Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

Not simplistic at all - it's common sense vs technobabble. Except for the part about dot accuracy being dependent on the ink nozzle, which is only part of the story. The stepper motors that advance the print head and paper can produce ink dot placement accuracy that is less than a full dot, which is what an Epson that has a native resolution of 360 ppi produce images with a "resolution of 2880x1440. Also, Epson and other printer mfgrs use a variable dot pitch in conjunction with highly precise dot placement to further enhance "resolution" in their printers.

CatMarley Loc: North Carolina

My point was that the number of variables involved between the front of the lens and the print on the wall are too great to make a binary statement of which gives more advantage - lens length or sensor size.

imagemeister Loc: mid east Florida

If you do not mind spending the 2X-5X money and carrying the weight/management of the longer/slower lens - will it provide a definitively "better" image ?? ( in all scenarios)

OR, will the new high density sensors and cropping with pixel enlargement/software be "good enough" for the rest of us ?? - It IS good enough for me......

Apaflo Loc: Anchorage, Alaska

But you can't actually print the original 6000x4000 pixel image at 240 PPI, because there are no printers with a native rate of 240 Pixels Per Inch. Canon and HP print at 300 PPI and Epson prints at 360. So to print an image that has 6000 pixels across at 25 inches wide the image has to be resampled, interpolating 360 pixels for each original 240 pixels to get a 9000x6000 image. The resampling has a negative effect on how the fine detail of an image is seen when viewed because the size of the print was increased, but there isn't more actual detail (hence in effect the "resolution" of the image is reduced).

To compare print sizes as a measure of resolution you have to specify the printer, and stick with the actual PPI rate the printer uses. Resampling interferes with easy comparisons.


Yes there are many things that affect resolution. But you always have to start with the sensor's pixel rate, because that sets the maximum resolution that can be captured. No matter how sharp the lens, how close you get to the subject nor how much detail there is in the scene, the maximum resolution is limited to what the sensor can record. (See the Nyquist-Shannon Sampling Theorum.)

Hence the D7200 camera with a limit of 127 lp/mm, at the same distance and using the same lens, can record finer detail, if it exists in the scene, than can a D810 camera that has a limit of 102 lp/mm. In practice what we do is change the spatial frequency of the image detail that is projected onto the sensor. Getting closer to a picket fence makes the pickets larger and farther apart. That equals lower spatial frequency and requires lower resolution to capture accurately. Using a longer focal length lens has the exact same effect.

Consider that a Nikon D4 has an even lower resolution sensor than the D810. The D4 can only record 68 lp/mm. Hence if we have a 50mm lens and take a picture of the white picket fence around a house from a distance of 2000 feet, none of those cameras will be able to capture the detail in the pickets which will be just a white blur. If we move up closer there is some point at which the D7200 image will just barely show the detail of the pickets, but the others won't. If we get up very close, even the D4 will clearly show the individual pickets.

We could move to the distance where the D7200 is just showing detail with a 50mm lens, and then put a 600mm lens on the D4 and get better detail in that fence than the D7200 with a 50mm lens can capture. But with both distance and focal length what we have done is not really increase the resolution of the data recorded, but rather we have reduced the spatial frequency to where it is low enough to be recorded by each of those sensors. The higher the resolution of the sensor the less change to the spatial frequency required.

That is why the D7200 is the choice if you are "focal length limited" and can't move closer to a subject. That is commonly the case for bird photographers, or even those shooting other kinds of wildlife. A D810 with lots of pixels for large prints is nice, but you can't print fine detail that was not captured by the sensor in the first place.

CatMarley Loc: North Carolina

The 240 dpi was a "for instance". One of many variables. And the sensor capture of detail will depend on how the sensor deals with the light the lens sends it, and what filtration is being done at the sensor surface as well as the sensor element layout as well as the number of elements or their density and size. Because of the many variables, you are never going to get "maximum" anything. It is always going to depend on the specific set of variables involved and never can be resolved to a binary choice of lens length v sensor size.

Apaflo Loc: Anchorage, Alaska

But it is not a valid variable. Or perhaps I should say it is a very very misleading concept when discussed in those terms. The best thing, as suggested, is just use the actual PPI of a given printer.

But the limit is not arbitrary, and it is not the same for every camera. It is the pixel density of the sensor that sets that limit. The D4 is limited to barely more than half the resolution of a D7200. It makes no difference what all these other variables are, the "binary choice" is that to use a D4 instead of a D7200 clearly binds a photographer in that way.

Just as clearly, if the photographer is not focal length limited, but needs to shoot high frame rates at high ISO settings (shoot basketball, or a boxing match) then it is a very simple binary choice to use the D4 instead of the D7200. Not a resolution issue, but still a binary choice that just happens to be the opposite of what a wildlife photographer would make based on the resolution criteria.

These binary choices start with the decision on which camera to buy in the first place. Or for that matter which brand of camera to buy. The choice is perhaps of very little consequence to those who for whatever reason are not critical of the results. But there is a reason that so many high end photographers own multiple cameras, and even multiple brands!

par4fore Loc: Bay Shore N.Y.

Thanks, a lot of great information and input from all.