Do I need to use sharpening in this case?

[agarwaldvk]

Hi Everybody

This is my first post on this forum. I consider myself a newbie when it comes to digital image processing but my desire and endeavour is to gain reasonable knowledge in this area of activity - it is my hobby and I don't intend to to anything professionally as such - may consider it after retirement, who knows?

I normally shoot with my Nikon D40 DSLR (6.1 mp) camera. The images are pretty good at (I think and I could be wrong here) 3008 pixels * 2048 pixels. The default resolution is 300dpi (as shown by Photoshop -> Image size dialog box).

The intent is in most instances (there is one exception to this that I shall come to later - I think I will put it in a new thread since it is in a slightly different vein) is to print the image (H * W) in 4 in * 6 in (or 6 in * 4 in) size - this then becomes the canvas size. This size includes 0.5in white border for caption. This essentially means that the image size is 3.5 in * 6 in (or 5.5 in * 4 in) size.

This is what I do in Photoshop :-

1. Open Image
2. Save as TIFF format
3. Change image size by going in to : Image Size -> 3.5 in * 6 in (or 5.5 in * 4 in) without resampling
4. Crop to above size
5. Write Caption
6. Save as TIFF
6a. Filter->Sharpen->Unsharp Mask
6b. Save TIFF
7. Save as JPG at Quality 12 and Progressive Scan (Space is not the issue here, I am not trying to save the space here at all)

All of this works fine. I have been reading a bit on the net about digital image processing including resizing of digital images and I have learnt that it is advisible to use (in Photoshop) Filter->Sharpen->Unsharp Mask to sharpen the image after resizing an image (both down and up sizing preferably using Bicubic Smoother/Sharpner in respective cases). I tried that as well. What I noticed was that there was some sharpening that was done. When viewed on screen at 200%, this sharpened image (as compared to the unsharpened one - the only difference being steps 6a and 6b are not performed), the image looks sharper than is should be - this is at 200% on a 22in wide screen monitor.

I can understand that when image is enlarged (for larger prints) with/without resampling, there could be a need for sharpening and there would ordinarily be some loss of detail/quality/sharpness. But what I am having difficulty understanding is that when you are actually reducing only the print size (without resampling) should there be any loss of detail/quality/sharpness and hence should there be a need for sharpening? If anything, in this instance, since the pixel content of the image is the same, and dpi has consequently increased, the image, both on screen and on hardcopy print, shouldn't have any loss of quality/detail/sharpness and hence should look better, shouldn't it?

So, in what I am trying to do, do I need to Filter->Sharpen->Unsharp Mask?



Best regards



Deepak Agarwal

[OsmosisStudios]

This is all very subjective, but how about some examples?

[agarwaldvk]

OsmosisStudio

Thanks for your response.

I do understand that there is a huge amount of subjectivity when it comes to personal preferences on photos/images.

You want me to put some of the images in here? Mate, the only problem with that is that the tiff files are 15 mb each and to put 2 of those - one with and one without sharpening would be a lot space just wasted. I can however attach the jpg versions of those (2.7 mb each at highest resolution) if that is going to help. I will do that when I get home tonight. If space is not the issue, I can attach the tiff files as well. Please advise!

However, my initial enquiry was with reference to pure theoretical aspects of post processing - essentially saying that when the physical dimensions of an image is reduced from say 10" by 8" to say 6" by 4" without resampling, that is, without loss of any pixel (I take this to imply 'without loss of picture quality/sharpness/detail'), then would it still necessitate sharpening. In other words, when there is no loss of sharpness as a result of some post processing, then would it still be warranted to sharpen the image?

Or is this only to counteract the anticipated loss of sharpness as the image is finally saved as a jpg?

I certainly will try and attach the sample files this evening - if it is too big then I will crop just the face part and attach that - just for your immediate reference.


Best regards



Deepak Agarwal

[oxfordy]

Originally Posted by agarwaldvk

Hi Everybody
So, in what I am trying to do, do I need to Filter->Sharpen->Unsharp Mask?
Best regards
Deepak Agarwal

Well, 'yes' and 'no'. (helpful eh?)

- Most digital images need sharpening.
- Preferably sharpening should be something you do late in your workflow.
- some (most) cameras default to doing some sharpening 'in camera' - you would be sharpening twice if you also did it in software - beware.
- If you resample an image you should sharpen after the resample (however, you are not resampling, just changing the dpi setting - so no sharpening necessary for this)

For best results, I turn off all sharpening in camera (if you shoot jpg this may not be possible), download the image and process (including any resampling) then sharpen and print.

If your camera is doing some sharpening, then generally I would not add to it unless you have resampled the image (which you are not).

Others will undoubtedly have different approaches.

[agarwaldvk]

Hi Oxfordy

Thanks for your response.

One thing is now hopefully clarified in my mind without any doubt (I think) - that, as in my case, I am only changing (increasing) the dpi (without resampling, that is), as such, there is no need for sharpening.And since the original image from the camera was a jpg, some sharpening would have anyway been done in it anyhow! Got that!

The output that I get from my D40 using the 18-200 mm AF...VR Nikkor lens in the jpg format is generally very good - I take it that, as you said in your post, there would already be some sharpening that would have been done by the camera itself, so I don't really need to worry about it.

I haven't tried taking RAW photos yet from my camera (I am assuming that it can) but want to - just to see what is the real benefit this format offers over jpg. I have cursorily read that I would need some spe******ed software to work with these RAW format pictures before I can even see the images - and its gets complicated beyond this! I only have Photoshop CS2 and I am not a very competent user of the same either. Any advice on where should I be starting if I am looking at taking RAW format pictures - and more importantly - should I be doing it at all.

ken Rockwell (on his website) thinks otherwise! He is a strong believer i jpg format for he thinks that overworking on an image doesn't really make any discernable difference to the common human eye. What says you?


Best regards



Deepak Agarwal

[oxfordy]

Originally Posted by agarwaldvk

Hi Oxfordy

Thanks for your response.

One thing is now hopefully clarified in my mind without any doubt (I think) - that, as in my case, I am only changing (increasing) the dpi (without resampling, that is), as such, there is no need for sharpening.And since the original image from the camera was a jpg, some sharpening would have anyway been done in it anyhow! Got that!

Yes, that's roughly it. There's no need for sharpening *due to the resize*; there might be other reasons why you might want to sharpen though.

The output that I get from my D40 using the 18-200 mm AF...VR Nikkor lens in the jpg format is generally very good - I take it that, as you said in your post, there would already be some sharpening that would have been done by the camera itself, so I don't really need to worry about it.

Yes, almost certainly sharpened in camera. I don't know about the D40, but my D80 allows to specify the amount of sharpening applied to JPGs. You might want to look in the menu system for your options there. The only other problem with in-camera sharpening is that it is done before you get to edit the image. Some types of edit should ideally be done before sharpening (resampling is one).

I haven't tried taking RAW photos yet from my camera (I am assuming that it can) but want to - just to see what is the real benefit this format offers over jpg. I have cursorily read that I would need some spe******ed software to work with these RAW format pictures before I can even see the images - and its gets complicated beyond this! I only have Photoshop CS2 and I am not a very competent user of the same either. Any advice on where should I be starting if I am looking at taking RAW format pictures - and more importantly - should I be doing it at all.

ken Rockwell (on his website) thinks otherwise! He is a strong believer i jpg format for he thinks that overworking on an image doesn't really make any discernable difference to the common human eye. What says you?

Yes, Ken is notorious for his anti RAW sentiments! If you want your pictures to fall out of the camera in a "ready to go" state then Ken is probably right. If you get to the point where you want to be a little more adventurous with your editing, then RAW is the way to go. I use Nikon's Capture NX2 which makes working with RAW as easy as working with JPG and both much easier than Photoshop which I have never liked (bias declaration!). If you try editing JPGs too enthusiastically, you can wreck the highlights or the shadows really quickly, RAW gives you more latitude (though not infinite latitude!)

Hope that helps.

[OsmosisStudios]

No need to post full-res TIFFs. Just a 100% crop of parts, say 800x600?