![]() And besides, as already pointed out, it's the confusion between pixel size and file size on disk that is the most common problem. But I am aware that a lot of people are afraid of maths and I think that those who find it difficult to understand the Alamy guidance will probably find your equations very daunting. I did maths to degree level back in the 70s and I've been into digital imaging since the 90s. Just substiture your own cameras file sizes where I have put mine and you However if you need to crop an image it is better if you know what the limits are and you won't know that without doing the maths. I was also concerned a little about even whether to post this and whether I would be teaching my grandmother to suck eggs. To then increase the height by a relative amount, you will need to do the following equation. When resizing relative to the aspect ratio, you will set an amount for one side of the image. Image size is called pixel size by Adobe and in the general literature.ĭon't be afraid of the equations, they are made more scary because of the big numbers. In order to calculate the aspect ratio of an image, you will simply need to divide the width by the height of the image. I think the main problem over time has been the confusion between file size and image size (as JohnB has posted while I type). I hope this helps those struggling to work out file sizes.įorgive my skepticism but I think that those who struggle to understand file size requirements are going to blow brain fuses looking at your equations. Please remember that when you convert your images to JPEG the file sizes will be much smaller than this. If you do not keep the same aspect ratio then you will need to put what data you do have into the basic formula and transpose for the unknown dimension. Should Alamy change the 17MB minimum file size just substitute the new size in the basic formula at the start of this post. If you keep the same aspect ratio for your crop then you only need one of the dimensions if you crop is Photoshop as there is a preset for this. Substitute this back into equation 1 above to get the minimum width: _ = 17, then cross multiplying this becomes:Īy 2 = 3977656 so the minimum height for a cropped image from my D200 would be: Where does this get us? If we substitute this for the width in the basic formula at the start of the post we can find the minimum height for the cropped image: For images with the same aspect ratio we use the properties of similar triangles:Īx / AD = Ay / CD where Ax and Ay are the cropped width and cropped height sizes, respectively. The slightly trickier part comes in if you need to crop the image. _ = 28.71MB in size, well over the current minimum of 17MB So for my Nikon D200 an uncropped image saved as an 8bit TIFF would be: The 1024 x 1024 comes from the fact that each pixel of information is stored in a byte of data and there are 1024 bytes in a kilobyte (KB) and 1024 KB in a MB ( File width (pixels) x File height (pixels) x 3 (for the three channels, red, green and blue) ) I'll start with the basic formula for full size images then move on to show how to work out for cropped images. Even buses pass us on a set ratio.This has been brought up several times so I thought I'd try and show the maths behind it and how it can be changed to recalculate new sizes, should Alamy change the minimum size requirement. Ratios are everywhere in our lives, from the amount of vergetables and fruit we eat per day to the split of calcories we consume in general. ![]() Calculations can be saved to a table by clicking the "Add to table" button, the table appears the first time the button is clicked).Diagonal: Distance from top of one end to the bottom of the opposite end of the rectangle.Aspect Ratio (n:1 format): Aspect Ratio as a number against 1.Aspect Ratio (w:h format): Aspect Ratio of width against height.1.33:1) About the Aspect Ratio of a Rectangle Calculator 4:3) or as the width value against 1 (e.g. Aspect Ratio is the ratio of the width against the height of a rectangle, this is expressed as either the simplest values (e.g.
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