Silverman Loc: Michigan

I am almost sure, but not positive, that the 1.5 multiplication factor concern the DX model Camera, specifically how the Sensor size affects the actual F.O.V. of the lens you have on the Camera.
So, with a Nikon 50mm AF-S Lens on a DX sensor body, (ex. Nikon D3300), you would multiply length of lens,(50mm) x 1.5 = 75mm F.O.V.

This is my understanding, if it is incorrect for any reason, please correct my understanding of this controversial subject. I will look forward to all feedback on my above understanding of this subject.

PHRubin Loc: Nashville TN USA

It IS the focal length (which has to do with lens dimensions) stated on the lens.

Because the sensor in a DX body is smaller than one in an FX it "sees" an area of view 1/1.5 times smaller than the FX body would, or as an FX body would see with a lens of focal length 1.5 times larger. It is what it sees, or the field of view, or crop factor, that is 1.5 times. Other characteristics are as the stated focal length would indicate.

JD750 Loc: SoCal

Yes you have got it. The next question to ponder is does the change in sensor size have any effect on DOF?

selmslie Loc: Fernandina Beach, FL, USA

Of course it does. Any DOF calculator will demonstrate that.

But all of the DOF calculators and hyperfocal distance values apply only to an un-cropped image.

As I pointed out earlier, simply cropping an image after it is captured changes the DOF and it also changes the hyperfocal distance.

JD750 Loc: SoCal

Yes I know, but my question was meant for OP, to give OP something think about, as he was an engineer and likes to know how things work.

Wmetcalf Loc: Rogersville, Mo

its cropped but not enlarged

selmslie Loc: Fernandina Beach, FL, USA

Of course the DX image has to be enlarged. So does the FX image.

Unless you are comparing an image 1x1.5 inches (FX) to an image that is 2/3x1 inch (DX) with a magnifying glass, you are looking at enlarged images.

If you make a 4x6 inch print from each image, the FX gets enlarged by 4x and the DX gets enlarged 6x (approximately).

JD750 Loc: SoCal

I think wmetcalf meant to say not magnified, rather than not enlarged.

Yes you are of course correct in pointing out all images are enlarged as the camera sensor is much smaller than the LCD, computer screen, prints, etc. The pixels are really tiny. ;)

selmslie Loc: Fernandina Beach, FL, USA

That sounds like a distinction without a difference.

Rather than put words in his mouth, let's see if he can clarify what he meant.

JD750 Loc: SoCal

Fair enough.

lamiaceae Loc: San Luis Obispo County, CA

Just ignore it, you'd be better off. Learn what each lens you do own does for you. Thinking in 35mm film camera lens wise is only for and only makes any real sense to those of us who have used 35mm film cameras and lenses for any years. No one thinks "what is the crop factor for using a 210mm lens on a 4x5" view camera." I can't even imagine Ansel Adams or Henri Cartier-Bresson considering that relative to a 35mm film camera. Or even more applicably a Schneider Symmar 120mm vs a 120mm Super-Angulon lens? (same focal length, different angles of view for the same camera.)

dcampbell52 Loc: Clearwater Fl

But the other side of that is (and I run into this with my Full frame D610 vs my Crop Sensor D7100) I am more careful about cropping/framing with the DX than I am with the FX... Translated meaning that I often find that I am getting images that I am more inclined to use more of and crop less in shots made by my DX and more inclined to crop my FX images to something similar to what I shot in DX. Having said that, I carry 2 cameras most of the time (the DX D7100 and the FX D610) and I keep a wide (12mm) to normal (50mm) lens choice on the FX and a normal (the 50mm which would translate to a roughly 75mm) to zoom telephoto (80-400mm which translates to roughly a 120-600mm) on the DX... Now keep in mind that your are giving up some DOF on the DX or you are going to shoot aperture or manual (which I generally shoot anyway so that I can control the DOD) but this arrangement is what works for me. ALL of my lenses are FX lenses so that I can use any of the lenses on either camera. I just have to remember that I am "pre-cropping" with the D7100 and loosing some DOF. But, I should point out that I end up with similar results to what I would have if I was shooting the FX with a 1.5 teleconverter on my lenses, but I have the convenience of two cameras which radically reduces my lens changing and missing a shot because I was "between" lenses. Personally, I like having 2 separate cameras (one FX and one DX) as it gives me immediate choices and I miss very few shots. Sure, I do have to lug the added weight of a second camera body (I would carry the lens anyway) but I pay for that inconvenience with being able to switch cameras almost immediately and I have 2 64gb SD card in each camera.

berchman Loc: South Central PA

The teleconverter would bring the object closer like using a more powerful pair of binoculars, but the DX does *not* bring the object closer; it only has a narrower field of view. I used to make this same mistake too.

dcampbell52 Loc: Clearwater Fl

I understand that but was trying to give an "easy" example for describing the result. Actually, a DX camera is only recording 2/3rds of the same image that an FX camera would. So, ideally, the photographer is framing his/her shots tighter. I have found that if I am shooting my FX camera, I often shoot a wider image but end up cropping that image in Lightroom to an image that I probably would have shot in DX anyway. However, there are 2 distinct disadvantages to DX that are plusses for FX. Your Depth of field (focus area) is tighter (narrower) in DX than it would be in FX.. I guess what I mean is that if I shoot an image at f22 in DX the focus zone (area in focus at any given f/stop) is narrower.. a shot at 50 feet at f/16 on the DX might have everything from 40 feet to 60 feet in focus... where that same shot on an FX camera might have everything from 35 feet to 65 feet in focus. Please note that these are approximations for illustration and not necessarily accurate. I use a Depth of Field calculator for precise calculations.. (I have it on my cell phone). So, I tend to use each camera to its best abilities. I shoot FX for landscape, wide shots, etc. and shoot DX for moderate to long shots. I keep a telephoto zoom on the DX and either a 50mm or a 35mm on the FX. And yes I can always shift the FX to DX mode.. but why. If you shift to DX then you almost always forget to shift back to normal.

Tronjo Loc: Canada, BC

David,
With all due respect, your statement about the DOF vs. sensor size relation is correct only for one specific case: Identical distance to subject, physical focal length and physical F#.
There are other cases though, (like identical distance to subject, effective focal length (FOV) and physical F#) where the opposite is true: the larger sensor delivers shallower DOF.
The best article on the subject I have ever read is this one: https://photographylife.com/sensor-size-perspective-and-depth-of-field.

There are numerous DOF calculators out there and many give different results at same input parameters, probably because they assume different shooting conditions and / or different CoC definition.
Happy shooting