Greer Loc: SOUTH GEORGIA

I want to figure thr number of mega-pixels I’ll be dealing with in DX mode on my D850. So, do I divide the 45mp of the D850 by 1.5, meaning the resulting DX equivalent image contains 30mp? Is their a formula for this? The formula is what I’m looking for. Thanx.

CO

Going by the chart you would have 19.4 megapixels in DX mode.
FX: 8256 x 5504 = 45.5 megapixels
DX: 5408 x 3600 = 19.4 megapixels

I don't know how Nikon is arriving at this. If going by the overall dimensions of a full frame sensor (864 square millimeters) and Nikon DX (368.16 square millimeters), you would have about 15 megapixels is DX mode.

The 1.5x crop factor is derived from the diagonal measure of the sensors. A full frame sensor has a diagonal measure of 43.26 millimeters. A DX (Nikon) sensor has a diagonal measure of 28.29 millimeters. 43.26 divided by 28.29 is 1.53.

(Download)


(Download)

Jerry G Loc: Waterford, Michigan and Florida

The fx to dx crop factor is 1.53, it's just rounded to 1.5 for convenience.

CHG_CANON Loc: the Windy City

Read the manual. Page 91 of the D850 user manual has a 1-page chart of all the pixel sizes the D850 can create, including the DX cropping format.

larryepage Loc: North Texas area

Crop factor, a term which in my mind should never have been spoken or written, is a linear adjustment. As mentioned, it is applied to the diagonal, the length, and the width of the frame. But pixel count, in this case, is tied to the area of the frame. That means that you have to apply the crop factor twice...once to the length and once to the width. 1.5 x 1.5 = 2.25. Using that number, 46.5 ÷ 2.25 = 19.4 (or so).

A quick look at the frame dimensions tells you that's about right...DX is a little smaller than one end of an FX frame if you cut it in half...like the old Pen-F half frame cameras.

Greer Loc: SOUTH GEORGIA

Thanx Larry. That’s what I was missing. Dividing twice by 1.5, if you could call that a formula. Makes sense now as to my question, as I was trying to establish how Nikon came up with their 19-20 MP’s. And I’ve read some who say it’s as little as 10MP and upward to 30MP when using DX mode. 😎 Have a great day.

amfoto1 Loc: San Jose, Calif. USA

Your math doesn't work. The easiest way to estimate it is to determine what percentage of AREA will remain, going from full frame to DX (15.6x23.7mm = 370 square mm).

Full frame image area: 24 x 36mm = 864 square mm.

DX sensor image area: 15.6 x 23.7mm = 370 square mm.

370 divided by 864 = 43%

Multiplying 45MP by 0.43, I would expect to end up with around 19MP.

BUT, for some reason Nikon says the D850's DX mode makes for 15MP images. I don't know if or why there's this discrepancy.

15MP isn't bad. But it's not particularly great either, considering a current Nikon DX camera offers 21 to 24M. (i.e., D500, D5600)

However... DON'T DO IT!

There are several good reasons to NEVER use DX mode on your D850 (unless you happen to be fitting a DX lens to it).

1. Doing the crop in post-processing instead will give you EXACTLY the same results!
2. Doing the crop in post-processing instead will allow you to reduce the crop or not do it at all, if you decide either would be better.
3. Doing the crop in post-processing instead will allow repositioning the crop if you wish, where the in-camera crop will always only be centered.

So there's really no good reason to do DX crops in-camera (unless using a DX lens).

BebuLamar

Nikon said in DX format it's 19.4MP.

Paul Diamond Loc: Atlanta, GA, USA

In other words, don't do it. Shoot full frame RAW. Crop if you must for the subject/distance, if you must. And look at the best image you can make. Don't worry or think about the math. Only the final picture matters - not some textbook math that no one will look at.

I.E. - Make the best picture you can with the equipment you have, at the distance you are forced to shoot. And be happy with the results you can achieve using PP. Or, look to refine your optics and/or PP software, or use a 'duck blind' to give you something more at these working distances. (I own a D850.)

amfoto1 Loc: San Jose, Calif. USA

You're right. I just looked at the D850 specs on the Nikon USA website.

What I mistakenly quoted was the movie DX mode resolution. Got that wrong too... It's 16MP, not 15MP.

None-the-less, I stand by the rest of my response. It makes little to no sense to use the DX mode and do in-camera cropping during "normal" still photography. The exact same thing can be accomplished in post processing, while leaving you options to make changes if you wish. One possible exception would be if using a DX lens on the camera. But, even then, while the lens may vignette heavily it still will likely produce a larger image circle and be better to do the crop in post, where you have opportunity to change the crop by making it larger or repositioning it. You give up that flexibility any time you do the crop in-camera.



And, I fully agree with Paul. It will always be better to avoid cropping as much as you can. Yes, a 46MP camera leaves you some room to drop if necessary. But unless you simply can't get any closer for some reason (dangerous subjects or shooting from a restrictive location with the longest lens you've got), do the best to "fill your viewfinder" and make full use of the entire potential of your camera's sensor.

BebuLamar

I agree with you about not doing it in camera. Do it in post you have more options.

larryepage Loc: North Texas area

There are also other setup options to trade off resolution for smaller file size on the D850 while still using the same frame size if you don't want to go to a smaller frame size.

Let's be honest here. ..some photographs just don't call for 46MP. I realize that memory is relatively cheap today...I just bought 16GB of RAM for a laptop for $92...but that still doesn't make every image worth the big file, except perhaps in an over-developed ego.