Nikon NX reduces file size when sharpening?

[sandiegojoey]

I just noticed that each time I sharpen a jpeg image using the "unsharp mask" tool in Capture NX, it reduces the file

size by almost 50%. I have to admit that I'm not sure I'm doing this right to begin with. I'm shooting my daughters

Field Hockey games with a Nikon D3 and 70-200mm f/2.8VR in A priority and Auto ISO (JPEG mode). The images

are coming out great, with one exception, I'd like them to look a bit sharper.

 

When I open them using Capture NX they look a littel soft (even though I crank up the sharpening in the camera).

They seem to look better (at least on my monitor) when I use the Unsharp Mask tool. The tool has three sliders,

Intensity, Radius, and Threshold. Each time I open the tool, the Radius slider is automatically set at 5% while the

other two are at 0%. When I slide the Intensity bar to the right at about 60%, the image looks much nicer on my

monitor and I assume with look the same when I print, so I leave the other two sliders alone and save. However, my

JPEG image will go from 5.8MB down to 3.2MB just from that function alone. If I want to crop on top of that I end up

with 1mb images!

 

Where is that information going? Am I actually degrading the quality of my images when I do that? I upload them to

Costco for parents to print and I'm concerned that the reduced file size will not allow quality 8x10 prints or even

larger.

 

What, if anything am I doing wrong?

 

thanks.....Joey

[sandiegojoey]

...it's me again. I just tried another test, this makes things more confusing (at least for me). I just cropped an image, did nothing else to it, and saved it. The file was reduced from 5.7MB to 1.7MB as I'd expect. I then applied the sharpening tool in the way I explained in my original post, however, this time the file size increase to 4.9MB! Why the difference?

[bruce_margolis]

Joey, I don' t have a clue why the change in file size but if I were shooting JPEGs, I would simply adjust the sharpening in-camera. If you are otherwise happy with your shots and they don't need any post processing, why use NX simply for sharpening? Try it and see what it does to your image quality and file size.

[Carl Stone]

First Capture NX is meant for post processing raw images, not jpegs. The worst sharpening occurs in camera, and the best

is done as a last step in post processing. If you're going to shoot jpegs, NX is pretty much worthless to you. When you

shoot jpegs, what you see is pretty much what you get. Shooting raw gives you control over the image that jpeg cannot. If

you nail the shot using jpeg, great, but if you need to edit it after it's shot, then you need to shoot raw.

 

The size of any digital image is going to be judged by the subject matter. A shot of a clear sky will produce a smaller file

than a shot of a wheat field. That is why you see a variance in file size.

[rene gm]

I tried the same in Photoshop CS3 and the file size actually increases after sharpening, which is what I

would have expected.

 

The explanation might be, that Capture NX uses a different compression than the camera. To test, save

a file with and without sharpening.

[twmeyer]

Are you working from a compressed NEF (16bit) and saving as a JPG (8bit) with higher compression? Are you

measuring the file size when it is closed, or when you open the file in editing software like Photoshop or

Elements?<p>

 

Open the file in your editing software and check its resolution (ppi) and it's actual dimensions. Are they same

in both the pre and post edited files?<p>

 

An 8bit jpg, when open will be half the size of a 16bit NEF or tif file, yet have the same resolution and

dimensions... t<p>You have double posted this question which causes trouble

[claudio_di_martino]

First thing that comes to mind is that JPEG is a lossy format and that you decide the tradeoff between

compression and quality. Probably when saving (I don't know Capture NX) the software uses some default preset

that doesn't match the camera level of quality. You should look for an "advanced option" button in the save

dialog or modify some global setting in the program itself and set it at 100%, maximum or whatever it is the best.

 

Another point is that, given a quality setting for saving the JPG, the more detail is present in the image the

bigger the jpg gets.

You can experiment this "feature" by yourself with this simple experiment. Use manual focus and take photos of

the same subject incorrectly and correctly focused. Then compare file sizes and for sure the properly focused one

will be of much bigger size. The same works for shaky photos. If shooting in low light hand held with long

exposures, take a burst of photos and then keep only the biggest one... this simple euristic will always choose

the steadier one from the burst.

 

As for the assumption that images with sharpening adjusted on screen will look the same on print, it's incorrect.

Sharpening should be adjusted for the print size...

 

Ciao!

 

Claudio