Very basic question about resizing photo for uploading


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pop

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#1
In order to upload to the gallery, we have to keep the photo under 100k. What is the best way to do this?

I used photoshop with a few of my photos. Mine is a 6MP cam, so the photo comes to about 2.7MB each or thereabout. However, I am very puzzled why, after resizing, the size vary so substantially, when I perform the same steps for each photo.

First I reduce the size to about 20% height & width, then I save to a jpeg file using quality 8. Despite the photos all having about the same size initially, the resized photos can very between 50k to 200k plus. As a result for those above 100k, I have to further reduce the size and save at a lower quality.

Please tell me there is a better way to resize photos for uploading. Thanks.
 

pop

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#3
Isaiahfortythirtyone said:
resize to 800x600
save at quality 7-8 in PS
no leh, I just tried this on one pic, the result is a file of 261KB.
 

pop

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raptor84 said:
resize to about 800x533 or 750x500 then use the save for web button. You can move the detail slider till it drops below 100 :)
thanks, got it now. you meant adjusting the quality till the size goes under 100k right? But what does the quality mean here? Meaning the picture gets worse and worse? In order to fit into 100k, my pic has to save at under 30% quality now.
 

pop

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raptor84 said:
Yes there will be more compression aritfacts. You cna select the 2up view to compare the orginal and modified versions.
thks, appreciate! :)
 

soma

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#8
pop said:
thanks, got it now. you meant adjusting the quality till the size goes under 100k right? But what does the quality mean here? Meaning the picture gets worse and worse? In order to fit into 100k, my pic has to save at under 30% quality now.
Try to save it as high in jepg not gif the size should go near 100k or if slight more just change the 800 to 700 in the below size change.
 

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#11
I use dimin viewer n5 to do batch resizing for uploading. It's free, it can do batch resizing and renaming, supports EXIF and many formats including digital camera raw. Just set your jpeg compression factor and resize all your files effortlessly.
 

Stoned

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#12
saving for web usually results in images that are under 100kb, even for images with a lot of detail. the main reason why saving as normal jpeg takes up so much space is that exif data is saved along with the image.

Why do images vary in size? it depends on how much detail there is in a photo. A shot of a busy street for instance, would take up much more space than a shot of a blank wall.
 

#13
Don't know if IRFAN view can solve your problem. But generally, genuine fractals like irfan view do reduce size, change dpi, etc. To keep the quality and sharpness, keep 150 dpi, and sharpen before you save. Otherwise the photos look a little soft.

Good luck.
 

LogicA

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try saving under GIF, can result in very small file size :)
 

Apr 12, 2005
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The size of the file depends not only on the compression used and the picture's resolution (how many pixels) but also on the uniformity and parterns of what is captured. For e.g. if there is a patch of the same colour of about the size of 20 x 30 continguous pixels in the picture, the compression may just use much fewer data to represent this patch by specifying its exact location area in a certain way together with just one colour code. In contrast, in a totally uncompressed format, each set of data represents only 1 pixel.

Try this to confirm : open a picture in your photoshop and then use paint bucket to pour the whole frame as complete white or complete black and then save it as another name with the same jpeg quality. A 427x640 350KB original picture now turned completely black will be just 35-40KB in file size even though the resolution remains at 427x640 and it has been saved in the same picture quality.

You may want to try using Windows Paint to open and then save the picture into smaller file size as the Windows Paint uses a lower bit rate (i.e. more limited range of colours in its palette) to represent the colours. The loss of colour and picture quality seems to be acceptable although it may not appear as vibrant under scrutiny. A 427x640 350KB picture may be only 70KB in size after using Windows Paint to save it. Remember to save as another name in order not to over-write your original better quality picture.
 

Apr 12, 2005
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#17
photonick2004 said:
Don't know if IRFAN view can solve your problem. But generally, genuine fractals like irfan view do reduce size, change dpi, etc. To keep the quality and sharpness, keep 150 dpi, and sharpen before you save. Otherwise the photos look a little soft.

Good luck.
The DPI specified in the picture is just a data in the file and has no major baring on the file size. It's only used to determine the actual printing photo size in inches when your home/consumer printer prints it.
 

Apr 12, 2005
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#18
LogicA said:
try saving under GIF, can result in very small file size :)
There is too much deterioration in quality if it's compressed into GIF.
 

Apr 12, 2005
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#19
Stoned said:
saving for web usually results in images that are under 100kb, even for images with a lot of detail. the main reason why saving as normal jpeg takes up so much space is that exif data is saved along with the image.

Why do images vary in size? it depends on how much detail there is in a photo. A shot of a busy street for instance, would take up much more space than a shot of a blank wall.
Yes, can use photoshop's "save for web" which is similar to Windows Paint.

Quality is still acceptable as long as the quality is not too far below 50% in the quality setting.
 

solarii

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#20
Clockunder said:
There is too much deterioration in quality if it's compressed into GIF.
Agreed. GIF is for graphics, not photos.

You could resize in photoshop by resampling to around 22% of its original size, sharpen with USM then save with a quality of 8.

Upload to photobucket and link here. Should give you nice sharp images to display.
 

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