Nikon crop factor clarification….

[adolfo.cruz]

I’m sorry to post this as I am sure this question has been put to rest, but I just want some clarification..

 

I have a Nikon z7 ii (FX) camera and when I recently put my Nikon 12-24 f/4 DX lens on it, I know I set it down to 12. But if you look at the exif data for the following image, it’s reporting it as 18.

 

From everything I’ve read and seen on YouTube, the 12-24 is always a 12-24, it never changes, only the imaging square is smaller, essentially the view. If you multiply 12 by 1.5, you get that 18 it’s reporting.

 

So my question is, am I not understanding what is being explained?

 

thanks..

 

[Dieter Schaefer]

This is what I see when I use my standard EXIF data viewer:

FocalLength35efl 12.0 mm (35 mm equivalent: 18.0 mm)

 

FocalLength 12.0 mm

FocalLengthIn35mmFormat 18 mm

 

So the focal length is reported correctly as 12mm - that doesn't change with the size sensor being used in the camera. Also reported is the ineptly named "35mm equivalent focal length", i.e. the "full frame equivalent focal length" that produces the same FOV as 12mm does on the cropped DX sensor but on the larger FX sensor - and that is 18mm. Why that information is there I don't know; for me it serves no purpose whatsoever.

 

Note that the camera switched to DX mode automatically and recorded an image of

ImageSize 5408x3600, i.e. some 19.5MP. Which is why you don't see vignetting in the above image - which would result of the 12-24 image circle not filling the FX sensor fully at its 12mm setting. IIRC, then the 12-24 can be used in FX mode for settings larger than 18mm (i.e. at 18mm and beyond the lens image circle encompasses the entire FX sensor).

[adolfo.cruz]

Mr. Shaefer, thank you for your response. I thought I was going crazy. ;)

 

Any other comments welcomed.

[httpwww.photo.netbarry]

Same happens on my Fuji using a Fuji lens. Program reads the info from the lens as 23mm and then gives its crop factor equivalent as 35mm as the camera uses an APC sensor. It's common and normal.

[glen_h]

My favorite (OS X Preview) says:

 

File Source: DSC

Flash: No Flash

FNumber: 14

Focal Length: 12

Focal Length In 35mm Film: 18

Focal Plane Resolution Unit: centimeters

Focal Plane X Resolution: 2,301.325

Focal Plane Y Resolution: 2,301.325

 

So it specifically mentions 35mm film.

 

But I do wonder about the "Focal Plane X Resolution", and especially

that the unit is in cm. Shouldn't the unit be 1/cm?

[rodeo_joe1]

But I do wonder about the "Focal Plane X Resolution", and especially

that the unit is in cm. Shouldn't the unit be 1/cm?

It seems clear to me that if the unit is centimeters, then the reported resolution is xxxx.xx pixels-per-centimeter. And if the unit was to be switched to inches, then the resolution would be reported in pixels-per-inch.

 

In this instance the 2301.325 pixels-per-cm scales up to 3682.12 by 5523.18 pixels (20.34 Mp) over the 1.6cm x 2.4cm DX format. With no need to use reciprocal units at all.

 

The only wierdness is why fractions of a pixel result, when they can't possibly be physically shown.

[q.g._de_bakker]

Pixel per unit is the same as pixel/unit, or pixel × 1/unit.

 

Fractional pixels only result if you take the pixel per unit spec as exact instead of what it is: nominal.

[rodeo_joe1]

Pixel per unit is the same as pixel/unit, or pixel × 1/unit.

No. The number of pixels per unit is multiplied by the frame size in whatever units. Not divided by it.

 

The pixel number per frame height in the above case is 1.6(cm) x 2031.325.

Pixels x 1/unit would be 2031.325/1.6 - completely the wrong result.

Fractional pixels only result if you take the pixel per unit spec as exact instead of what it is: nominal.

So giving a nominal value to 3 (incorrect) decimal places isn't wierd?

Edited January 15, 2022 by James G. Dainis

[q.g._de_bakker]

No. The number of pixels per unit is multiplied by the frame size in whatever units. Not divided by it.

Yes, the total number of pixels per sensor is the result of multiplying the sensor dimension by the numder of pixels per unit of length.

So what?

 

And you were totally wrong in what you said about that, not needing a reciprocal value. It is a reciprocal thing.

 

And who gives nominal values to 3 decimal places?

Edited January 15, 2022 by James G. Dainis

[Gerald Cafferty]

I'm pleased we've cleared all that up, just looked out the window it's a bit foggy here also.

[JDMvW]

And who gives nominal values to 3 decimal places?

 

i just happened on this statement.

 

Could the answer to this mystery be "engineers" :rolleyes:

 

(for example see

)

[rodeo_joe1]

Reminds me of the mythical patent application for an anti-gravity perpetual-motion device that goes: "It is well known that cats always land on their feet, and also that buttered toast always lands butter-side down. Therefore this application proposes a device consisting of one domestic feline in combination with a strong harness for the purpose of holding a slice of buttered toast facing butter-side up on the back of said feline. Thus, when dropped from a height of a few feet, the combination will have opposing forces acting upon the cat's feet and the butter layer of the toast. Thereby the nett resultant of the opposing forces will induce a spinning motion in the cat/toast combination allowing it to levitate above the ground indefinitely."

 

That video also omits to mention the aura of sadness induced around the owners of multiple cats, and the negative impact on surrounding birdlife by the evil little b*st*rds (I mean the cats, but their owners are ultimately to blame!).

 

Also, the limit of two million petabytes of internet data allocated to cat-related postings has just been exceeded. Further postings on the subject may result in a hefty fine, or prison sentence for persistent offenders.

Edited March 11, 2022 by rodeo_joe|1

[glen_h]

 

In that case, here is a picture of a cat from a Nikon D200 with crop sensor.

 

And what it says in its EXIF data:

 

Color Space: sRGB

Components Configuration: 1, 2, 3, 0

Compressed Bits Per Pixel: 2

Contrast: Normal

Custom Rendered: Normal process

Date Time Digitized: Dec 5, 2013, 21:01:20

Date Time Original: Dec 5, 2013, 21:01:20

Digital Zoom Ratio: 1

Exif Version: 2.2.1

Exposure Bias Value: 0

Exposure Mode: Auto exposure

Exposure Program: Aperture priority

Exposure Time: 1/80

File Source: DSC

Flash: No Flash

FlashPix Version: 1.0

FNumber: 4.5

Focal Length: 180

Focal Length In 35mm Film: 270

Gain Control: High gain up

ISO Speed Ratings: 3,200

Light Source: unknown

Max Aperture Value: 0

Metering Mode: Spot

Pixel X Dimension: 3,872

Pixel Y Dimension: 2,592

Saturation: Normal

Scene Capture Type: Standard

Scene Type: A directly photographed image

Sensing Method: One-chip color area sensor

Sharpness: Normal

Subject Distance Range: unknown

Sub-second Time: 32

Sub-second Time Digitized: 32

Sub-second Time Original: 32

User Comment:

White Balance: Auto white balance

AFInfo: 0.469, 0.465, 0.062, 0.069, s, 0.472, 0.692, 0.057, 0.046, n, 0.472, 0.262, 0.057, 0.046, n, 0.311, 0.458, 0.031, 0.085, n, 0.658, 0.458, 0.031, 0.085, n, 0.311, 0.581, 0.031, 0.085, n, 0.658, 0.581, 0.031, 0.085, n, 0.311, 0.335, 0.031, 0.085, n, 0.658, 0.335, 0.031, 0.085, n, 0.191, 0.458, 0.031, 0.085, n, 0.778, 0.458, 0.031, 0.085, n

Flash Compensation: 0

Focus Distance: 0.01

Focus Mode: One-shot AF

Image Number: 18,560

Lens ID: 1

Lens Model: Manual Lens No CPU

 

I am not sure now which lens this is, as I don't have a 180mm non-zoom lens, and might

not have been good at setting the manual lens data.