DX - FX photo explanation of crop zoom
- Thread starter Moab Man
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Here's how I think of it. If you read the detailed EXIF data in a picture on a DX body, you'll see (I'm paraphrasing the titles of the data fields):
Focal length: 50mm
Multiplier: 1.5x
Effective focal length: 75mm
That's saying your lens was set at 50mm; but the DX sensor makes the picture equivalent to what a 75mm lens would have produced on an FX body.
The good news is that lens makers have caught on to this and started producing lenses like the 35mm that, as explained in other posts above, will give a (almost) the same results as a 50mm on an FX body. In general it's not something to worry too much about; if you want the same view as with an FX body, you're going to need a wider lens on a DX body.
(Pretty much every camera's EXIF data I've looked at has this info - Nikon, Canon point and shoots, and even most cell phone cameras.)
Focal length: 50mm
Multiplier: 1.5x
Effective focal length: 75mm
That's saying your lens was set at 50mm; but the DX sensor makes the picture equivalent to what a 75mm lens would have produced on an FX body.
The good news is that lens makers have caught on to this and started producing lenses like the 35mm that, as explained in other posts above, will give a (almost) the same results as a 50mm on an FX body. In general it's not something to worry too much about; if you want the same view as with an FX body, you're going to need a wider lens on a DX body.
(Pretty much every camera's EXIF data I've looked at has this info - Nikon, Canon point and shoots, and even most cell phone cameras.)
That is very poorly worded in your Exif tool.
A lens only has one focal length (OK, one at any one zoom setting).
Your data says Focal Length 105mm. Which is also what the lens surely reports.
What it says is 35mm focal length 157mm can only mean another lens on another camera (of FX format) would use a 157mm lens to see the same view as the 105mm is seen in your camera. It is about the scene your sensor shows. IT DOES NOT SAY YOUR LENS IS EVER 157mm. It says your lens is 105mm.
The ONLY importance of this comparison is to set a standard to compare the expected field of view on various cameras. Many of us have used 35mm film for years (before digital), and many of us know exactly what to expect a 105mm lens will show (in that frame of reference). All these various little digital sensors though, who knows now? So equivalent 35mm focal length is telling us that on this camera, with this cropped sensor, the 105 mm lens will produce a view comparable to 157 mm on 35 mm film.
That tells many of us a lot. It tells newbies nothing.
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You missed the point.
The point it was poorly worded? I thought I nailed it dead on.
Actually this 35mm comparison seems one of the larger advantages of FX bodies now. Sure, they do a LOT MORE DEGREE of wide angle, and high ISO might be a bit better, and the larger frame needs less enlargement, but mostly, now our lenses work like we remembered lenses always worked.
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You did get the point Wayne.
Why is is that this seems so hard to understand by quite a few people. They forget what the physics are. In the expression "cropped sensor", it says it all.
Take a picture with a 50mm lens on a FX camera, print it 8x10, take scissors and cut 1.5 inch around, this will leave you with a ±5x7 picture. This is exactly what happens when you put a 50mm lens on a DX camera.
THE SENSOR IS SMALLER AND IT ONLY SEES THE MIDDLE OF THE IMAGE, THE REST IS CROPPED.
So a 50mm lens will always behave like a 50mm lens, including depth of field, but, if you want to have a certain area included in your picture (let's say a house), you will have to back up with the DX camera to get the same view (this is why it's called Field Of View) as you would have with the FX camera.
Does my explanation help anyone? I sure hope so.
Why is is that this seems so hard to understand by quite a few people. They forget what the physics are. In the expression "cropped sensor", it says it all.
Take a picture with a 50mm lens on a FX camera, print it 8x10, take scissors and cut 1.5 inch around, this will leave you with a ±5x7 picture. This is exactly what happens when you put a 50mm lens on a DX camera.
THE SENSOR IS SMALLER AND IT ONLY SEES THE MIDDLE OF THE IMAGE, THE REST IS CROPPED.
So a 50mm lens will always behave like a 50mm lens, including depth of field, but, if you want to have a certain area included in your picture (let's say a house), you will have to back up with the DX camera to get the same view (this is why it's called Field Of View) as you would have with the FX camera.
Does my explanation help anyone? I sure hope so.
Sorry, but it is you that does not get it yet.
A 14 mm lens has a 14mm field of view, always, no exceptions.
It is just the smaller DX sensor (cropped sensor) that cannot see it all of its wider view.
This is absolutely no fault (or property) of the lens, which is always 14mm.
The effect is simply and only due to the smaller camera sensor, cropping away some of what the lens otherwise sees. Blame the sensor, it is stupid to blame the lens.
I do completely understand it. The point of this thread was to show what the real world outcome is for those not understanding what the final outcome will be due to the crop factor.
For example:
Joe: Wow! That is the most spectacular image of a brick wall. How did you get so much of the wall while standing so close?
Bob: It wasn't hard. I used a 14mm lens. Gave me the width I needed.
Joe now heads to his local camera store and purchases a DX specific 14mm lens for his crop sensor camera since Bob was using a 14mm on his full frame sensor.
The next day...
Joe: I bought a 14mm DX lens for my crop sensor and no matter what I did I couldn't get the full width of the wall without having to back up but ran out of room.
Bob: uhh... Well I shot it on my full frame camera so the area captured is much larger.
For Joe to have duplicated Bob's image he would have needed to have a 9mm lens on his crop sensor camera which would have, due to crop factor, been an approximate equivalent to Bob's 14mm on full frame. And while Joe is strangling Bob for all the money he spent buying the wrong lens, Bob can argue and point out until he is blue in the face (could be from the strangling) about how the lens is still 14mm no matter whether it's on DX or FX and that it's all about the field of view blah blah blah, but none of that matters to Joe if the final product does not look the same and he now has to buy a 9mm lens. If Bob had explained that due to crop factor of Joes camera a 14mm would be the equivalent of a 21mm lens on his crop sensor and that to duplicate the FINAL IMAGE size he would need a 9mm lens Joe would have been much happier and Bob alive. Of course Bob in life, as well as in his strangled death, is still correct that the lens is 14mm, and it's actually all about field of view, but none of that mattered to Joe when the end product wasn't the same.
"Bob's" image at 14mm - FX 14mm lens on full frame.
Here is Joe's image that set him off - DX specific lens at 14mm on a crop sensor.
What I was saying is that if the lens is designated as a DX lens, then why not set it up so that the final image on DX reflects the same as it does on FX. Of course the lens would technically be a 9mm lens, but I'm talking about the final image output since the lens is labelled 14mm and is designated specific or optimized for DX.
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Maybe so, hopefully so, but if so, you might choose your words better.
See? Really crummy wording which only adds to the confusion. The lens never changes its one focal length. That is simply impossible.
It is very much more simple. All that happens is the smaller sensor crops that view, and we see a smaller resulting view.
Smaller than what?
Equivalent or Effective focal length is NEVER about what this DX camera does. It does what it does.
The field of view of a XX mm lens depends on that XX number (which is a fixed magnification, on any lens of same focal length), and depends on the sensor or film size in the camera (which captures some width of view, some portion of that angle). A larger FX sensor covers more width from the angle of view, and a smaller DX sensor simply crops to include less width from the angle of view that the lens projects.
Saying, the FX sensor is larger, which obviously needs more magnification (a 50% longer lens at same distance, or with same lens, stepping up closer to 2/3 the distance) to see only the same narrow view that cropped (smaller) DX sees. How hard is that? If you seek telephoto and apparent magnification (due to the cropping smaller, and then enlarging more), DX is considered a plus. But if you want wide angle, it is tough to get much on DX. Different sensor sizes see different scene views.
The "equivalent" comparison is only about what some other lens on some other (FX) camera does, as a way to compare this current DX field of view result with the expected result on that other camera and other lens.
Nothing changes, not the lens focal length, and not the cropped sensor size. The DX camera does what it does (its small sensor crops the wider view that a FX sensor would cover).
A FX camera does something different, and this crop factor is the way to compare the field of view that the two cameras record with the same lens. If someone is not familiar with what a 150mm lens does on 35mm film format, then it is pointless for them to know that their 105 mm on DX works like 157 mm on FX. At least pointless until the time they contemplate buying a FX camera, then it can be useful to plan their new lenses.
Their 105mm on DX works like 105mm on DX.
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I never said it changed the focal length. I stated right up front to the contrary. The thread ran away with what people thought was being said and not what I said.
From the first post, point #1.
It's not pointless. That is what some on this thread were trying to understand - what the image will be with a certain focal length on DX compared to FX.
Anyway, with all the discussion, I want you and sparky to both know this is not angry arguing. Just intellectual discussion so I hope there are no hard feeling or animosity.
Why, exactly, do you think an FX lens need to have the letters FX emblazoned on it?
Horoscope Fish
Senior Member
Nice dodge...
I never said nor implied they NEED to; I said it would be logical and make the labeling uniform across the product line. Your point, as I see it, is that not having a designation *is* a designation in the, "if it doesn't say X it's Y" sort of way and, further, that things have been done since time immemorial. Which is all fine and good, but doing something one way for a long time does not mean it's been done correctly nor does it bear on the matter at hand because my point is that by clearly labeling FX lenses as FX lenes we have a simple, logical and uniform system of labeling across a product line.
Ever notice how Nikon lables FX camera's with an FX badge... Yeah... Huh... I wonder why that is.
Now answer *my* question.
...
I have.
It appears you cannot accept it, however.
I am, however, done with this thread as it has turned into nothing but trolling.
Horoscope Fish
Senior Member
No, you haven't. You've just repeated the same ideas.
Hmmm... No trolling in this thread. Sorry you feel being held accountable for your responses amounts to trolling.
....
If we actually care:
FX & DX Format Lenses Explained | Learn About FX Lenses & DX Cameras from Nikon
Nikon says "here's why" the lenses:
"DX cameras have the added benefit of being able to use both DX and non-DX NIKKOR lenses—those lenses without the DX designation in their names, i.e. AF-S NIKKOR 14-24mm f/2.8G ED. And here's why.
Each lens is designed to cast an image circle on the camera's sensor. The circle cast by a DX lens is smaller and corresponds to the size of a DX sensor. Non-DX lenses cast a larger image circle corresponding to an FX-format sensor. The DX-format camera can use both types of lenses (DX and FX) since the non-DX lens image circle is larger than needed on a DX-format camera."
Seems to be saying since DX lenses were special and different.. I suspect a historical factor is that the camera lenses Nikon made for decades were 35mm film lenses, without even being aware of the FX designation yet. No reason to mark them FX. Compatible either way, mostly.
But all the digital DSLR cameras they made (until D3 in 2007) were DX, which were not marked DX externally and so maybe FX then did need a distinction. Not exactly fully compatible with DX lenses.
Sorry to say, but Only DX lenses have the DX on them. And it's just to protect someone that has FX to buy a lens that wouldn't cover his sensor. As far as I know, no FX lens has the FX on them.
Browncoat
Senior Member
Coming soon to the "post your flowers pics" thread:
Nikonite 1: Here's my photo of a blue flower!
Nikonite 2: Nice pic! I love indigo colored flowers!
Nikonite 1: It's blue.
Nikonite 2: Indigo.
Nikonite 3: Technically, the flower's hue falls between the Nth parameter of the 117th quadrant of the color spectrum. The correct color is "Cerulean".
Nikonite 1 and 2: STFU NOOB@!@#253dfsga^%$&
Nikonite 1: Here's my photo of a blue flower!
Nikonite 2: Nice pic! I love indigo colored flowers!
Nikonite 1: It's blue.
Nikonite 2: Indigo.
Nikonite 3: Technically, the flower's hue falls between the Nth parameter of the 117th quadrant of the color spectrum. The correct color is "Cerulean".
Nikonite 1 and 2: STFU NOOB@!@#253dfsga^%$&
I ran out of pop corn! 
I think people here knows the difference. The problem is that some are not that good in properly expressing their thoughts technically in writing which leads to an apparent confusion or misunderstanding.
To those who have a FX camera, we all know the difference since it is obvious when we switch between FX, 1.2 and DX mode.
To those who have the D7100, it is similar when switching to the 1.3x crop mode.
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I think people here knows the difference. The problem is that some are not that good in properly expressing their thoughts technically in writing which leads to an apparent confusion or misunderstanding.
To those who have a FX camera, we all know the difference since it is obvious when we switch between FX, 1.2 and DX mode.
To those who have the D7100, it is similar when switching to the 1.3x crop mode.
Sent from my iPhone using Tapatalk
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