reduce jpg file size

Hello,

Can anyone assist? I have lots of photos (probably 1000) stored as .jpg files on my 2 computers, one of which is laptop windows vista Dell vostro, the other is desktop Iqon windows xp. My camera takes 10 mp photos so most file sizes are 5mb - 7mb. I discovered that if I open one of them with paint & then save it, it drastically reduces the file size, without affecting the quality of the display on the screen. Presumably if I actually printed them, or got a commercial firm to print them, then the larger file size would be better. But most of my photos are ok on the screen, without being printed out. It would take ages to open each one individually in Paint & then save as jpg, then delete the original. I could probably change the settings on the camera (at least I presume I can, never tried it yet; it's a Fuji). But is there any programme that lets me select multiple photos & reduce the file size (& quality) easily? Thank you. It would save me a lot of room, and I need the space at the moment.

I have used Total Video Converter on certain occasions when some jpeg files format have large file size. It can convert multiple pictures at the same time. However there are lots of free image converter that you may wanna try, http://www.nchsoftware.com/imageconverter/index.html
http://download.cnet.com/FormatFactory/3000-2194_4-10968547.html

If you can name the model number of the camera we should be able to help you find a setting to reduce the size of photos taken.
As for making them all smaller, in a batch, check out jhayz links as I have no idea about that =]

DM

Hi,

I usually use convert.exe, which is a command line utility, that's part of imagemagick to do this.
You can then use command line command to rename all files. Eg to rename all files in a given folder and copy the smaller files into a folder called smaller you can use this command:
for %a in (dir F:\photos\*.*) do convert -resize 30% %a %~dpasmaller\%~nxa
All files in F:\photos will then be processed by convert. It will resize the file to 30% of its original size (that's what the 30% means in the command line) and then copy the resulting smaller file into a subfolder smaller with the same name it originally had. The folder smaller has to exist before you start the resizing process.
Once you have checked the pics and identified that they are to your liking, you can then go ahead and delete all the big images.

This is a free solution, however, due to the lack of an interface and the need to use the command line, I realise this is not a solution for everyone.

regards myrti

Be careful when re-saving .jpg files.
.jpg is a lossy form of compression, and every time you re-save the same file, information gets discarded.
That's how you are able to make the file smaller.
With the loss of information, quality will suffer.

If you have no intention of ever printing these files, then the quality loss on 1 small re-compression (10%) won't be too noticable on the monitor.
If you decide to print (depending on the size of the print), you will notice a loss of quality in the image.
The larger the print, the more noticable the loss of quality.

If you need the room, I would keep the originals and burn them to disk, flash drive, or an external drive, then delete them from your computers.
I wouldn't compress them any further, to save space.

In your camera's menu, there should be some type of setting under Quality, that would reduce the file size of your images.
Just remember, the lower the quality, the smaller the acceptable print.

I would be very careful about downsizing quality on any images you value (per tg1911). The whole idea of jpeg and mpeg compression is to throw out information that is least interesting to the eye, namely colour. As time progresses, the quality of digital imagery has gone up hugely. Images suitable for 1024x768 VGA monitors 10 years ago look like crap today on say 1920x1080 monitors with DVI. Quality will follow the same direction exponentially over time. Also be aware that your eyesight and colour perception may not be as good as others when you decide how good your reduced images are. Ditto for the quality of your monitor!

Most basic image editors only give you the choice of quality as a % or number, usually 100% and 10 being the highest. However there are subformats for jpegs eg 1:1, 2:2, 4:2 etc. They come into play when you have high or low detail images. If you use a low quality or subformat such as 50% or 4:2, you will get artifacts like "mosquitoes" and pixelation. For images with sharp edges such as text or tree foliage, you need a high quality save % and subformat such as 95% and 1:1 to preserve the sharpness and reduce artifacts (also giving large file size). If you are using a basic editor, all you can do is go for a high quality %. Most basic editors seem to use a 2:2 subformat. As you cannot improve your existing images, they are presently at the best quality you can have. Any jpeg re-save will lose some quality.

My yardsticks for quality:
Desperate to save space but acceptable quality 82%, 2:2 subformat
General use for screen pics 88% quality, 2:2 subformat
Jpegs I may re-edit for screen 92% quality, 2:1 subformat
Valuable pics that are not .psd or .cpt or .bmp format, 95% quality, 1:1 subformat
Images being created and immediately edited/deleted but need to save space over bmp format, 98% quality, 1:1 format

The only software I have that allows you to set subformat and also read subformat off existing images is ThumbsPlus (payware). There are plenty of basic image editors. I use IrfanView as my PC default because it's small and quick. Picasa is popular. I also like FastStone Viewer which allows you to store thumbnails for quick referral. Most editors will do batches of pics.

All the above is not much help in resolving your problem! If I were you I would do as tg1911 suggested with the originals. You can bulk re-save the images at lower quality to another folder to use on your PC. In the future you can always refer to the originals if you need the best print or we get to 100 megapixel monitors.

Hi,

while I agree with you that compressing equals loosing information in this case, the user clearly states that he is aware of the data loss and that he has pictures taken with a 10Mp camera. I have a 5Mp camera and even those pics (that are only 2-3Mb tall) can easily be used for Din A4 and most often also for DinA3 prints. Depending on the camera, you may even go higher. If the thread opener is not intending to make life-sized wall posters out of his pictures, there is room for reducing the size without ultimately being affected by poor quality when it comes to printing or his screen.

This being said if you have 1000 pictures at 5-7Mb, this adds up to 5-7GB of data. You could simply buy a flash drive or a sd-card to store the pictures on (better buy 2 and use one of them as a backup ) and you'd have to invest maybe 20 bucks.

regards myrti

Hi Ricardo,

I have to agree with Myrti and your other respondents - keep your original images as your original images. My wife and I are involved in an on-line project which involves us taking lots of photos, we took something like 15,000 in two weeks in April, an absolute mininum of two images of each object. Once home I have the fun of picking the better image of each and titling it, sticking them on DVDs and shipping them off to my organiser and a friend in the same field, so I just make three copies of each DVD, one being for my file. Blank DVDs are cheap, I am getting mine from a local supplier for £GB 15 per 100, printable.

I was taught that once you throw resolution away, you cannot get it back. By all means, make low-res copies for use as wall papers and whatever, but keep your originals untouched. At some time in the future, you may want to go back to one of your original images. Yes, there is software for increasing the number of pixcels in an image, but if the information isn't there, this software cannot put it back in.

Oh yes, And don't keep your back-up copies beside your computer ! Being of a paranoid turn of mind, I normally keep my back-ups in our lock-up along with my wife's car. our wine and beer cellar, reserve coffee stocks and her bike. If the house goes on fire, we still have something to drink and a software back-up !

Chris Cosgrove

Thanks guys for all the useful information. My original photos are all stored on disk and flash. I only keep "working" files on the computer.I am compiling a catalogue (with many photos of rare plants which I grow) using MS Publisher 2010.I compared some file sizes and was surprised at the result. Looking at one Publisher document with only 5 photos & text, it is a big file = 5.62MB. When Saved As PDF set to "High quality printing" =239KB and then as PDF set to "Standard" = 131KB which is recommended for sending as email attachment. The printed quality of this page is very good for general correspondence. Now all this tells me that I have a lot to learn so any comments would be welcome please. What happens when you create a PDF?

Question: I was told that unless you need to print a photo, you only need to save it at 72dpi because that's the best resolution it can be displayed on a monitor.

Is this information incorrect?

I have four selling accounts on eBay, and photos are the best way I can increase sales. I use a lot of photos -- which takes up a lot of room on my hard drive and hosting domain. I host my own photos on my own domain.

Incidentally, I use Photoshop to crop but I use Irfanview's batch editor to resize photos and change resolution.

Thank you for any advice.

Re: Kate R

For digital images on PCs/Internet, dpi is not very relevant. The dimensions in pixels are. Having said that, the dpi may affect how fonts appear when you use Photoshop. In the old days, graphics apps may have worked with a default of 96dpi, many these days use 72. Those that work primarily for print may have their images set to 300dpi.

If you take a PC screen, say 1280x960, a 640x480 pic will take up 1/4 of the screen area regardless of what the dpi is. Dpi is only important when printing. The resolution of a digital image on the screen is solely a function of the number of pixels.

When the image is shown on a web page, other factors come into play. If the HTML code forces the image to be 320x240, you lose the original resolution because it scales the pic down. However, in a quirk of vision, crappy images reduced in size may appear nicer even though there is less detail. Also, the size of the image may also depend on the screen size and zoom factor the user has set in their browser.

If you use IrfanView to change resolution ie the dpi, it has no effect whatsoever on the image. A 640x480 image at 320dpi is the same size as a 640x480 image at 72dpi. 640x480! If you print them however, the first will be 2" wide and the second 6.7" wide. You can only change the resolution for a PC/Internet image by resizing. Upsizing may be detrimental to quality since pixelation starts to appear. Doubling the pixel dimensions for example means that every pixel in the original becomes 4 pixels of the same colour in the edited version. This should not be confused with taking a digital photograph where the more pixels there are the higher the resolution.

From the first question you asked, it sounds like you are trying to save HDD space by reducing dpi. That makes no difference. What makes a difference is if you have original pics say 3000x2000 that appear on the web page at a size of 300x200. It's best to keep your originals at the existing res for future use. In the example I quoted, I would make a copy of the the pic 300x200 for use on the site and store the original elsewhere (dvd, external HDD etc).

For digital images on PCs/Internet, dpi is not very relevant. The dimensions in pixels are. Having said that, the dpi may affect how fonts appear when you use Photoshop. In the old days, graphics apps may have worked with a default of 96dpi, many these days use 72. Those that work primarily for print may have their images set to 300dpi. When the image is shown on a web page, other factors come into play. If the HTML code forces the image to be 320x240, you lose the original resolution because it scales the pic down. However, in a quirk of vision, crappy images reduced in size may appear nicer even though there is less detail. Also, the size of the image may also depend on the screen size and zoom factor the user has set in their browser.

Thank you so much, Nanobyte! Wonderful information, and so simply explained, I think I've got the basics. I would like to sort of paraphrase a couple of points, however, just to make sure I'm on the right track, and I'd like to explain exactly what I'm looking for, as well.

First and foremost, photos make a HUGE difference on eBay. Here is a perfect illustration: Please compare this listing: http://www.ebay.com/itm/261099278887?ssPageName=STRK:MEBIDX:IT&_trksid=p3984.m1431.l2649
with this one: http://www.ebay.com/itm/110903085834 Both auctions sold/are selling the EXACT SAME TOP, but the first listing currently has a top bid of $13.49 -- that would be my bid -- the second listing sold for $79.99. That would be my auction. =)

Second point. eBay has been ramping up its efforts to entice buyers using smart phones and other mobile devices. "Last year alone, more than $5 billion was transacted via mobile on eBay, a figure we expect to double in 2012." Et cetera. I imagine it does wonders for impulse purchases. eBay's new marketing campaign will target this demographic. A sneak peak at the new TV ads: http://pages.ebay.com/sellerinformation/sellingresources/holidaymarketing2012.html

I'm partial to "eBay Bad Dog", myself.

To facilitate eBay listings on mobile devices, eBay now offers 11 free photos at the top of the auction page. These pix need to be 1600 pixels on the longest side. They need to be high quality, because the app allows buyers to zoom in. Please see this active listing for an example: http://www.ebay.com/itm/120988199989?ssPageName=STRK:MESELX:IT&_trksid=p3984.m1555.l2649

However, some people don't like this app, and prefer to see photos in the listing itself. Scroll down in the auction above, and you well see my (extremely basic) HTML listing that includes all the same photos, but notice that the longest side is fixed at 600 pixels.

I've been a reporter for a number of years (and an unemployed reporter for even longer), and regardless of column width, every print publication I've ever worked for requires art to be submitted at 300 dpi. I associated this with high quality images and for years, I entered ebay photos at 300 dpi. They were enormous, took up loads of space and took forever to upload.

Using the information you kindly provided, I took one photo (recognize the top?) and resized them differently, according to eBay standards, and my own, at 72 dpi and 300 dpi.

http://www.fozzybear.org/ebay/72dpi_1600.jpg

194KB
22.2 in x 17.4 in

http://www.fozzybear.org/ebay/300dpi_1600.jpg
638KB
8.4 in x 6.5

http://www.fozzybear.org/ebay/72dpi_600.jpg
195 KB
2.0 in x 1.6 in

http://www.fozzybear.org/ebay/300dpi_600.jpg
639KB
5.3 in x 4.2 in

If you take a PC screen, say 1280x960, a 640x480 pic will take up 1/4 of the screen area regardless of what the dpi is. Dpi is only important when printing. The resolution of a digital image on the screen is solely a function of the number of pixels. If you use IrfanView to change resolution ie the dpi, it has no effect whatsoever on the image. A 640x480 image at 320dpi is the same size as a 640x480 image at 72dpi. 640x480! If you print them however, the first will be 2" wide and the second 6.7" wide. You can only change the resolution for a PC/Internet image by resizing. Upsizing may be detrimental to quality since pixelation starts to appear. Doubling the pixel dimensions for example means that every pixel in the original becomes 4 pixels of the same colour in the edited version. This should not be confused with taking a digital photograph where the more pixels there are the higher the resolution.

This is the concept that flies so far over my head, I hear a sonic boom. The actual size of a photo is completely unimportant online, for some inexplicable reason, but regardless, I do get the fact that it just ~is~ this way, and I can memorize facts that I don't understand with the best of them.

Incidentally, those photos were all filtered with Noiseware Community Edition first.

Finally, my question is this: Will the naked eye, or eBay's Zoom app, result in a lower-quality photo if I use a lower dpi. I cannot see a difference, but I have a 15-inch diameter monitor.

From the first question you asked, it sounds like you are trying to save HDD space by reducing dpi. That makes no difference. What makes a difference is if you have original pics say 3000x2000 that appear on the web page at a size of 300x200. It's best to keep your originals at the existing res for future use. In the example I quoted, I would make a copy of the the pic 300x200 for use on the site and store the original elsewhere (dvd, external HDD etc).

I can put them on an external drive, but I don't really see why that's necessary. These aren't family photos, they're temporary photos that I hope never to have to use again.

THANK YOU SO MUCH NANOBYTE!!

Cheers,

Kate

The two eBay pages referred to look the same to me. I don't know what your point was there.

I've seen other catalogs with the facility to zoom in. Obviously they need to be large enough (in pixel terms) to have decent quality when zoomed fully in.

Re auction .....m1555.l2649, I see what you mean about the pics below. Those zoom pics don't always work. I have Firefox set up to minimize scripting etc so I had to switch to Chrome to view your page fully. So many sites such as eBay assume that everyone likes seeing Flash etc whereas if you are trying to sell to everyone, you should keep it simple. Adding the basic pics as you have done is a good idea IMO. The 600 pixel size may be an eBay limit. If those static pics were all you could post, there would be no point in having the pics any bigger than 600 pixels. However, if you want the zoom to work at its optimum, you may have no choice but to have the pics at 1600 pixel size (the 600 pixels versions are presumably are downsized by the webpage).

I don't know where you get your file sizes in kB from:
http://www.fozzybear.org/ebay/72dpi_1600.jpg and http://www.fozzybear.org/ebay/300dpi_1600.jpg are both 239kB
http://www.fozzybear.org/ebay/72dpi_600.jpg and http://www.fozzybear.org/ebay/300dpi_600.jpg are both 57.4kB
Save the pics off the webpage and look at their kB sizes in Explorer. It could be that eBay (or this forum) re-saves all images for posting at certain quality
All the pics are at a jpeg quality of 89%, subformat 2:2 which is a good compromise between size and quality.

"Will the naked eye, or eBay's Zoom app, result in a lower-quality photo if I use a lower dpi. I cannot see a difference, but I have a 15-inch diameter monitor." Nooooo! The dpi is completely irrelevant on a webpage. If you take the pics in the previous paragraph the _1600 pics appear identical size on the your PC screen because they are both 1600x1250 pixels. The _600 pics will appear much smaller on the screen because they are only 600x469 pixels. Having said that, if the webpage squeezed both pics down to 300x275, you probably could not tell the difference. If the pics were being zoomed on eBay, the _1600 pics would show more clear detail.

If you are absolutely sure you will never need the originals again then feel free to delete them. In such a case I would keep them around until the auction is over just in case you need to redo for some reason. That's up to you.

Your monitor size in inches is not a useful yardstick, your screen resolution is. Let's say for convenience the larger pic occupied the full width of the screen (ie your screen is 1600 pixels wide), then the smaller version would only occupy about 40% the width.

The two eBay pages referred to look the same to me. I don't know what your point was there.

Sorry about that -- the importance of using good photos on eBay is easy to see when you compare these two photos:

http://www.fozzybear.org/ebay/Mine.jpg
http://www.fozzybear.org/ebay/Other.jpg

BOTH AUCTIONS WERE FOR THE EXACT SAME SHIRT. Same designer, same style, yet "Mine" sold for $79.99USD and "Other" went for $13.49USD. It would have sold for less than that if I hadn't recognized it and bid on it myself. This is a vintage top by a popular designer that I will be able to resell for $50USD, at least, in a properly presented listing.

The 600 pixel size may be an eBay limit. If those static pics were all you could post, there would be no point in having the pics any bigger than 600 pixels. However, if you want the zoom to work at its optimum, you may have no choice but to have the pics at 1600 pixel size (the 600 pixels versions are presumably are downsized by the webpage).

I set my photos at 600 pixels because the photos are large enough to see details but it doesn't take forever to load the page. I write my own HTML for my auctions and host BOTH sizes of each photo on my domain, fozzybear.org. I store the 1600-pixel photos AND the 600-pixel photos because it's easier FOR ME to plug in actual numbers (i.e. "<IMG SRC="http://www.fozzybear.org/ebay/leo1.jpg" WIDTH="600" HEIGHT="353" alt="http://www.fozzybear.org/ebay/leo1.jpg">") than it is FOR ME to do a math calculation to scale down the 1600-pixel photos. Yes, this *is* a retarded system, I agree, but I am somewhat retarded when it comes to mathematics and I know from experience that I can avoid problems and save time by doing it this way.

I don't know where you get your file sizes in kB from:
http://www.fozzybear.org/ebay/72dpi_1600.jpg and http://www.fozzybear.org/ebay/300dpi_1600.jpg are both 239kB
http://www.fozzybear.org/ebay/72dpi_600.jpg and http://www.fozzybear.org/ebay/300dpi_600.jpg are both 57.4kB
Save the pics off the webpage and look at their kB sizes in Explorer. It could be that eBay (or this forum) re-saves all images for posting at certain quality

How odd. Also, all four photos are 96dpi. I set the resolution and size for those four photos in Photoshop, exactly as I described. Then I uploaded them to my domain, hosted by GoDaddy. Apparently, GoDaddy resets photo resolution to 96dpi, whether the photo is uploaded at 72 dpi or 300dpi. This is good to know -- I won't store any original-quality photographs I'd like to keep there.

All the pics are at a jpeg quality of 89%, subformat 2:2 which is a good compromise between size and quality.

Thank you! I'm happy to know I'm using a good compromise, but I wouldn't mind learning why this is so. It's not essential, but if you happen to know of a link or two to any tutorials written in layman's language, sort of a "Compression for Dummies" type of thing, I'd enjoy taking a look. If not, no worries!

"Will the naked eye, or eBay's Zoom app, result in a lower-quality photo if I use a lower dpi. I cannot see a difference, but I have a 15-inch diameter monitor." Nooooo! The dpi is completely irrelevant on a webpage. If you take the pics in the previous paragraph the _1600 pics appear identical size on the your PC screen because they are both 1600x1250 pixels. The _600 pics will appear much smaller on the screen because they are only 600x469 pixels. Having said that, if the webpage squeezed both pics down to 300x275, you probably could not tell the difference. If the pics were being zoomed on eBay, the _1600 pics would show more clear detail. Your monitor size in inches is not a useful yardstick, your screen resolution is. Let's say for convenience the larger pic occupied the full width of the screen (ie your screen is 1600 pixels wide), then the smaller version would only occupy about 40% the width.

So if you print a 300dpi photo, you get 300 pixels per inch -- very detailed. However, when viewing a photo on a computer monitor, there is ABSOLUTELY NOTHING I can do to improve photo quality, other than take a good photo to begin with. Is this correct? Or perhaps this is where "compression" factors in, which I don't understand and am really just satisfied to know I'm using a good enough one purely by accident.

What about LED monitors? Do images appear differently on those displays?

Thank you so much, again.

I don't know where to start!

If you use Photoshop and Irfanview primarily for web images, set the default units to pixels because that's what digital bitmaps use. Physical dimensions and dpi are meaningless. You may want to keep the dpi at typical values of 72 or 96 dpi. The heart of bitmaps are the pixels. Dpi (which is really pixels per inch) is merely a number that is in the file. If you paste the image into an application that uses inches or cms, or print out with no further manipulation, the PC knows what linear dimensions to use. Repeating, when it comes to what appears on your screen or the screen of someone viewing your webpage, the dpi is irrelevant. The only factor is the width and height in pixels.

There is very little difference in the the Mine and Other pics. Other is slightly larger and that's all. If you look closely, Other is actually poorer. Look around the lettering. There are "mosquitoes". These arise from jpeg compression. As I said before, often when you reduce size, the pic seems better. You are seeing less detail which in turn means you see less crap, in this case the mosquitoes. There's an optimum size because making it too small to read is not very useful!

I mentioned jpeg subformat which for these pics is 2:2. If you save in Photoshop at the highest quality the subformat is 1:1. This produces sharper edges but a much larger file kB. I think the jpeg save settings 7-12 in Photoshop are 1:1 and 6 and below are 2:2. Irfanview only saves at 2:2. They are fine for the Internet. I use 88% myself, trivial difference.

Re storing 1600 and 600 versions, you could easily get away with the 1600 alone but it's not a big deal having both. If you omit any pic dimensions, the webpage will show it at native size. If your HTML was:
<IMG SRC="http://www.fozzybear.org/ebay/leo1.jpg" alt="http://www.fozzybear.org/ebay/leo1.jpg">")
it would appear at its size which is 600x353 according to you
If you wanted to use the 1600 pic, and assuming it's in proportion and it's called leoBig.jpg, then you could use the code
<IMG SRC="http://www.fozzybear.org/ebay/leoBig.jpg" WIDTH="600" HEIGHT="353" alt="http://www.fozzybear.org/ebay/leoBig.jpg">")
and the large image will automatically be reduced to that size.
No biggie if you use separate pics.

The change in dpi of the pics that you linked to were changed exactly as I described. Many online services limit what can be posted so they may re-save at a given jpeg quality and a given dpi, and may resize the image too. In such cases, no point in going overboard with quality.

Re jpeg quality, I listed my preferences based on experience in an earlier post in this thread. A few years back people would save jpegs at awful quality because HDDs and webspace was limited. In these days of HD video, jpegs are trivial items and it's pointless saving at such low quality they look like crap. Jpeg compression works by throwing away information least noticeable to the human eye. You always lose quality and have to compromise between file size and what it looks like.

You are correct that the only way to improve image quality is to make a better picture in the first place. Given a certain camera, a 14 Megapixel photo is going to have a lot more detail than a 2 Megapixel photo of the same subject. Whether those are printed or on a PC screen, the 14 Megapixel will look better. The same applies to creations in Photoshop. The greater the image size in pixels, the higher resolution and the greater the size in kB. If the pictures are reduced to thumbnail size, there will be very little difference.

If you print at different resolutions the effects are similar to a PC screen. You mentioned printing at 300dpi. If you print the same image (same pixel dimensions) at 150 dpi, the image will be larger but will not seem as sharp and defects may be easier to see.