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Sensor size question
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Jan 12, 2021 16:50:36   #
John7199 Loc: Eastern Mass.
 
OK Beating a dead horse, but I'm an old codger.

Proud owner of a Nikon D5600, which I just heard Nikon is discontinuing.
When buying lens I know the certain lens will not operate at the stated focal length as others. Because of sensor size a 150mm will operate as a ??mm.

Please explain in non technical parlance. Also is there a formula to use?

This time I'll keep the answer. Thanks John

Jan 12, 2021 16:55:12   #
CHG_CANON Loc: the Windy City
 
The Nikon crop factor is 1.5x. The focal length of the lens is the focal length of the lens, expressed in millimeters, regardless of the sensor size. The crop factor impacts the field of view where a 100mm lens, for example, will result in the equivalent field of view of a 150mm lens on a full-frame camera. The 100mm focal-length image is cropped by the camera sensor, the lens doesn't change.

Digital camera models are manufactured for about 2-years, in this fast-paced industry. Being discontinued has no impact on your camera. Over time, say another 2- to 5-years after the model is no longer being made / sold, support will end such that Nikon (Canon, etc) will not maintain model-specific parts for repair work. But, as a modern industry-standard 24MP digital camera, you easily can expect 10+ years of usage from this advanced DSLR model.

Jan 12, 2021 16:56:50   #
Thomas902 Loc: Washington DC
 
John; you're dealing with "Field of View" here...
A lens' Focal Length never changes... however for your epic D5600 simply multiple the optics Focal Length by 1.5 to get what is known as "apparent Field of View"

Worry more about composition maybe...
The good news is what you see through the viewfinder is what you'll get :)
Hope this helps John... Please stay safe...

And yes Zoom optics change their Focal Lengths albeit the DX format crops it to a 1.5 "Field of View"
Best to obtain DX optics for your lovely camera

 
 
Jan 12, 2021 16:57:07   #
bleirer
 
You will find a little table in this article https://photographylife.com/what-is-crop-factor

Jan 12, 2021 17:16:52   #
John7199 Loc: Eastern Mass.
 
Great article. I think I get it now. Thanks for not being short with the Codger.

Jan 12, 2021 17:24:37   #
Photocraig
 
CHG_CANON wrote:
The Nikon crop factor is 1.5x. The focal length of the lens is the focal length of the lens, expressed in millimeters, regardless of the sensor size. The crop factor impacts the field of view where a 100mm lens, for example, will result in the equivalent field of view of a 150mm lens on a full-frame camera. The 100mm focal-length image is cropped by the camera sensor, the lens doesn't change.

Digital camera models are manufactured for about 2-years, in this fast-paced industry. Being discontinued has no impact on your camera. Over time, say another 2- to 5-years after the model is no longer being made / sold, support will end such that Nikon (Canon, etc) will not maintain model-specific parts for repair work. But, as a modern industry-standard 24MP digital camera, you easily can expect 10+ years of usage from this advanced DSLR model.
The Nikon crop factor is 1.5x. The focal length of... (show quote)


John, think of it this way, some old Codgers are still laying down rubber patches in their 494 Chevelle SS's. I have a friend with a '40 Ford Coupe with a HEAVILY modified Hemi. I can hear him a mile away. Out of manufacture for many years, but still doing the trick!

That 5600 should shoot straight for a loooong time.

Another way to describe lenses and formats is that lenses project a circular image. Our sensors (like film and paper) are in square or rectangular formats. The lens projects according to the focal length of the lens--by design. The rectangle image size is determined by the sensor size.

The whole 35mm equivalent lingo was born in the early days when sensors were relegated to being smaller, because of manufacturing cost, complexity and yields of semiconductor manufacturing of larger sensors. The MARKET for these new and very expensive Digital Cameras, their actual form factor was the 35mm SLR photographer. Being one, I had a field of view "Picture in my head" of the various prime lens focal lengths, maybe you do, too. So I knew pretty much what a 100mm lens would deliver on a 35mm film frame. That's why the "equivalent" lingo took hold. As we die off, maybe this misleading and confusing lingo will go away. Hope so.
C

Jan 12, 2021 17:29:51   #
CO
 
Nikon has a lens simulator online:
https://imaging.nikon.com/lineup/lens/simulator/

I selected a full frame 50mm lens, and used the simulator to see the view on a full frame D750 and cropped sensor D5000 series.
FX 50mm lens on FX body
FX 50mm lens on FX body...
(Download)
FX 50mm lens on DX body
FX 50mm lens on DX body...
(Download)

 
 
Jan 12, 2021 17:51:03   #
quixdraw Loc: American Free States -- Montana
 
The Nikon Simulator is a great and useful tool that you don't hear much about. An excellent resource.

Jan 12, 2021 21:46:29   #
User ID
 
quixdraw wrote:
The Nikon Simulator is a great and useful tool that you don't hear much about. An excellent resource.


A simple approach is to ignore all references to “crop factor” and never think in that mode.

Just accept the FL marked on the lens. It represents some specific view. If you choose to know a little something about the numeric markings, just know that “normal” is 30 to 35mm for any APSC camera. Knowing that much you can wing it about any longer or shorter FLs.

——————————————————

——————————————————


Consider how the “crop factor” arose. Everyone who used 24x36 film or sensors already knew what the view looks like for any FL. It was almost instinct. It was not intellect or formula.
“Crop factor” was a formulaic crutch for those users to help them adjust to early DSLRs which were NOT the familiar 24x36 format.

The crop factor is obsolete. Today the smaller format is ubiquitous. The time for numeric translation is past. Just get to know the view based on marked FL. Be just like the millions of 24x36 users. You are one of the millions of 18x36 users. What worked for decades of 24x36 users will work for you.

Did 24x36 users burden themselves by thinking that they were operating with a 1.8x crop factor ? Never crossed their minds ... but technically that was the conversion factor from the rollfilm that was ubiquitous before 24x36 (35mm film) displaced rollfilm. No one thought about any “crop factor”, so why should you ? What’s it get you ?

For any camera, FL indicates a view, arithmetic does not.

Jan 13, 2021 03:27:07   #
R.G. Loc: Scotland
 
Starting with a DX focal length, the full frame (FF) equivalent is 1.5 times that. In other words a 100mm DX lens gives the same field of view as a 150mm FF lens.

Starting with a FF lens, the DX equivalent is 1/1.5 times that - which isn't a simple calculation but you can make it simpler. Multiplying by 1.5 (DX > FF) is the same as multiplying by 3/2, so going from FF to DX (the inverse of going from DX to FF) is the same as multiplying by 2/3 (the inverse of 3/2).

That's easy if the figure is easily divisible by 3 - for example 24mm FF is the equivalent of 16mm DX (1/3 of 24 is 8, so 2/3 is twice that, giving 16).

If the number isn't easily divisible by 3 you have to do a bit of approximating. For example 1/3 of 50mm is approx 17mm and twice that is 34mm, so the DX equivalent of a 50mm FF lens (nifty fifty) is ~ 35mm.

If you need a quick reminder as to which way round it is, just remember that the smaller DX sensor gives a narrower field of view - which is the equivalent of using more zoom. To get the same (narrower) field of view as a DX camera, a FF camera has to use more zoom, so the FF camera needs a longer focal length to give the same level of zoom.

Jan 13, 2021 04:03:31   #
User ID
 
R.G. wrote:
Starting with a DX focal length, the full frame (FF) equivalent is 1.5 times that. In other words a 100mm DX lens gives the same field of view as a 150mm FF lens.

Starting with a FF lens, the DX equivalent is 1/1.5 times that - which isn't a simple calculation but you can make it simpler. Multiplying by 1.5 (DX > FF) is the same as multiplying by 3/2, so going from FF to DX (the inverse of going from DX to FF) is the same as multiplying by 2/3 (the inverse of 3/2).

That's easy if the figure is easily divisible by 3 - for example 24mm FF is the equivalent of 16mm DX (1/3 of 24 is 8, so 2/3 is twice that, giving 16).

If the number isn't easily divisible by 3 you have to do a bit of approximating. For example 1/3 of 50mm is approx 17mm and twice that is 34mm, so the DX equivalent of a 50mm FF lens (nifty fifty) is ~ 35mm.

If you need a quick reminder as to which way round it is, just remember that the smaller DX sensor gives a narrower field of view - which is the equivalent of using more zoom. To get the same (narrower) field of view as a DX camera, a FF camera has to use more zoom, so the FF camera needs a longer focal length to give the same level of zoom.
b Starting with a DX focal length /b , the full f... (show quote)

Very tidy. Yet of no actual help for the intimidated masses. Nothing deficient concerning your math. But clearly, the real solution is to eliminate the math.

It just doesn’t matter how logical your explanation may be. It contains words such as “calculation, multiply, divisible, equivalent, and inverse”. IOW, dead in the water.

 
 
Jan 13, 2021 04:19:56   #
R.G. Loc: Scotland
 
User ID wrote:
Very tidy. But of no actual help for the intimidated masses. Nothing deficient concerning your math. But clearly, the real solution is to eliminate the math.


To go from DX to FF you just need to be able to divide by two. 1.5 is 1 + half of 1 (0.5), so for example 100 x 1.5 is 100 + half of 100 (50), giving 150.

To go from FF to DX you need to be able to divide by three then multiply by two.

If you want to be able to do that sort of conversion (which is what the OP was asking about), I can't think of a simpler way to describe it.

Jan 13, 2021 04:27:06   #
User ID
 
R.G. wrote:
To go from DX to FF you just need to be able to divide by two. 1.5 is 1 + half of 1 (0.5), so for example 100 x 1.5 is 100 + half of 100 (50), giving 150.

To go from FF to DX you need to be able to divide by three then multiply by two.

If you want to be able to do that sort of conversion (which is what the OP was asking about), I can't think of a simpler way to describe it.


Yes. And I did not disagree. I merely lamented the crippling pervasiveness of math phobia ... AND ... the insidious and pernicious insertion of math where it is not welcome nor needed.

The so-called “crop factor” is a useless nonissue. It is best ignored whenever it’s mentioned. Nothing is lost by banishing or ignoring it so why uphold the pretense that it really matters ? Just ignore it and it will go away.

Jan 13, 2021 05:36:57   #
BebuLamar
 
Your camera has the smaller DX sensor thus all lenses work the same on your camera.

Jan 13, 2021 07:30:02   #
WJShaheen Loc: Gold Canyon, AZ
 
We keep using the term "equivalent". But what may be going unsaid is, equivalent to what? (Sure, the math proves it but may not get the point across very well.)

The short answer is, equivalent to a 35mm frame. But, what's the point to comparing to something from the past?

Another perspective that helped me understand "crop factor" (and promptly forget about it) is to simply imagine an image on a sensor being projected onto either a screen of printed piece of paper of a given size. The smaller sensor's image must be stretched, or expanded to fill the final field of view, in effect zooming into the subject area. And, in the end, sacrificing some amount of resolution. But, again, when compared to a 35mm frame.

So, I am quite content with my DX format Nikon D7500. If I want more FOV, I just use a shorter lens.

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