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07/07/2005 07:03:15 AM · #1 |
I am somewhat new to the photoshop scene. I actually took classes on it, but they didn't explain the whys, only some of the how tos. I am trying to learn what I missed from library books and this forum. Both have been very eye opening. I need someone to clear this whole capturing dpi thing up for me. Apparently even at my highest setting (6M-tif format) my camera is capturing at 72 dpi or at least that's what it says when I open the image up in Photoshop 6. So in order to get a higher resolution, say 300 dpi , for printing, Am I always going to have to resample and degrade my image???? Can this be adjusted in camera?
What is the point in having a 6M camera if the resolution gets degraded before printing? Maybe I am making a mountain out of a mole hill, or I am misunderstanding this whole thing.
Question 2--Are there cameras that capture at higher resolution that cost between 500-800 dollars and what are some of them for when I start to upgrade? Does Canon have one? |
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07/07/2005 07:05:24 AM · #2 |
| Resolution is the number of pixels conatained in the image. If you go to Image Size in Photoshop take note of the pixel dimensions, up the dpi to 300 then retype the original pixel dimensions you'll note that the files size does not change. It's the physical print size that changes. |
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07/07/2005 07:07:58 AM · #3 |
| So are you saying that I am not really loosing anything in changing the resolution to 300 dpi? then what is all this about resampling adding pixels to my photos degrading the image, should I uncheck resampling when increasing resolution? |
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07/07/2005 07:13:18 AM · #4 |
| Resampling happens if you increase or decrease the number of pixels. If you change the image size to 300dpi but do not change anything else it will upsample your image (increase in size). Have a look what happens to the measure ments of your image when you change the settings. |
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07/07/2005 07:56:55 AM · #5 |
| I had to leave for a bit. Ok, I unchecked the resample box, changed the dpi to 300 and the pixels stayed at 2832w x 2128h (17.3M) and the image size went from approx. 39wx29h to 9wx7h. So is the best print I can hope for to be at 9x7 (or is this more like the equilvant to the size of the negative in film photography-or again, am I way off base?)? |
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07/07/2005 08:07:44 AM · #6 |
9 x 7 is the print size at 300 dpi.
You can get a very nice print at 200 dpi which is 10.5 by 13.5-- or you can enlarge in small increments without losing quality.
tutorial
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07/07/2005 08:09:11 AM · #7 |
You're not way off base. If you want every captured pixel to represent "one dot" on your printed output and want to print at 300 ppi (pixels per inch), then yes, 9x7 is the maximum. However, 150 ppi usually provides adequate detail for "average distance" viewing (i.e., not scrutinized up-close).
The DPI setting only matters when printing. You can set you image to 10 DPI or 1000 DPI in Photoshop and as long as you have the Resample checkbox disabled, all you are doing is changing a number -- you aren't affecting the pixels captured by your camera at all. |
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07/07/2005 12:09:59 PM · #8 |
| So, if I wanted a nice 16x20 print I could increase the dpi in increments and have a good quality print? How on earth do you get billboards from this--yes, I know, I am thinking big, but a guy I use to work with had the next up camera from mine and he had one of his photos on a billboard. |
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07/07/2005 12:19:21 PM · #9 |
| pixieland, you have a 3 megapixel camera, which is the same as my Olympus c-740. I have ordered 20x30 prints that looked fine. You will lose a bit of detail, and sure some cameras will make a better print that large, but you will not be unhappy. If you want to order a large print, go ahead. Well, as long as you are shooting at high resolution in your camera, utilizing all three megapixels. Good luck. |
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07/07/2005 12:21:23 PM · #10 |
Whether or not you can get a good quality 16x20 print depends on how far away it will be viewed from. Up close (i.e., held in your hand only a few inches from your face), the details in a 16x20 from your camera may look "soft". Hung on a wall, viewed from 3 meters away, it might look fabulous. Viewing distance is a critical factor in determining usability.
This is very true in the billboard case, which is meant to viewed from sometimes hundreds of meters away. Standing 2 meters away, it would probably look awful! Again, it is all about viewing distance. |
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07/07/2005 09:06:44 PM · #11 |
| Thanks everybody, I am feeling more comfortable with this now. I'm sure experimenting and ordering a couple of prints will further enlighten me. |
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07/07/2005 09:09:20 PM · #12 |
Isn't Photoshops default setting at 72 dpi? Which can be changed.
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07/08/2005 11:30:17 PM · #13 |
| Hey , that's what I first thought too. I don't know how to change it, I may need to look into this. I really need to find my camera manual to see what it says about this. I am going to be confused some more if it's just the default for Photoshop and my camera isn't capturing at 72 dpi. How's a person to know what they are really doing or seeing? If it's defaulting at 72 dpi, than what is happening when I change it to 300 dpi and how do I know what it really is and if I am interpolating/resampling for no good reason. Damn, square one. |
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07/08/2005 11:51:16 PM · #14 |
Originally posted by pixieland:
Hey , that's what I first thought too. I don't know how to change it, I may need to look into this. I really need to find my camera manual to see what it says about this. I am going to be confused some more if it's just the default for Photoshop and my camera isn't capturing at 72 dpi. How's a person to know what they are really doing or seeing? If it's defaulting at 72 dpi, than what is happening when I change it to 300 dpi and how do I know what it really is and if I am interpolating/resampling for no good reason. Damn, square one. |
Don't be confused. DPI is only relevant to print. Your camera captures a 2048 x 1536 or an interpolated 2832 x 2128. If you are displaying the image on a monitor the DPI is irrelevant. Changing the DPI without resampling doesn't change anything. It will still view the same size on your monitor. The only thing that will change is the print size. |
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07/12/2005 12:13:50 AM · #15 |
I guess I am mainly concern with submitting photos to stock. The stock photos are purchased for printing in many cases, so I wanted to be assured that I could produce photos with high enough resolution to be acceptable to sell as stock. Also in case a client wanted an very enlarge family photo.
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07/12/2005 01:23:41 AM · #16 |
Okay. You have an image. It is HxW in pixels. Let's just say your image is 100x100 pixels. (A pixel is a picture element, the smallest discernable part of your picture.) Now...as long as you don't resize your image, it's 100x100 pixels, period. Note that this is dimensionless, i.e. there is no size assigned to the pixel.
The image, in order to be seen, must be rendered. It can be rendered on a screen, or on a piece of paper (via a printer). In any case, the rendering device will map a pixel of the image into a pixel of the rendering device. The pixel of the rendering device has dimension...i.e. it has a definite size. We are assuming the pixels in this case are "square" and we are not adjusting the "size" (overall number of pixels) of the image when it's rendered. So we are mapping the pixels of the image on a one-to-one basis to the pixels of the rendering device. Our 100x100 image in will render at 100x100 pixels on the output device in this case. The size of the pixels will be determined solely by the rendering device since we are not altering the size of the image prior to rendering (we are not resizing).
So our dimensionless image is rendered, and the pixels acquire dimension as a result of the natural pixel size of the rendering device, be it printer or screen.
Now the rendering device renders pixels at a certain density. This density is usually denoted in Dots Per Inch (DPI). With screens, this density is not of any particular importance, simply because this value is not relevant. An image gets slapped on a screen, it gets zoomed, etc, etc, and people are generally happy with what gets presented.
For a printer, however, what gets printed is what you're stuck with. Generally, when an image gets printed, a particular size is desired. So if you want a picture that is five inches wide, and your printer prints at 300 DPI, then your picture will have to be 1500 pixels wide. If your picture is 3000 pixels wide, half of the pixels will have to be thrown out (resized) to achieve the desired size.
So the rule is, pixels / DPI = picture dimension (in inches).
If you set the DPI in an image, all you are doing is saying "This is the resolution of my rendering device." Having stated that DPI, it can now be seen how big the image will be when rendered at that resolution. Set the DPI (resolution) of the rendering device into the image software and you can see what size your image will be when rendered. If the size is not the desired size, resize your image so that the size is correct for the resolution of your rendering device.
So DPI does not affect your image one way or the other. It simply allows you to see what size the image will be rendered at that DPI (resolution).
DPI acts as a figure of merit based on the size of the rendered image. If a rendered image is 20 feet across, 1200 DPI would be absolute overkill. Likewise, 25 DPI wouldn't be all that great for an image that is rendered to six inches across.
There are rules of thumb for determining what DPI is required to achieve a particular "fineness" of an image. This is dependent in large part on the viewing distance. Most pictures are intended to be held by hand and viewed from a couple of feet away at most. So some resolution around 75-600 DPI is usually adequate for this type of viewing. If you are rendering a poster, designed to be looked at from several feet away, some other set of resolutions would be more appropriate.
Always look at what you are trying to achieve. In general, you might be looking for a 5x7 portrait for most of the images you are rendering...or perhaps a 3.5x3.5 or an 8x10. Since most of these types of images are viewed from about the same distance, they will all require about the same DPI to get the desired resolution. This means that an image ten inches on a side will need about double the pixels on a side that an image five inches on a side would need. In either case, the DPI would be about the same.
(Note that I said "on a side." Blowing up a 5x5 picture to 10x10 takes four times the number of pixels of the smaller image because we are talking about area, not length. Keep that in mind.)
If all this makes sense, then what you need to know is, "What DPI is appropriate for the image I want to render?" Well. That is outside the scope of this screed. Determining the correct DPI is left as an exercise to the reader.
Message edited by author 2005-07-12 12:15:51. |
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07/13/2005 12:03:28 AM · #17 |
LOL, take me by the hand , I am sorry I have been having a difficult time with this. Numbers aren't always my favorite things. I see that I need to set my resolution for the end result of how my image is to be viewed. And that screen viewing doesn't require as high a resolution as print viewing. And that I need to determine print viewing resolution based on the distance that the image will be finally viewed from(example-arms length or hanging on a wall) Am I on the right track so far?
You said, "if your printer prints at 300 dpi". How do I know what dpi my "rendering device" aka "printer" is capable of or for that matter anyone else's devices that I may be sending my images? I looked at my printers specs (My printer is a Canon S802 )and it says it's resolution is 2400x1200. Is this another equation I need to figure out to get the most out of my printer? If so, can someone please do the math for me, hold me by the hand and speak very very slowly. LOL, what if I say pretty please?
P.S. Am I the only one that's been in the dark about this stuff? Please one person post and tell me I haven't been alone and that you are trying to get an understanding like I have been by following this thread. |
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07/13/2005 12:38:34 AM · #18 |
As a rough guide, photographic images need not exceed 300 dpi at final print size, as described in the excellent summary posted previously.
Ink-jets don't really use pixel-for-pixel rendering. The reason they have such a fine dpi is that they use only four ink colors to render thousands of perceptible shades. To do that, each of the pixels in your photo is further subdivided (by the printer) into some combination of CMYK spots which will approximate the color of the original pixel.
If you have a 2400x1200 dpi printer, and a 300 dpi image, each of your photo's original pixels is broken into 8x4 or 32 drops of ink in whatever combination comes closest to the original color.
However, I always save my edited Photoshop file with the maximum number of pixels captured, and then make copies to be cropped and/or resized to the size I want to print |
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07/14/2005 11:10:16 PM · #19 |
| Thanks for all the input. Now I need to practise what I've learned. You guys are great as always. |
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