# Help understanding "effective pixels" vs image size?



## TexasPilot (Jan 27, 2018)

Operating System:Windows 10
Exact Lightroom Version (Help menu > System Info):  CC - up to date

Good Evening:

I use a Nikon D850.  The specs are that the sensor is 35.9 mm  x 23.9 mm.  The specs state that the "effective pixels" are 45.7 million.

When I import to Lightroom my images are 7372 x 4920 = 36.2 million.

Why is there a difference - and even more importantly, why does it matter?

I take a lot of farm and ranch images that are often at a bit of a distance and enlarging is a big facor for me.

Many thanks for San Antonio, TX.

Ed


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## Hal P Anderson (Jan 27, 2018)

Total and Effective Pixels - What Digital Camera

Why you only have 36.2 megapixels is a mystery. Are you sure you have a D850? Those pixel dimensions are what a D800 and D810 produce.


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## clee01l (Jan 27, 2018)

There are setup modes that reduce the effective pixels in the D800/D810 to 24mp.  I expect there is a similar setting in the D850.  Check your camera set up.


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## happycranker (Jan 27, 2018)

As well as checking the image area settings, if you use DX lenses on a FX body there is a setting which will crop automatically!


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## Linwood Ferguson (Jan 27, 2018)

And just to be clear to your original question, LR pixels should match effective pixels.


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## Hal P Anderson (Jan 27, 2018)

Nikon | Imaging Products | Nikon D850

None of the many pixel dimensions mentioned in that website match what the OP is seeing. None are even close. 

However, here's a post from DPReview that seems to indicate that the OP's dimensions are exactly what Adobe recovers from a raw file from a D800 (and probably from a D810 since they share the same sensor):

_chuxter • Forum Pro • Posts: 21,713 

 Re: D800 real image size ? EDITED ! 

 In reply to JP Scherrer • Oct 24, 2014 

I processed a NEF file from my D810 with the Adobe DNG Converter, Version 8.6.0.254. I then ran that DNG file by DNG Recover Edges. When I did a small window popped up that announced it had successfully recovered 117,900 pixels.


I then looked at both an unrecovered and recovered version using Windows Explore [hovering over the image thumbnail or file name will cause a box to drop down with the dimensions]:

_

_Unrecovered = 7360 x 4912_
_Recovered = 7372 x 4920_
_ 
Doing the math, the border is 6 pixels wide on the "ends" and 4 pixels wide on the "sides". Continuing w/ 5th grade math, I computed the number of extra pixels recovered as 117,920. This means that Thomas can't do 5th grade math. 


I next wondered what other editors would report. Both Faststone and XnView report:

_

_Unrecovered = 7380 x 4928_
_Recovered = 7372 x 4920_
_ 
This implies that they think the borders are 10 px x 8px prior to being "recovered".


I do not know why Adobe only recovers 6 px x 4 px?_


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## TexasPilot (Jan 28, 2018)

Hal P Anderson said:


> Total and Effective Pixels - What Digital Camera
> 
> Why you only have 36.2 megapixels is a mystery. Are you sure you have a D850? Those pixel dimensions are what a D800 and D810 produce.



Well folks, what you just got from me was a serious case of delusional _*"sensor envy"*_  - I have a Nikon D810, and _I have absolutely no idea why I thought I had a D850!_   My sincerest and humble (humiliated) apologies.   Will do better next time.

As an FYI, what I was trying to do was to get a better understanding of the issues surrounding enlarging images for printing.   I may need to provide someone with a 60" x 40" print and I just do not have the experience or background to know what is possible.   

Kindest regards -

Ed


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## TexasPilot (Jan 28, 2018)

clee01l said:


> There are setup modes that reduce the effective pixels in the D800/D810 to 24mp.  I expect there is a similar setting in the D850.  Check your camera set up.


Well folks, what you just got from me was a serious case of delusional _*"sensor envy"*_  - I have a Nikon D810, and _I have absolutely no idea why I thought I had a D850!_   My sincerest and humble (humiliated) apologies.   Will do better next time.

As an FYI, what I was trying to do was to get a better understanding of the issues surrounding enlarging images for printing.   I may need to provide someone with a 60" x 40" print and I just do not have the experience or background to know what is possible.   

Kindest regards -

Ed


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## clee01l (Jan 28, 2018)

A 60"X40" print can be made BUT the resolution will be limited to no more than 122ppi. Depending on the image, an acceptable print can be achieved.  I have a beautiful 30"X24" canvas print that was made from a severely cropped D810 image.  The resolution on that is 109ppi.


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## Hal P Anderson (Jan 28, 2018)

Large prints are typically viewed from a distance where the individual pixels won't show at 122 ppi. You ought to be fine.


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## Linwood Ferguson (Jan 28, 2018)

Usually they are not viewed close up, but people who make really large prints often smooth out the pixels as part of the printing so if you do get really close you may not have the detail, but it does not look like a zoomed-8-times view on your monitor where you see huge pixels.

A school did these rather large prints from what were often smallish crops from lower resolution cameras (D5, D4 mostly).  I was very surprised that I could walk up and look at a few inches away and not see large grain.  i did not see fine detail of course, but it did not look like some over-zoomed mess either.

Use a quality lab and follow their recommendations and I suspect you will be pleasantly surprised.  Bear in mind a D810 is still one of the 3-4 highest resolution DSLR's, so it is not like you are trying to do something with inappropriate gear.

Linwood







PS. Full disclosure only 8-9 or so of them are mine.


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## TexasPilot (Jan 29, 2018)

Ferguson said:


> Usually they are not viewed close up, but people who make really large prints often smooth out the pixels as part of the printing so if you do get really close you may not have the detail, but it does not look like a zoomed-8-times view on your monitor where you see huge pixels.
> 
> A school did these rather large prints from what were often smallish crops from lower resolution cameras (D5, D4 mostly).  I was very surprised that I could walk up and look at a few inches away and not see large grain.  i did not see fine detail of course, but it did not look like some over-zoomed mess either.
> 
> ...



Great work!    Great advice.   I am considering using Miller Labs for the 36 x 48" canvas.


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