You may have had some clients request that the photos you took of their property be delivered at 300 DPI, or with a resolution of 300 DPI, and wonder how you do that.
The good news is that your photos probably already satisfy this requirement. Here's what it means, and how you can make sure you're providing images at 300 DPI.
DPI stands for 'dots per inch', and is often used interchangeably with PPI (or 'pixels per inch'). DPI or PPI are concepts that are used for printing and only relevant in that context.
So, when you clients ask for 300 DPI, they are likely just wanting to make sure the images you provide are large enough for them to include in brochures for the property listing.
Given the high resolution of modern cameras, however, your images will always be big enough for the client's printing needs. They will also be big enough to upload to MLS (Multiple Listing Service).
You will just need to make sure you keep the images at their original size through the editing process and deliver the full size image.
Now that we've covered the basics, let’s dive a little deeper into what DPI is, how it is used for printing, and how to make sure your image is the correct size for the desired prints.
The original term of 'dots per inch' when referring to a digital image was coined when the image was printed using a 1 to 1 ratio where 1 pixel was equal to 1 printer dot. While printing has changed a bit since then, in this context a 'dot' is basically thought of as just a pixel.
You have probably noticed that many photography applications offer a setting to change the DPI. For digital images not being printed, there is no need to change it.
In fact, it is often better not to, because some software will allow you to resize the image along with the DPI, which can end in very poor quality, pixelated images. While the DPI doesn't affect the image if the pixel dimensions remain the same, changing the dimensions when you change the DPI will of course change the size of the image.
To give an example of a specific need a client might have, let's calculate the pixel size you would need to deliver for a 300 DPI image that can be printed at 8x10".
This math is very simple: just multiply the dimensions by 300. To meet this request, you will need an image that is at least 2400x3000 pixels (or 3000x2400 depending on the orientation of your photo).
You can use this same method to calculate the size for any other print size they might need, and it is always ok to have the image be larger than what’s required. Some image editors show you the size and DPI of images. For example in Photoshop, you can see it by selecting 'Image > Image Size' from the menu while an image is loaded.
If the photo isn’t being printed yet you are still being asked for a 300 DPI image, this is likely because of a misunderstanding about what DPI means. It is a common misconception that an image must be 300 DPI to be 'high resolution', and many people just want the highest quality image possible.
In this situation, what they really want is almost certainly the image at it’s full size, saved in a high quality way.
If you don't resize the image at all beyond any required cropping for straightening or aligning bracketed shots, this should suffice for anything they might need as far as pixel resolution goes.
To save the image without losing a lot of quality, there are a couple of options. TIFF files are lossless and provide the best quality, though they are rather large files.
JPEG is a lossy format, but if you save with a higher quality setting, the loss is pretty negligible and the file size will be much smaller.
If your client has requested a 300 DPI photo and you send a full size TIFF file or high quality JPEG, they will more than likely be satisfied.
Photomatix wants to keep things as simple as possible for you, so it does default to 300 DPI on output settings. Odds are very good that you won't ever need to worry about the image size when you're working with full resolution images!
To learn more about image editing for real estate photography, check our learning center.