Q: What is an HDRI?
A: Hdri (High Dynamic Range Image) is an image that has a much higher dynamic range than is displayed in image that was shot using a single exposure. Low dynamic range images are usually contain pixels using 8 bits per channel with values ranging from 0 to 255. In comparison HDR images are floating point and have pixels with values ranging from 1 to 1000,000. This is achieved by shooting a range of exposures from very low to very high, these are then combined to make an HDRI. For the purposes of CGI The HDRI must show the full 360 degrees of an environment.
Q: Why do I need to use HDRI’s?
A: If highly photorealistic results are required then the fastest approach is to use IBL (image based lighting). This is where an image of a full 360 degree environment is imported into a renderer which then uses the image to light a scene as apposed to a more traditional approach where 3d lights are used. If CG (computer generated) elements need to be integrated into a live action plate then an HDRI that is shot at the same time as the back plates will make this very easy to achieve.
Q: Why can’t I just use a low dynamic range image to light my scene?
A: As explained in question 1 an HDRI has much more range in it than a LDRI. If you were to use an LDRI to light a scene it will appear very washed out and flat. To understand this, imagine a scene with a figure wearing a white shirt stood in the middle of a field, the sky is blue, and there is a bright sun. If this image had a LDR and you were to sample the range, the man’s shirt would have the same value as the sun because the maximum value of this type of image is 255. This means that the lighting will produce very flat results because the the overall value/range in the image is very similar. If this image has a HDR, the value of the shirt would still be around 255, but the sun would have a much higher value. The renderer will then create a much higher intensity of light coming from the pixels in the area of the sun and a much lower intensity in the area of the shirt. Therefore we have a lighting solution that works as it would in the real world.
Q: Why are the HDRI’s at such a high resolution?
A: This is to make sure that there is enough resolution in the rendered reflection. If you wish you can reduce the size of the HDRI in Adobe Photoshop or equivalent software.
Q: The backplates look very washed out when I render them in my scene, why?
A: The back plates are srgb with a gamma of 2.2 so if you a rendering using linear colour space this will make the images appear very washed out. To compensate for this you must apply a gamma correction of 0.4545, the images will then render correctly in your scene.
Q: Can I use these HDRI’s in any renderer?
A: Yes, you can use the HDRI’s in any software that supports IBL (image based lighting).
Q: I have created an account with hdrishop and have bought some packs. When I log into my account I can see all of my purchases, will the ability to download these expire?
A: Your packs will always be visible in your account but there is a limit of 5 separate downloads on each pack. If you exhaust this limit and need to retrieve your purchases just drop us an email and we will forward them to you.
Q: Are the HDRI’s royalty free?
A: Any images you purchase are royalty free. For further details please refer to our legal page.
Q: Are the free samples Royalty free?
A: Any free samples are royalty free. For further details please refer to our legal page.
Q: Once I’ve purchased an HDRI can I return it?
A: No, just like all other digital content, once you have purchased any images or packs you can’t return them.
Q: What file format do the HDRI’s and back plates come in?
A: The HDRI’s are in exr format and the accompanying back plates are in tiff format.
Q: I have downloaded my purchase but when I open the folder there is only one file inside.
A: All purchased are compressed into one file to reduce the size to speed up download, simply uncompress using any of the most common compression software such as winzip, winrar, 7zip or equivalent on mac.
Q: I’m having trouble getting my HDRI’s to work correctly, what can I do?
A: You can refer to our tutorials area for guidance on simple setup for Modo and Vray. We also have a forum area where you can post work in progress or have any questions. You can also contact us directly through our contact form and leave us a message. we endeavour to answer all messages within 24hrs.
Q: Can I submit images for consideration for the Hdrishop gallery?
A: The easiest way to do this to post your work on the Artwork section of our forum.