on that.

 sshoihet's gear list:sshoihet's gear list
Canon PowerShot S95 Nikon D7000 Canon EOS M Nikon D600 Nikon D7100 +14 more
Reply   Reply with quote   Complain
Mako2011
Mako2011 MOD
Forum ProPosts: 15,038
Like?
no such thing
In reply to davidib17, May 28, 2013

davidib17 wrote:

Manufacture DX lenses and give them a FX focal length, instead of the equivalent?

Because as sshoihet points out...the DX focal length of the 35mm f1.8DX lens is 35mm and not 50mm. There is no such thing as a DX equivalent focal length...there is a such thing though as a equivalent FOV.
-- hide signature --

My opinions are my own and not those of DPR or its administration. They carry no 'special' value (except to me and Lacie of course)

Reply   Reply with quote   Complain
sshoihet
Senior MemberPosts: 2,223Gear list
Like?
Re: no such thing
In reply to Mako2011, May 28, 2013

Mako2011 wrote:

davidib17 wrote:

Manufacture DX lenses and give them a FX focal length, instead of the equivalent?

Because as sshoihet points out...the DX focal length of the 35mm f1.8DX lens is 35mm and not 50mm. There is no such thing as a DX equivalent focal length...there is a such thing though as a equivalent FOV.

What about when you shoot a DX lens on an FX camera, what happens then when you switch it to DX mode?  As you noted, only the AOV changes

Add to that too the fact that many DX lenses will work quite well on an FX sensor and cover the entire frame with little to no vignetting depending on the focal length and or aperture. eg the Sigma 8-16mm works quite well in FX mode at 15/16mm and is still quite good at 14mm.

http://www.dpreview.com/forums/thread/3206935?page=1

 sshoihet's gear list:sshoihet's gear list
Canon PowerShot S95 Nikon D7000 Canon EOS M Nikon D600 Nikon D7100 +14 more
Reply   Reply with quote   Complain
Terry Vickers
Regular MemberPosts: 332Gear list
Like?
Re: no such thing
In reply to sshoihet, May 28, 2013

Focal length in photography is the distance of the rear nodal point of the lens to the image plane.

The formula for FOV = 2 arctan (x / (2 f) where x is the diagonal size of the sensor.

Obviously by changing the x above it will change the FOV regardless of the focal length.

FOV or AOV would probably be a more accurate way of naming lenses in terms of their "zoominess" but it's one of those conventions that has stuck. So we have to use the crop factors to get traditional 35mm FOV equivalents. While a bit of a confusing I think it would be more confusing to call something that it isn't ie. calling a 35mm focal length 50mm when it is in fact 35mm.

The use of equivalents is mainly there to have a commonly understood reference. More convention than anything else.

 Terry Vickers's gear list:Terry Vickers's gear list
Nikon D3100 Nikon D7000 Nikon D5200 Nikon AF-S DX Nikkor 55-200mm f/4-5.6G VR Nikon AF-S DX Nikkor 18-55mm f/3.5-5.6G VR +7 more
Reply   Reply with quote   Complain
stevehughes
Regular MemberPosts: 404Gear list
Like?
Re: no such thing
In reply to Terry Vickers, May 28, 2013

My Dad, an experienced film photographer for decades, still wrestles with this on his D40.  When I tell I just got an 85mm lens he replies with "is that actually 85, or is it 125?"

The fact is that it is an 85mm lens regardless of whether it is mounted on a DX camera or an FX camera.  The focal length is a physical property of the lens.

What I have suggested to Dad is that he just needs to re-learn his concept of what 'normal' etc means when applied to lenses on DX

On film / FX, 50 is normal, 35 semi-wide, 28 wide and 21 ultra-wide

On DX, 35 is normal, 24 semi-wide, 18 wide and 14 ultra-wide.

-- hide signature --

Best regards,
Steve

 stevehughes's gear list:stevehughes's gear list
Nikon D7100 Nikon AF-S DX Nikkor 16-85mm f/3.5-5.6G ED VR Nikon AF-S DX Nikkor 35mm f/1.8G Nikon AF-S DX Nikkor 10-24mm f/3-5-4.5G ED Nikon AF-S Nikkor 85mm f/1.8G +3 more
Reply   Reply with quote   Complain
Sunshine_boy
Veteran MemberPosts: 4,497Gear list
Like?
Currency equivalent!...
In reply to davidib17, May 28, 2013

davidib17 wrote:

Manufacture DX lenses and give them a FX focal length, instead of the equivalent?

That's because the FX value is a universal constant regardless of the camera it is mounted on, as the other posters pointed out. All you need to know is the 'crop factor' of your camera/sensor and multiply it by the indicated FL. Crop factors vary. Nikon's DX factor is 1.5, Canon's is 1.6 etc. So, a 200mm lens would be 200mm on any FF cam, 300mm on a Nikon DX and 320mm on a Canon DX.

Look at it in the same way as specifying a 'value' of a house expressing it in US dollars without having to bother expressing it in half a dozen other major currencies... 

-- hide signature --

Best Regards
Sunshine
Visit my website for lots of pics and fun...
www.sunshine-web.com
ps If you see someone without a smile on, give him one of yours...

 Sunshine_boy's gear list:Sunshine_boy's gear list
Fujifilm FinePix F31fd Fujifilm FinePix S6000fd Olympus C-4000 Zoom Nikon Coolpix P7100 Nikon D60
Reply   Reply with quote   Complain
sshoihet
Senior MemberPosts: 2,223Gear list
Like?
Re: no such thing
In reply to stevehughes, May 28, 2013

stevehughes wrote:

My Dad, an experienced film photographer for decades, still wrestles with this on his D40.  When I tell I just got an 85mm lens he replies with "is that actually 85, or is it 125?"

Then he should have been familiar with some of the popular medium formats like 645, 6x6 and 6x7 where the "normal" lenses were approximately 75mm, 80mm and 90mm respectively.  On 8x10, ~300mm is normal.

We have 2 main sensor sizes now, things were WAY more confusing back in the days of film

 sshoihet's gear list:sshoihet's gear list
Canon PowerShot S95 Nikon D7000 Canon EOS M Nikon D600 Nikon D7100 +14 more
Reply   Reply with quote   Complain
coudet
Veteran MemberPosts: 3,667
Like?
Re: Why does nikon....
In reply to davidib17, May 28, 2013

davidib17 wrote:

I do realize that, but it just seems impractical to label something with a length it can never actually be used for.

It would be even more impractical and wrong to label a lens something that's not. Would you label CX lenses that way too? How about medium format or large format? Should we rename those 360mm lenses for large format too and give them FF equivalent local length?

If it's a 35mm lens, you label it as 35mm and that's the end of it. And besides, what do you mean it can't be used on FF? Shave that 10.5mm and stick on a D800.

Reply   Reply with quote   Complain
lorenzo de medici
Regular MemberPosts: 171Gear list
Like?
Re: Why does nikon....
In reply to davidib17, May 28, 2013

davidib17 wrote:

I do realize that, but it just seems impractical to label something with a length it can never actually be used for.

You can use the lens on a FX body with the DX crop enabled on the sensor.  Like everybody else said, the lens focal length is what it is.

Reply   Reply with quote   Complain
IanYorke
Regular MemberPosts: 102Gear list
Like?
Re: Why does nikon....
In reply to lorenzo de medici, May 28, 2013

lorenzo de medici wrote:

davidib17 wrote:

I do realize that, but it just seems impractical to label something with a length it can never actually be used for.

You can use the lens on a FX body with the DX crop enabled on the sensor.  Like everybody else said, the lens focal length is what it is.

Agreed, focal length is focal length.

Reply   Reply with quote   Complain
blue_cheese
Senior MemberPosts: 1,400
Like?
Re: Currency equivalent!...
In reply to Sunshine_boy, May 28, 2013

Sunshine_boy wrote:

That's because the FX value is a universal constant regardless of the camera it is mounted on,

Really now? Im curious how a 35mm format lens would fit on a medium format camera, I don't see any medum format shooters grandstanding that their sensor should be the be baseline reference for focal length to FOV relationship.

as the other posters pointed out. All you need to know is the 'crop factor' of your camera/sensor and multiply it by the indicated FL. Crop factors vary. Nikon's DX factor is 1.5, Canon's is 1.6 etc. So, a 200mm lens would be 200mm on any FF cam, 300mm on a Nikon DX and 320mm on a Canon DX.

No as others pointed out, the focal length is an attribute of the lens and does not change based on the camera. What changes is the FOV and possibly the amount of vignetting of the image cirlce

Look at it in the same way as specifying a 'value' of a house expressing it in US dollars without having to bother expressing it in half a dozen other major currencies... 

And this is why Canadians have bought up half of Florida

Reply   Reply with quote   Complain
davidib17
Regular MemberPosts: 353Gear list
Like?
Re: Currency equivalent!...
In reply to blue_cheese, May 28, 2013

I wasn't looking for you guys to explain the crop factor to me. I know what that is and I know that full frame is the universal way a lenses focal length is described.

I just thought it wasn't a good idea to label a product with a completely false specification that the product itself can never actually be used for.

 davidib17's gear list:davidib17's gear list
Nikon D5100 Nikon AF-S DX Nikkor 18-55mm f/3.5-5.6G VR Nikon AF-S DX Nikkor 35mm f/1.8G Nikon AF-S DX Nikkor 55-300mm f/4.5-5.6G ED VR Sigma 150-500mm F5-6.3 DG OS HSM +2 more
Reply   Reply with quote   Complain
Mako2011
Mako2011 MOD
Forum ProPosts: 15,038
Like?
not false
In reply to davidib17, May 28, 2013

davidib17 wrote:

I just thought it wasn't a good idea to label a product with a completely false specification that the product itself can never actually be used for.

Problem is...no product is being labeled falsely. Your suggestion that it is indicates you do not understand the meaning of the labeling, so folks tried to help in that regard and accurately answer the question you posed. For example. Every DX lens can be used exactly for the focal length it is labeled on DX and many FX cameras. The manual that goes with the lens explains the output results.  Do you have an example of "the product itself" unable to meet the labeling spec?

-- hide signature --

My opinions are my own and not those of DPR or its administration. They carry no 'special' value (except to me and Lacie of course)

Reply   Reply with quote   Complain
davidib17
Regular MemberPosts: 353Gear list
Like?
Re: not false
In reply to Mako2011, May 28, 2013

Mako2011 wrote:

For example. Every DX lens can be used exactly for the focal length it is labeled on DX and many FX cameras. The manual that goes with the lens explains the output results.

A DX 35mm lens can not, and will not ever be able to take a picture at the same zoom length as a FX lens on a full frame camera set at 35mm, no?

 davidib17's gear list:davidib17's gear list
Nikon D5100 Nikon AF-S DX Nikkor 18-55mm f/3.5-5.6G VR Nikon AF-S DX Nikkor 35mm f/1.8G Nikon AF-S DX Nikkor 55-300mm f/4.5-5.6G ED VR Sigma 150-500mm F5-6.3 DG OS HSM +2 more
Reply   Reply with quote   Complain
blue_cheese
Senior MemberPosts: 1,400
Like?
apples to apples
In reply to davidib17, May 28, 2013

davidib17 wrote:

Mako2011 wrote:

For example. Every DX lens can be used exactly for the focal length it is labeled on DX and many FX cameras. The manual that goes with the lens explains the output results.

A DX 35mm lens can not, and will not ever be able to take a picture at the same zoom length as a FX lens on a full frame camera set at 35mm, no?

Sure it will, you take a 35mm lens... put in on FX (like a D800 for purposes of MP @36MP), and crop out the outer 33% all around and voila you have a 16MP D7000 image taken with the exact same 35mm.

Nothing to do with lens, not that the lens did not change in the above scenario

Reply   Reply with quote   Complain
Keyboard shortcuts:
FForum MMy threads