** DPI and YOU ** -A POTN informational service-

amonline wrote:
I threw this together real fast; but it's the ins and outs of resolution, photography, dpp and photoshop in layman's terms. There is deeper information on the subject, but I wanted to keep this tackle simple.

Resolution for Dummies

Hope it helps...

Thank you sir Oh thank you so much, I actually understood the whole document Again thankyou sir

Franko515 wrote:
Thank you sir Oh thank you so much, I actually understood the whole document Again thankyou sir

You are most welcome. My goal was to keep things as simple as possible. There are too many people on this board trying to act like something they are not. I get sick of it at times. Simplicity is key.

Franko515 wrote:
Thanks so in review, I will forget about dpi and ppi and only worry about the crop (for a 5x7 the pixel dimension which I have listed needs to be divisable by 5 and 7, i.e. 2500 x 2100) In the event I need to change the dpi (if requested by printer) these number needs to be multiplied by 3 (if i wanted 300dpi) to get 1500 x 2100.

One more thing I crop my pic to taste, so after that should I put it in a program to change the pixel dimension. If so, what program could I use to convert them as a batch to say 5 x 7?

do I have this at least half right? Again sorry if these questions seem crazy, but this is all very new to me and I would like to have a clear understanding so I can help others if need be.

Thanks for all your help

Well you have to pay attention to the nubber of pixels, it's just the ppi figure you usually don't have to worry about. try and print a 25 x 35 pixel image 6x4 and it won't look so hot! dpi you can forget entirely.

You can't really batch convert to 5x7 as you lose part of your image, you have to choose which bit gets lost.

This may have been answered already i'm too tired to read the linked thread. Hopefully this makes sense.

Thanks for taking the time to answer my questions sir This is a great place to learn

Franko515 wrote:
Thanks for taking the time to answer my questions sir This is a great place to learn

No problem, people here taught me a lot so I help others. Hope it helps

This is one of the most confusing posts I've read with so many people who actually believe they are right and are way off the mark! Fortunately Tim is there to rescue all who stray

Here's a good links and my own explanation.

http://www.fotofinish.​com …ters/photo/reso​lution.htm

Here's how I see things.

What is important in all stages of image editing is the number and quality of the pixels you have.

Changing the size or resolution of an image with the resample box checked means you will be adding/subtracting information to/from the image. This will reduce the quality of that image as it's the software that is adding or subtracting the pixels and ultimately controlling the detail - although in most cases it does a pretty good job and you won't really see much difference unless you are trying to add/subtract a proportionately large number of pixels to an image - this can be true even with a high quality image.

If you have the check box empty however, you can change the print size of the image to any size you like but the number of total pixels will not change (the resolution will vary as you increase/decrease the print size). This can be important to retain maximum quality from your prints. You are keeping the same pixels but condensing them into a smaller area so the ppi has to increase...(same pixels, smaller area=more pixels per inch). Where by resampling in PS is adding/subtracting pixels to the over all image.

It's really a very simple relationship between the number of pixels(px) - print size (ps) (I'm assuming measurements are in inches) and the resolution (ppi).

px = ps x ppi

So it goes that

ppi = ps/px
&
ps = px/ppi

My 20D produces an image of 3504 x 2336 pixels. To retain the maximum detail I want to keep these pixels intact. I don't want photoshop adding new ones and I don't want it to be throwing away any either until I want to resize for the web or perhaps need to when printing.

When resizing for the web, generally I don't actually look at the actual size or resolution of the image. I want an image with a fixed number of pixels. Usually a maximum of 600 - 800 pixels on the longest axis. This gives a reasonable sized image on most screen resolutions.

Anyway I just enter a fixed number of pixels (say 600) on the longest axis - the other will change proportionately. This will give a pretty small image size but view at 100% and that's what you'll see on the web. You can use "save as" to save a jpeg or use "save for web" to get more control of the actual compression and size (in bytes).

Regards print size
When viewing your printed images you usually look pretty closely at a 6x4 or 7x5 print. You may view 10x8s slightly further away and you'll look at A3+ images say 19"x13" even further back. The maximum resolution a 20D image can print a 16x12 image is around 194 pixels per inch. I actually find anything above 180ppi this is fine for normal viewing distances of larger prints. Try it - Print one resampled to 300ppi and print one without resampling at around the 180ppi mark (no need to be too accurate with the ppi - just don't resample any print up to 19"x13". I regularly print larger images at 180ppi and don't see any difference.

I hope all this makes sense? Please ask if you have any further questions. I might nit be too great at explaining and if so let me know.

JD