d90, large, fine jpeg......resize

[bonosa]

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So if I resize a Large,Normal JPEG to 600 pixels, and a Large,Fine jpeg to 500 pixels so that the file size is about the same, am I gaining anything in having gone Fine? Or did I lose whatever advantage I had by resizing to 500? I can see how if both are 600, Fine will be better, but with 500 vs 600 pixels......????
thanks

 

[Hugowolf]

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So if I resize a Large,Normal JPEG to 600 pixels, and a Large,Fine
jpeg to 500 pixels so that the file size is about the same, am I
gaining anything in having gone Fine? Or did I lose whatever
advantage I had by resizing to 500? I can see how if both are 600,
Fine will be better, but with 500 vs 600 pixels......????
thanks

I don’t really see your point here, when do you envisage a situation when want to make this decision?

Either you want to reduce it to 500 or you want to reduce it to 600, how compressed it will be is a secondary decision. You still have the original, right?

Brian A

 

[bonosa]

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Well, I wanted to post the best quality I can on my bird forum and can't decide if 500 pixels of fine is superior to 600 pixels of normal.....(there's a max size of file allowed)

 

[sherwoodpete]

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Well, I wanted to post the best quality I can on my bird forum and
can't decide if 500 pixels of fine is superior to 600 pixels of
normal.....(there's a max size of file allowed)

I would go with the larger pixel size, and adjust the compression accordingly, to fit within the limits. This compression is adjusted when saving from the editing program.

It is not related to the original camera quality settings. You could start with the largest and best quality (or shoot in RAW mode).

Regards,
Peter

 

[Hugowolf]

Well, I wanted to post the best quality I can on my bird forum and
can't decide if 500 pixels of fine is superior to 600 pixels of
normal.....(there's a max size of file allowed)

Well 500 at fine will be better than 600 at normal, but can you, yourself, tell the difference in quality when you view the two side by side on your screen? If you difference is not noticeable, then the larger image will probably be better. For web viewing I generally post at an 8 or 9 compression level (PhotoShop levels). I don’t know what this translates to when compared to your ‘normal’ and ‘fine’. What software are you using to resize?

What size are others posting on that forum?

The image quality will also depend on what algorithms are used for the down rezing. PhotoShop has several choices, the bicubic ones generally producing better than the simple bilinear and nearest neighbor ones.

It might also be worth noting, that many people like to lightly resharpen after down sizing.

Brian A.

 

[bonosa]

--Thank you both.
the Fine and Normal are settings in the nikon.

I'm using Picasa and it just asks for the pixel size to resize to. I don't see a slider to set compression percentage. It does ask if you want min, regular or max quality.

I'll look into photoshop sometime. Most people on my forum post about 100Kb files.

 

[Hugowolf]

-- Most people on my forum post about
100Kb files.

But what pixel dimensions?

Brian A.

 

[bonosa]

-- Most people on my forum post about
100Kb files.

But what pixel dimensions?

Brian A.

Hmmm. I've had to educate myself since I last posted. I was getting confused why a 600 pixel Fine jpeg was about 200 kb and a 600 pixel Normal jpeg was 100 kb. I was thinking about bitmaps (bmps) where if there are 600 pixels, no matter what the quality of the image, the file size will be identical since it stores the data as pixel intensity per pixel. For jpegs blocks of 8 x 8 pixels are cosine tranformed and the coefficients are stored. So if I want 100% quality, I'll have to store 64 coefficients for each block. As I sacrifice quality, I store fewer coefficients and that reduces the file size. So that's why the jpeg size was variable depending on the quality, and on on the total number of pixels.

Regarding that particular forum, the only spec I was informed of was the file size should be around 100K.
Thanks so much for making me think

Now I should look into the nearest neighbor and bilinear algorithms you mentioned regarding resizing in Photoshop. I guess they are averaging the pixel intensities of neighbors in various ways.

 

[chuxter]

Thanks so much for making me think

The results can often be amazing.

Now I should look into the nearest neighbor and bilinear algorithms
you mentioned regarding resizing in Photoshop. I guess they are
averaging the pixel intensities of neighbors in various ways.

I suggest you start by understanding how the Bayer photosite data is demosaiced to render PIXELS. Then study what happens to pixel data when it is formated to a JPEG file. A good place to go to understand the latter is:

http://www.impulseadventure.com/photo/

Look around. Calvin has LOTS of technical articles about JPEG. He also has a free JPEG utility, "JPEGsnoop" that will show you the inside of your pix.

After all that, you can tackle the math involved in compression algorithms...perhaps. ;-)

--
Charlie Davis
Nikon 5700, Sony R1, Nikon D300
HomePage: http://www.1derful.info
'I'm from Texas. We have meat in our vegetables.' Trenton Doyle Hancock