Aspect ratio determines the relationship between the width and the height of the photo/texture; 1:1 ratio means the width and the height of the photo are same, 2:1 means the width is twice big as the height and so on. First number always means how much the photo is wide.
One of the questions that bothers many of us is what is correct aspect ratio for photos we use in Second Life and why it is important to use the correct ratio? I think there is not just one correct ratio simply because different viewers use different ratios to display our photos so it actually depends of the viewer you use, and even more of where you want to put the photo? Its not same if you use it for profile or for pics section. And why its important to use the correct ratio? Because you want them to look nice and professional, and not like you had no idea what are you doing.
Textures –> Aspect ratios
Second Life Viewer 3.6
Search > Classifieds thumbnail – ~3:2 (101×69 pixels)
Search > Classifieds expanded – ~4:3 (159×120 pixels)
Search > Classifieds expanded > More Info – native aspect ratio
Search > Destination Guide thumbnail – ~3:2 (101×69 pixels)
Search > Destination Guide expanded – ~4:3 (159×120 pixels)
Search > People – 1:1 (100×100 pixels)
Search > Places expanded ~4:3 (159×120 pixels)
Place Profile – ~3:2 (290×197 pixels)
About Land > Options tab – ~4:3 (195×150 pixels)
Profile > Picture – native aspect ratio; thumbnail cropped to 72×72 pixels; zoomed uncropped up to 300×300 pixels
Profile > Real world picture – native aspect ratio; thumbnail cropped to 45×45 pixels; zoomed uncropped up to 300×300 pixels
Profile > Picks thumbnail – 4:3 (60×45 pixels)
Profile > Pick expanded – 4:3 (320×240 pixels)
1.x Series Viewers
(official Viewer up to 1.23.5, still used by some Third Party Viewers)
Search > All for “Classifieds”, “People”, and “Places” – 4:3 (256×192 pi×els)
Search > Places and Classified tabs – ~7:5 (398×282 pixels)
Search > Land tab – ~7:5 (358×252 pixels)
Profile > 2nd Life tab – ~4:3 (178×133 pixels)
Profile > Picks tab – 16:9 (288×162 pixels)
Profile > 1st Life tab – 1:1 (133×133 pixels)
Profile > Classifieds tab – ~3:2 (206×137 pixels)
Profile > Web tab – 1:1 (400×400 pixels)
A scrollbar uses 15 pixels on the right-hand side.
About Land > Options tab – ~3:2 (178×117 pixels)
Group Information > General tab’s “Group Insignia” – 1:1 (126×126 pixels)
For those who went wtf after reading these numbers I’ll try to make an example. Lets say you took a snapshot in SL, open the snapshot window and choose the “custom” size, while keeping the “Constrain proportions” option checked you set the width to 5100 and the height automatically goes to 2868 (for widescreen monitors), you save the snapshot on your drive. Then you do some editing and decide you don’t really need some stuff so you crop the photo. But you didn’t enter any numbers in the crop window, you just cropped it. At the end you save it and resize for SL, merge all layers and go to resize the image setting the width to 1024, your height automatically goes to 850. Then you open the viewer and upload the photo but somehow the avatar looks a bit fat? What happened? And when you put the photo in your profile it just looks bad… So you go back to the top of the post, check which viewer you have and where you need to put the photo. Firestorm, profile pics section. Ok, you need it to be 4:3 ratio, this means you need to go back to Photoshop and crop it again but this time you will set the width to 1024 and the height to 768. When you upload it in SL and open in the viewer it will look stretched but in the profile it will look perfect, same as when you edited it!
These aspect ratio numbers should be our general guidance when cropping the photos for upload to SL and deciding where to use it but I want to go into detail about resizing and cropping for the correct usage. The problem appears when we use the wrong ratio, for example the photo is cropped to 1:1 ratio and you need it for the “Pics” section in your in-world profile, or you don’t even count the ratio but just crop it randomly. Recently I visited a new shop from one of my photography clients, we agreed to make all vendor images in 4:3 ratio but her vendors on the walls were resized randomly which made most of the photos to look really bad and like I had no idea what I was doing.
The rule is simple; if the photos are going to be shown in 4:3 ratio (or any other, I just prefer this one because it fits in most places) your photo needs to be cropped with the same aspect ratio. If you are going to use the photo on a wide prim (for example 5 meters wide and 2 meters tall) then your photo/texture needs to be in this same ratio.
There is a great tool called aspect ratio calculator http://www.continuum2.com/js_ratio.php please bookmark this page and use it!
If you are not sure, its always a good thing to create a prim in SL with the same dimensions as the photo you need – for example if you need 4:3 ratio go in edit mode (Ctrl+3), create a new prim and select stretch, then click on the “Object” in the build menu window and look at the sizes section – x,y and z. It depends how you rotate the box but you only need 2 of them, in my case the green y was width so I typed 4 in the little window and blue z was the height and I typed 3 there and just hit enter. The prim is huge lol but in correct ratio so just click on one of the white dots and resize the whole prim to less giant size. Now if you apply your photo to this prim it should look same as it looks in PS, otherwise its wrong.
Here is a photo that shows some examples; first row shows 2 correctly displayed ratios and second row shows wrong ones. As you can see, if I apply an image with 1:1 ratio on a prim that is not correct square (its wider) the avatar will look fat – stretched and if I apply a wide photo on a perfectly square prim the avatar will look aquashed
Now when editing photos best is to start with the correct ratio, think where the photo will be used so you don’t have troubles later. Create a new file, enter the width and the height and then copy/paste your snapshot in that new file or simply drag it inside from the folder where you saved it.
One more thing we have to be aware of is that all viewers display textures using the powers of two – if my image is cropped to 1050×634 the viewer will resize it to 1024×512, if its saved as 1050×800 the viewer will resize it to 1024×1024 (and again you will see distorted image!). For all photos that will be used inside Second Life, it would be good to set the width and the height to one of these sizes: 8, 16, 32, 64, 128, 256, 512, and 1024. If not the viewer will resize it anyway to the closest number. Of course LL had to make it harder for us so the photos we use in profiles are not shown using the powers of two but its still important because you want to keep the quality of the image so the less resizing the viewer does, the better for us.