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Old Feb 26, 2003, 5:03 PM   #1
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Hi, I am new to this board and couldnt think of any one else to ask, I appoligize if this has been asked/answered a milliion times, i couldnt find it.

I have a Olympus D-620L, it is a few years old but appears to take great photos. The question is regarding the settings, I have 3 choices, SQ,HQ,SHQ, I have used all 3 and found the SQ to be a smaller low quality pic. However, the other 2 seem to produce the exact same size picture, 1280x1024 or something. The only difference is the kb of the file, while HQ is about 150-250kb the SHQ are about 700-1000kb, what am I missing, they are the same size and resolution, according to my computer, only one is a much bigger file.

Sorry for being so long, anyone who can shed some light on the subject would be much appreciated.

Thanks
C
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Old Feb 26, 2003, 5:12 PM   #2
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HQ uses more compression than SHQ.



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Old Feb 26, 2003, 5:17 PM   #3
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OK, but, what does that mean to the pictures I take?? will they print better in one than the other, can I make one bigger than the other, I dont understand why I should use the SHQ other than to fill up the card faster. I get 144ppi using both modes.

Thanks for your responce, any more info will be helpful.

C
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Old Feb 26, 2003, 6:32 PM   #4
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Hi Carmen

Welcome aboard to this forum.

Thick of compression as "sampling" of the boxes
(ie, the rows and columns of differing colors) that make
up your picture.

Imagine you take your photo in SHQ.

This probably means that 1/4 of the boxes are
sampled, ie saved.

1/8 of boxes are sampled/saved for HQ.

1/16 of boxes are sampled/saved for SQ.

These boxes are "assembled" digitally to create
your files.

If you can take the same photo in SQ, HQ and SHQ.

Then zoom in on the photos after you download them.

You will see the stairstep effect appear much soon in
in the SQ than you will the SHQ.

Hope this helps

Somewhere else on this forum, compression is explained but I did not have time to search for it.
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Old Feb 26, 2003, 9:22 PM   #5
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Quote:
Originally Posted by Carman69
OK, but, what does that mean to the pictures I take?? will they print better in one than the other, can I make one bigger than the other, I dont understand why I should use the SHQ other than to fill up the card faster. I get 144ppi using both modes.
ppi is meaningless as a measure of the picture quality. 144 is an entirely arbitrary number. It is the total number of pixels and the "quality" of those pixels that matter. More JPEG compression decreases the "quality" of the pixels.

Use your photo editor to magnify the images until they are something like 200pixels showing across your screen. With the highest compression (smallest file size), you should see "blockiness" of 8x8 pixels -in sky areas in particular. That is JPEG compression. It is more subtle with less compression, but still there.

The JPEG compression will also show up near high contrast edges, e.g., a roof-line against the sky.

The more compression (smaller file size) you have, the larger those effects will be. It may well be hard to see - but you will notice it if you ever try to do detailed editing.
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Old Feb 27, 2003, 1:50 PM   #6
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Thanks very much you guys. I now understand what the different file types mean, so if I do no editing to the pictures and just want to print them, will I see a difference between the SHQ and HQ. Providing I print at the sixe the picture is taken. or even smaller like 5x7 or 4x6. I was told thats where ppi makes a difference, however, i cant see it on my monitor. If I up both pics to 200 or 266 to get a better resolution will they both look the same.

Thanks again, you have been a great help.

C
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Old Feb 27, 2003, 2:48 PM   #7
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Carman69

You will see no difference between the HQ and SHQ when printing at 5X7 or 4X6. The SQ would be fine for posting items on a web site because it has a smaller footprint.
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Old Feb 27, 2003, 3:03 PM   #8
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Quote:
Originally Posted by Carman69
Thanks very much you guys. I now understand what the different file types mean, so if I do no editing to the pictures and just want to print them, will I see a difference between the SHQ and HQ. Providing I print at the sixe the picture is taken. or even smaller like 5x7 or 4x6. I was told thats where ppi makes a difference, however, i cant see it on my monitor. If I up both pics to 200 or 266 to get a better resolution will they both look the same.

Thanks again, you have been a great help.

C
Correct me if I'm wrong fellas,

...but, PPI applies to printing and/or film scanning only. If you take a HQ photo and print it on a 300ppi and a 600ppi printer, you'll notice that the 300ppi photo will be of less detail...regardless of what you are printing (and what compression your images are in).

On the other side of the coin, if you print both a HQ and a SHQ photo on a 600ppi printer, the HQ photo will be of less quality.

I could be wrong of course.



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Old Feb 27, 2003, 4:59 PM   #9
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The thing about compression is it only really shows its defects when you're shooting lots of detail and possibly want bigger prints. You can't see the defects on the lcd. So if you want to avoid a mindset of analysing your scenes as a JPEG compressor, knowing what bits are difficult and what bits aren't, shoot the biggest file you can afford memory for and with acceptable write delay.

Your example of FIXED resolution printing can give consistent/predictable sharpness estimates for print sizes and the same is true of cam Mpix. But compression distortion depends on the type of detail and how much there is in the scene. It's not a linear thing like twice this gives half something else. In fact it has a cliff edge where you don't notice much wrong until some or all of a type of detail occurs and the fixed amount of compression the cam applies then becomes too much for that scene.

Also, it can occur in those parts of a scene with flat smooth colour like sky - so can be more obvious to some. 'Some' is important. The clever chaps that developed the compression system exploited the weaknesses in our vision to hide or mask the distortions, so blowing up with an editor is a bit unfair. Unfortunately, once you know what these artefacts ar, you become sensitised, more critical and learn to hate them.

With compression you don't get the gain of smaller files, lower card sizes and cost without some pain - and that's distortion which can make a difference with big prints and doing silly things like keep saving compressed versions over several editing sessions - the distortions just keep adding up on your pics!

Welcome to the digital world!
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Old Feb 27, 2003, 5:56 PM   #10
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OK, so just to make sure I understand this correctly. If I shoot in either HQ or SHQ, and print a 5x7 from a true photo shop, I will get the same quality photo? If thats right, under what situation would I need to shoot SHQ, only if I am edititing or blowing up? I was told I couldnt get much bigger than 5x7 from a 1.4MP camera.

Sorry, I appreciate all the help, however some of the responces are a little technical for me. I really want to know, weather or when i would want to shoot in SHQ. All it does is fill up my card faster. Most of the stuff I do with the pics is on the computer or web, however I would like to have some printed copies. I have tried printing on my inkjet with poor results, it is however a crap printer. Lexmark Z22.

Thanks again sooo much it has been quite helpful.

C
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