DX lens question

[destrekor]

Okay, so I have a film Nikon SLR (N60), and am kicking around the idea of, sometime in the next year, possibly purchasing a Nikon DSLR. I really hate the whole concept of the DX sensor size, it really bothers me, but full film sensor-size DSLRs are way out of my range in terms of affordability.
Problem being, that means I have to work with getting DX-specific lenses.

But with that in mind, I've started researching quality and cost of various lenses, and I am getting confused.

This was what I was under the impression of:
a regular lens, when used with a DX camera, would be magnified 1.5x, with the sweet spot of the optics bending the light onto the sensor, so soft edges and other optical errors aren't nearly as much of a factor on decent lenses. So a 50mm, regular lens (for 35mm film), would have a 75mm focal length.

However, that made me think, that a lens made and marketed exclusively for DX cameras, with a DX branding on the lens, would have the correct focal length advertised.

I'm looking into lenses, and seeing a 35mm DX lens advertised as matching a 50mm lens for film/FX bodies.
And a 10mm DX fish-eye lens matching a 16mm lens for film/FX bodies.

So which is it? If I buy a 10mm DX lens, am I getting 10mm focal length, or 16mm?

I know it isn't advertised as if it meant 16mm on an FX/film body, because the lens will not focus light onto the furthest sides of the lens, as the optics are not capable of that, so it would not be magnified at all.

 

[jpeyton]

It's pretty simple.

All advertised focal lengths on lenses are without any conversion/crop-factor calculations. It doesn't matter if it's a DX lens or an FX lens.

If you want to calculate the field-of-view with your camera, multiply that advertised focal length by the crop factor. For DX bodies, it's 1.5x. For FX bodies, it's 1.0x.

 

[randomlinh]

why do crop sensors bother you so much?

 

[destrekor]

Originally posted by: jpeyton
It's pretty simple.

All advertised focal lengths on lenses are without any conversion/crop-factor calculations. It doesn't matter if it's a DX lens or an FX lens.

If you want to calculate the field-of-view with your camera, multiply that advertised focal length by the crop factor. For DX bodies, it's 1.5x. For FX bodies, it's 1.0x.

So while that makes sense... I've read numerous times that DX lens won't work for the entire sensor area on FX bodies. Is that correct? Sort of like a circle of the FX sensor will show an image, or if using an full-frame digital body that senses DX frames, will step down to a DX sized area on the sensor, with less pixels. Is that the case?

I guess the marketing just confuses me, because it would make sense if the lenses were marketed accurately for DX bodies if labeled DX, and not working correctly on FX lenses, versus sharing the correct focal length/crop factor for FX bodies, yet manufactured for DX bodies.

 

[destrekor]

Originally posted by: randomlinh
why do crop sensors bother you so much?

crop factors don't necessarily bother me, it's the lesser quality of the DX/APS sensor size.
Less color depth, more noise due to smaller pixel pitch.

I'm a film buff and still say digital cannot compete with the quality of film, but for budget reasons, digital can be a saver, and you get to play around with them on the computer quite easily, versus scanning negatives, and dark rooms are amazing, but cumbersome and cost quite a bit, not to forget the required space - and color is a whole different ball game. Though I would never trade in the ability to play around in a dark room for black and white film versus using digital. Just cannot accurately match B&W film anyhow.

 

[jpeyton]

Originally posted by: destrekor

Originally posted by: jpeyton
It's pretty simple.

All advertised focal lengths on lenses are without any conversion/crop-factor calculations. It doesn't matter if it's a DX lens or an FX lens.

If you want to calculate the field-of-view with your camera, multiply that advertised focal length by the crop factor. For DX bodies, it's 1.5x. For FX bodies, it's 1.0x.

So while that makes sense... I've read numerous times that DX lens won't work for the entire sensor area on FX bodies. Is that correct? Sort of like a circle of the FX sensor will show an image, or if using an full-frame digital body that senses DX frames, will step down to a DX sized area on the sensor, with less pixels. Is that the case?

I guess the marketing just confuses me, because it would make sense if the lenses were marketed accurately for DX bodies if labeled DX, and not working correctly on FX lenses, versus sharing the correct focal length/crop factor for FX bodies, yet manufactured for DX bodies.

While all DX lenses will mount on FX bodies, you're correct that not all will project a full image circle on an FX sensor. You can crop the DX image circle yourself, or have the camera do it for you.

But the current system is IMO the simplest way of doing things. You take the focal length, multiply it by the crop-factor, and you get the field-of-view. If you stick an FX lens on a DX body, you multiply it by 1.5x.

 

[randomlinh]

Originally posted by: destrekor

Originally posted by: randomlinh
why do crop sensors bother you so much?

crop factors don't necessarily bother me, it's the lesser quality of the DX/APS sensor size.
Less color depth, more noise due to smaller pixel pitch

heh, when i said crop sensors, i meant the APS-C realm of sensors =)

are you set on nikon because you have old glass to use? a used 5D is ~1100. otherwise, start savin more money

Originally posted by: destrekor
So while that makes sense... I've read numerous times that DX lens won't work for the entire sensor area on FX bodies. Is that correct? Sort of like a circle of the FX sensor will show an image, or if using an full-frame digital body that senses DX frames, will step down to a DX sized area on the sensor, with less pixels. Is that the case?

pretty much.

 

[destrekor]

Originally posted by: jpeyton

Originally posted by: destrekor

Originally posted by: jpeyton
It's pretty simple.

All advertised focal lengths on lenses are without any conversion/crop-factor calculations. It doesn't matter if it's a DX lens or an FX lens.

If you want to calculate the field-of-view with your camera, multiply that advertised focal length by the crop factor. For DX bodies, it's 1.5x. For FX bodies, it's 1.0x.

So while that makes sense... I've read numerous times that DX lens won't work for the entire sensor area on FX bodies. Is that correct? Sort of like a circle of the FX sensor will show an image, or if using an full-frame digital body that senses DX frames, will step down to a DX sized area on the sensor, with less pixels. Is that the case?

I guess the marketing just confuses me, because it would make sense if the lenses were marketed accurately for DX bodies if labeled DX, and not working correctly on FX lenses, versus sharing the correct focal length/crop factor for FX bodies, yet manufactured for DX bodies.

While all DX lenses will mount on FX bodies, you're correct that not all will project a full image circle on an FX sensor. You can crop the DX image circle yourself, or have the camera do it for you.

But the current system is IMO the simplest way of doing things. You take the focal length, multiply it by the crop-factor, and you get the field-of-view. If you stick an FX lens on a DX body, you multiply it by 1.5x.

and apparently do the same with a DX lens too, eh? Or am I been reading the posts wrong?
a 10mm DX lens will still result in a 16mm focal length on a DX body?

I figure, I'll take my current zoom lens and enjoy the longer magnification, but get a wide angle for DX and not even think of using it on my film SLR or future FX body.

 

[jpeyton]

Okay, time to break out your calculator.

First, look at your lens. It doesn't matter if it's a DX lens or FX lens. Look at the outside of your lens body to find the focal length. That's your first number.

Second, look at your camera body. Is it a DX body? Then your second number is 1.5. If it's an FX body, your second number is 1.

Finally, take your first number and second number and multiply them together. That is your effective field-of-view.

 

[destrekor]

Originally posted by: randomlinh

Originally posted by: destrekor

Originally posted by: randomlinh
why do crop sensors bother you so much?

crop factors don't necessarily bother me, it's the lesser quality of the DX/APS sensor size.
Less color depth, more noise due to smaller pixel pitch

heh, when i said crop sensors, i meant the APS-C realm of sensors =)

are you set on nikon because you have old glass to use? a used 5D is ~1100. otherwise, start savin more money

Originally posted by: destrekor
So while that makes sense... I've read numerous times that DX lens won't work for the entire sensor area on FX bodies. Is that correct? Sort of like a circle of the FX sensor will show an image, or if using an full-frame digital body that senses DX frames, will step down to a DX sized area on the sensor, with less pixels. Is that the case?

pretty much.

I would prefer Nikon, to keep with the F-mount. But I've looked into the Canon's, but wasn't seeing pricing any less than the Nikons. Haven't checked ebay, because really at the time I am definitely not ready to purchase a digital body. Something I'm just thinking about for the future, trying to figure out exactly what route so I am fully prepared whenever I do so. Maybe by then FX bodies will be readily available and cheap. I love amateur photography, just shooting whatever interests me when I have a camera on me, but rarely do I carry my film SLR because of the hassle of film development, not knowing for sure if I got just the right exposure (yes there is bracketing, but moving on ),if I visualized just the right angle or if it didn't translate onto print like I thought it would.

Mostly, it's for the ease of use, which is exactly what I preached against with digital photography. :laugh: I love the work needed for film photography, but that's something you seriously invest money into, and SLRs are never going to do the trick anyhow if going for real art. Medium format and larger is where its at, and I just cannot afford to invest in that right now.

 

[destrekor]

Originally posted by: jpeyton
Okay, time to break out your calculator.

First, look at your lens. It doesn't matter if it's a DX lens or FX lens. Look at the outside of your lens body to find the focal length. That's your first number.

Second, look at your camera body. Is it a DX body? Then your second number is 1.5. If it's an FX body, your second number is 1.

Finally, take your first number and second number and multiply them together. That is your effective field-of-view.

Okay, you confirmed, with repetition, what I was wondering.

So the DX on the lens is just to basically state it'll be worthless on an FX body, correct?

 

[Madwand1]

Originally posted by: destrekor
So the DX on the lens is just to basically state it'll be worthless on an FX body, correct?

Impractical, probably. Worthless, no. Impractical because you wouldn't really want to take a FF camera and put on a lens which throws away more than half the area. Not worthless because given a high-enough resolution FF sensor, the remaining center crop still has enough resolution to be decent.

E.g. D3x: ~24 MP FX, ~11 MP DX.

A 11 MP crop camera with all the other characteristics of a D3x would hardly be "worthless". The fact that you wouldn't want to use it as such is more of a reflection on the value of the FF than the value of the remaining crop.

 

[destrekor]

Originally posted by: Madwand1

Originally posted by: destrekor
So the DX on the lens is just to basically state it'll be worthless on an FX body, correct?

Impractical, probably. Worthless, no. Impractical because you wouldn't really want to take a FF camera and put on a lens which throws away more than half the area. Not worthless because given a high-enough resolution FF sensor, the remaining center crop still has enough resolution to be decent.

E.g. D3x: ~24 MP FX, ~11 MP DX.

A 11 MP crop camera with all the other characteristics of a D3x would hardly be "worthless". The fact that you wouldn't want to use it as such is more of a reflection on the value of the FF than the value of the remaining crop.

That's what I was implying. Owning a full frame body and yet using a lens that is only using an APS size section is a complete waste. Sure, it can be used if necessary, in a pinch if you forgot the correct lenses or whatever, but far from preferable.

edit:
in the end, it wouldn't be too bad, actually somewhat better than using a true DX camera, because you'd get the lower noise and increased color depth that comes with the full frame sensor. Though from what I've seen, everywhere states it's due to larger pixel pitch, yet, when you increase the pixel density with higher megapixel sensors, they must just be investing greater resources into the full frame sensors if they are still maintaining 14bit sensors for FF.
Do any current DX bodies have 14bit depth?

 

[fuzzybabybunny]

Originally posted by: destrekor

Originally posted by: Madwand1

Originally posted by: destrekor
So the DX on the lens is just to basically state it'll be worthless on an FX body, correct?

Impractical, probably. Worthless, no. Impractical because you wouldn't really want to take a FF camera and put on a lens which throws away more than half the area. Not worthless because given a high-enough resolution FF sensor, the remaining center crop still has enough resolution to be decent.

E.g. D3x: ~24 MP FX, ~11 MP DX.

A 11 MP crop camera with all the other characteristics of a D3x would hardly be "worthless". The fact that you wouldn't want to use it as such is more of a reflection on the value of the FF than the value of the remaining crop.

That's what I was implying. Owning a full frame body and yet using a lens that is only using an APS size section is a complete waste. Sure, it can be used if necessary, in a pinch if you forgot the correct lenses or whatever, but far from preferable.

edit:
in the end, it wouldn't be too bad, actually somewhat better than using a true DX camera, because you'd get the lower noise and increased color depth that comes with the full frame sensor. Though from what I've seen, everywhere states it's due to larger pixel pitch, yet, when you increase the pixel density with higher megapixel sensors, they must just be investing greater resources into the full frame sensors if they are still maintaining 14bit sensors for FF.
Do any current DX bodies have 14bit depth?

Currently, yes. D300 offers 14-bit depth.

FYI, if you have a full frame body and use a DX lens on it, the sensor would have to be 18MP if you want the resulting image from the DX lens to be 8MP ( 18 / 1.5^2 ), which is usable. But it would still be far from preferable. The only reasons I see for doing this is if you needed an emergency lens because your primary FF one broke, or you're moving onto FF and you've still got DX lenses, but not enough money to purchase the FF equivalents yet. So you use the DX ones for the time being. All of this is a moot point currently because there are no affordable FF cameras with a resolution over 18MP.

 

[Eltano1]

Interesting thread, but I think everybody missed the point that he has a film camera, with regular lenses (non DX) hence he should be able to use those lenses in a FF Nikon without any issues, correct? OR I'm confuse on this one?
I though that old lenses are usable on either DX or FF, with the advantage/disavantage of having a AF or Manual mode depending on the camera.
Please correct me if I'm wrong.

Regards

Eltano

 

[twistedlogic]

Originally posted by: Eltano1
I though that old lenses are usable on either DX or FF, with the advantage/disavantage of having a AF or Manual mode depending on the camera.
Please correct me if I'm wrong.

Regards

Eltano

You are correct, his old lenses will work on DX or FX. The only problem is some cheaper DX cameras will not meter with AI or AI-S lenses, you need a D200/D300/D700/D3/D2 for metering to work. AF or AF-D lenses should work fine.

To the OP, there is also an adapter that lets you mount Nikon lenses to a Canon body and still retain metering, but you lose AF.

 

[soydios]

Some semantics: focal length is an optical property and does not change with sensor size. A 50mm lens is an optic with a focal length of 50mm irrespective of whatever size sensor you put behind it. Thus it is most accurate and consistent for camera makers to work in focal length instead of angle of view as lenses can be mounted in front of different-sized sensors.

A 50mm lens mounted on a 1.5x crop-factor body provides the same ANGLE OF VIEW as a 75mm lens on a full-frame (FX digital or 35mm film), but it is still an optic with a focal length of 50mm. The angle of view is derived both from the focal length of the optic and the size of the sensor.