Our website uses what is known as "responsive design", and will scale images which are wider than your browser window to fit on-screen. This means that if your browser window is not wider than about 1850 pixels (allowing for page margins and scroll-bar), you will not see a full-size image which is 1800 pixels wide; it will be scaled to fit your page width. The screen/browser resolution data that we have available indicates that about 2/3 of our members are using screens with HD (1920 x 1080) or higher resolution, and will be able to see 1800 pixel wide images with no scaling. People viewing the site with tablets or mobile devices will fall into this category. This responsive scaling also means that you will never have to scroll horizontally to see the full width of an image. This is the reason why you rarely see a horizontal scroll-bar on our website - it will only be present on a few table-layout pages.
If your browser window is wide enough to display the image at full size, there will be no scaling; this means that an image which is 1800 pixels high will need a browser window about 1950 pixels high to see the whole image which is 1800 pixels high (allowing for browser title/menu/address bars and task bar at bottom of screen). Very few of our members have screens with such high resolution; to see the whole of an 1800-high image they will need to reduce their browser window width - yes, it sounds counter-intuitive - to cause the image to be scaled until its height is reduced sufficiently to display in the browser window. For example, there is an image in the Advanced competition which is 1350 wide x 1800 high; on my desktop monitor (1680 x 1050 resolution), with a maximized browser window, I can see the image at full size, but I only see about half of the image height; I need to reduce my browser window width to about 750 pixels to see the complete image, which at that point has been scaled to about 50% of its full size. I would do this if I was assessing images for voting, so that I could see the overall composition; I would also view it full size to see image detail.
I plan to publish this information on the site soon, so that people with screens which cannot display an 1800 x 1800 image at full size will know how to get the "best of both worlds" with the large image format.
Rob
BirdLife Photography Website Administrator