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Archive 2016 · basic question regarding DX vs FX

  
 
Keiththom
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p.1 #1 · p.1 #1 · basic question regarding DX vs FX


As many discussions as I've read regarding Crop vs FF cameras, I'm still fuzzy on this point:

If I take my D500 (crop camera) and shoot a shot with my Nikon 12-24 lens at 12mm,

Then take my D810 (full frame) camera and make the same shot with a Nikon 14-24 at 14mm,

Which shot will result in the widest shot?

What's confusing me is that I keep hearing, "you lose some of the wide angle because of the crop camera."

And also " A 12 mm is still a 12 mm, no matter which camera it's on."

(I'd do the test myself, except I haven't ordered the 14-24 yet)

Can anyone "un-confuse" me?





Aug 05, 2016 at 02:16 PM
drtaylor23
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p.1 #2 · p.1 #2 · basic question regarding DX vs FX


We're really just talking about what slice of the world gets jammed into the image. Since we're in the landscape forum let's take a horizontal view of the world. Out of a possible 360 degrees how much do we get in?

https://www.nikonians.org/reviews/fov-tables

12mm DX = 88.5
14mm FX = 104.3

FX 14mm is wider. 12mm DX gives an equivalent field of view for ~18mm on FX. 1.5x crop factor turns up in the math!

That help?



Aug 05, 2016 at 02:49 PM
Keiththom
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p.1 #3 · p.1 #3 · basic question regarding DX vs FX


drtaylor23 wrote:
We're really just talking about what slice of the world gets jammed into the image. Since we're in the landscape forum let's take a horizontal view of the world. Out of a possible 360 degrees how much do we get in?

https://www.nikonians.org/reviews/fov-tables

12mm DX = 88.5
14mm FX = 104.3

FX 14mm is wider. 12mm DX gives an equivalent field of view for ~18mm on FX. 1.5x crop factor turns up in the math!

That help?


It does.
Thanks



Aug 05, 2016 at 03:34 PM
mawz
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p.1 #4 · p.1 #4 · basic question regarding DX vs FX


Take your D810 and take a shot in FX mode at a given focal length with a given lens.
Then put your D810 in DX crop mode and take a shot with the same lens and same focal length.

That will illustrate the difference between FX and DX very well. The D810 in DX crop mode is identical to shooting a DX camera in terms of field of view and depth of field.



Aug 12, 2016 at 12:34 PM
runamuck
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p.1 #5 · p.1 #5 · basic question regarding DX vs FX


Tamron-usa.com has an interactive app on their website. Go to Tamron Lens Line>Find the Right Lens. Use the blue slider to find the focal length and then click either film or digital. (Digital shows the DX (APS-C) field of view and the film icon shows the FX or full frame field of view.
http://www.tamron-usa.com/lenses/learning_center/tools/focal-length-comparison.php



Aug 12, 2016 at 01:23 PM
Lauchlan Toal
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p.1 #6 · p.1 #6 · basic question regarding DX vs FX


The easiest way to think of it is in terms of equivalent focal length - the 12mm on a DX body is equivalent to a 18mm on an FX body, so 14mm on FX is wider. This is because the FX sensor is 1.5 times bigger than the DX sensor, so lenses on DX appear to be 1.5 times longer than their listed focal length, relative to the same focal length on FX.

EDIT: The 12mm is 12mm is true, but deceiving. Yes, a 12mm lens is always a 12mm lens. This is the actual, physical design of the lens. But when we talk about lenses we don't care about the lens design, we care about the field of view that we get - what actually fits in our picture. Most photographers use the FX format as the baseline, and use it to compare lens equivalencies. So DX has a smaller sensor, and we say it has a 1.5x crop relative to FX. Medium format cameras have larger sensors than FX, so we say they have a ~0.62x crop. So that 12mm lens on a crop sensor camera gives you an 18mm field of view on a DX camera and a 7.5mm field of view on a medium format camera, all relative to the FX camera. You could just as easily relate it to a DX camera instead - say that 12mm lens is 12mm equivalent on DX and 8mm equivalent on FX, but we've all pretty much agreed to use FX as the ruler. So crop factor is just a way to define the field of view relative to different formats, even though the lens itself is unchanged. It's just that the 12mm lens on DX looks like a 18mm lens on FX, and so we say it has an 18mm equivalent focal length so everyone knows what kind of field of view is provided.



Aug 12, 2016 at 02:47 PM
Andrew Pece Photography
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p.1 #7 · p.1 #7 · basic question regarding DX vs FX


Relative sizes of objects are going to stay the same at a given focal length, no matter if it's dx or fx. That's the important part about it all I think. So, if you wanted to make an ocean view look more or less natural as the eye sees it, you'd use a 50mm lens on either dx or fx, it's just that in fx you'd get to see more of the view on each side of the frame because the sensor is bigger. Same exact shot, you're just getting more of the view on fx. I think the "equivalent focal lengths" terminology is a bit deceiving because going from say 18mm on an fx to 12mm on a dx, you're composition is "the same", but the relative sizes of everything in the frame have now changed.


Aug 13, 2016 at 08:15 AM
Lauchlan Toal
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p.1 #8 · p.1 #8 · basic question regarding DX vs FX


Andrew Pece Photography wrote:
Relative sizes of objects are going to stay the same at a given focal length, no matter if it's dx or fx. That's the important part about it all I think. So, if you wanted to make an ocean view look more or less natural as the eye sees it, you'd use a 50mm lens on either dx or fx, it's just that in fx you'd get to see more of the view on each side of the frame because the sensor is bigger. Same exact shot, you're just getting more of the view on fx. I think
...Show more

It's actually the distance to the sensor that affects perspective/relative sizes, not the focal length itself. So while you're right in saying that the relative sizes are the same for the 12mm lens on both FX and DX it's just that DX is cropped in, if you put an 18mm lens on the FX camera and kept it in the same location it would give the exact same image as the 12mm lens on DX - same relative sizes, perspective, and everything.



Aug 13, 2016 at 08:40 AM
trenchmonkey
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p.1 #9 · p.1 #9 · basic question regarding DX vs FX


everything...except DOF?!


Aug 13, 2016 at 08:47 AM
Lauchlan Toal
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p.1 #10 · p.1 #10 · basic question regarding DX vs FX


trenchmonkey wrote:
everything...except DOF?!


Weeeell... If it's an 18mm f2.8 and a 12mm f2.8 then yeah, the 18mm will have less DoF. But if you account for the crop factor with the aperture, and have a 12mm f2.8 against an 18mm f4.2, then they'll have the same DoF. But since full frame and DX lenses generally have the same apertures (barring Sigma's line-up of f1.8 zooms), practically the FX would have thinner DoF.

Man, photography's getting too complicated...



Aug 13, 2016 at 09:12 AM
trenchmonkey
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p.1 #11 · p.1 #11 · basic question regarding DX vs FX





Aug 13, 2016 at 09:26 AM
Two23
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p.1 #12 · p.1 #12 · basic question regarding DX vs FX


Keiththom wrote:
Which shot will result in the widest shot?

What's confusing me is that I keep hearing, "you lose some of the wide angle because of the crop camera."

And also " A 12 mm is still a 12 mm, no matter which camera it's on."

(I'd do the test myself, except I haven't ordered the 14-24 yet)





Assume you are projecting a photo onto a screen with a projector. The image is 4x4 feet. You then switch to a screen that is 3x3 feet square. Same distance. Same lens. The square feet of the image is now smaller; you see less of it. The lens hasn't changed. The distance to the screen hasn't changed. The surface area of the screen is smaller.


The best ultrawide DX lens I'm aware of is the Tokina 11-16mm f2.8. There is also a Sigma 8-16mm. I'd get that rather than the 14=24mm, The 14mm will be like using 21mm on an FX. (Smaller screen, less surface areas.)


Kent in SD




Aug 13, 2016 at 11:35 AM
Two23
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p.1 #13 · p.1 #13 · basic question regarding DX vs FX


Lauchlan Toal wrote:
Weeeell... If it's an 18mm f2.8 and a 12mm f2.8 then yeah, the 18mm will have less DoF. But if you account for the crop factor with the aperture, and have a 12mm f2.8 against an 18mm f4.2, then they'll have the same DoF. But since full frame and DX lenses generally have the same apertures (barring Sigma's line-up of f1.8 zooms), practically the FX would have thinner DoF.

Man, photography's getting too complicated...



Yes, that is correct. DoF is determined by two things: image size and aperture. The bigger the sensor or film, the less DoF. There is a tremendous loss of DoF between 4x5 and 8x10 view cameras, which is why LF camera lenses can often stop down to f128. A DX camera has about one more stop worth of DoF than an FX.


Kent in SD




Aug 13, 2016 at 11:38 AM
Two23
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p.1 #14 · p.1 #14 · basic question regarding DX vs FX


Lauchlan Toal wrote:
The easiest way to think of it is in terms of equivalent focal length .



Well, there's an even easier way. I regularly shoot a Nikon D3300 DX, D800E & Nikon F3T 35mm, Bessa 6x9cm, Chamonix 045n 4x5, and Gundlach Korona 5x7 I don't think of lenses in terms of length or "mm". For each format I have three lenses. They are based on doubling focal length. Roughly, in FX/35mm terms, it's 24/50/100mm. The actual numbers are different for each format, of course (for 4x5 my lenses are 90/150/300mm) Normal lens on DX is about 35mm, on FX 50mm, on 6x6 it's 80mm, on 6x9 it's 105mm, on 4x5 it's 150mm, on 5x7 it's 200mm......... The way I think of them is I have a wide lens, a normal lens, and a telephoto. Since I'm more than just an FX/35mm shooter, it makes little sense for me to get hung up on millimeters, but rather think of lenses in terms of how they perform.



Kent i SD




Aug 13, 2016 at 11:49 AM
Keiththom
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p.1 #15 · p.1 #15 · basic question regarding DX vs FX


OK guys. I got it. Thanks!



Aug 13, 2016 at 07:41 PM
garyvot
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p.1 #16 · p.1 #16 · basic question regarding DX vs FX


It's more confusing than it really needs to be. Just think of the DX sensor as representing a crop of the FX sensor and you'll have the basic idea.

While a 12mm lens is indeed a 12mm lens, it's field of view changes when you crop in. Due to the crop caused by the smaller sensor, you now have the equivalent field of view of an 18mm lens (on full frame).

However, the depth of field of the 12mm lens is unchanged, and is greater than the 18mm lens. That's why FX sensors provide greater depth of focus control and subject isolation when shooting from the same distance and aperture using lenses with equivalent fields of view.



Aug 14, 2016 at 09:20 AM
trenchmonkey
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p.1 #17 · p.1 #17 · basic question regarding DX vs FX


That's why FX sensors provide greater depth of focus control and subject isolation when shooting from the same distance and aperture using lenses with equivalent fields of view.
Nicely put. So, if you can't see the difference...save yourself some money and shoot DX



Aug 14, 2016 at 09:40 AM
SoundHound
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p.1 #18 · p.1 #18 · basic question regarding DX vs FX


The DX frame area is approx. 40% of the FF area. So the DX format is inferior to FX for the lowest light Highest ISO by more than a full stop (everything else being equal).

DX works well (best?) when you need the longest FL. Because of the 1.5X "Crop a Factor" it is harder to find Wide Angle lenses for DX.

FF lenses are bigger/heavier and often much more expensive than DX lenses So the decision to buy DX or FX should be made with consideration of the system cost (lenses and accessories included).



Aug 14, 2016 at 09:54 AM
nolaguy
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p.1 #19 · p.1 #19 · basic question regarding DX vs FX


garyvot wrote:
Just think of the DX sensor as representing a crop of the FX sensor and you'll have the basic idea.


This. They should call DX a crop sensor.



Aug 14, 2016 at 09:54 AM
morrismike
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p.1 #20 · p.1 #20 · basic question regarding DX vs FX


SoundHound wrote:
The DX frame area is approx. 40% of the FF area. So the DX format is inferior to FX for the lowest light Highest ISO by more than a full stop (everything else being equal).

DX works well (best?) when you need the longest FL. Because of the 1.5X "Crop a Factor" it is harder to find Wide Angle lenses for DX.

FF lenses are bigger/heavier and often much more expensive than DX lenses So the decision to buy DX or FX should be made with consideration of the system cost (lenses and accessories included).


What comes out of the back of the lens is the same regardless of the size of the sensor (sensor sites read intensity of light). The DX sensor actually gets the brightest (center of lens) part of what comes out of the lens. The DX has more pixel pitch making it the natural choice for most of us. I'm thinking (koolaid aside) most folks wouldn't have any issues with high iso shooting D500 vs. D750 and they'd like the D500 more for its AF. Saying the DX format is inferior doesn't seem quite right.



Aug 14, 2016 at 11:49 AM
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