<story><title>DIY True 4K Projector</title><url>https://youtu.be/YfvTjQ9MCwY</url></story><parent_chain><item><author>huhtenberg</author><text>Since the right people might be reading through the comments here -&lt;p&gt;I&amp;#x27;ve been looking at making a hi-res &lt;i&gt;ceiling&lt;/i&gt; projector for a living space. Perhaps not one, but a set of several projectors with an overlap, but the key point is that they need to be placed in a way so not to interfere with the normal flow of life. Nor to be easily shadowed by people walking around, etc. This (likely) mandates placing them around the room perimeter, possibly on the walls at some height. This in turn means that they will be projecting at an angle.&lt;p&gt;Do I understand correctly that it&amp;#x27;s not possible in principle to achieve proper focus on the target surface when projecting at an angle like this? That is if I am to project, say, a star field then it&amp;#x27;s not be possible to have stars close to the projector and far from it to be both in focus at the same time?</text></item></parent_chain><comment><author>Someone</author><text>In principle, it is possible. A tilt-shift camera can bring any plane in focus, so running it in reverse will project the image sharply on your ceiling.&lt;p&gt;See &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Tilt–shift_photography&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Tilt–shift_photography&lt;/a&gt; for cameras. &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;www.projectorcentral.com&amp;#x2F;Understanding-Lens-Offset-and-Lens-Shift.htm&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;www.projectorcentral.com&amp;#x2F;Understanding-Lens-Offset-a...&lt;/a&gt; learnt me that you can buy projectors that use this method. I suspect that back-projecting televisions (&lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Rear-projection_television&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Rear-projection_television&lt;/a&gt;) often use it, too.</text></comment>
<story><title>DIY True 4K Projector</title><url>https://youtu.be/YfvTjQ9MCwY</url></story><parent_chain><item><author>huhtenberg</author><text>Since the right people might be reading through the comments here -&lt;p&gt;I&amp;#x27;ve been looking at making a hi-res &lt;i&gt;ceiling&lt;/i&gt; projector for a living space. Perhaps not one, but a set of several projectors with an overlap, but the key point is that they need to be placed in a way so not to interfere with the normal flow of life. Nor to be easily shadowed by people walking around, etc. This (likely) mandates placing them around the room perimeter, possibly on the walls at some height. This in turn means that they will be projecting at an angle.&lt;p&gt;Do I understand correctly that it&amp;#x27;s not possible in principle to achieve proper focus on the target surface when projecting at an angle like this? That is if I am to project, say, a star field then it&amp;#x27;s not be possible to have stars close to the projector and far from it to be both in focus at the same time?</text></item></parent_chain><comment><author>lathiat</author><text>Look up &amp;quot;Short Throw Laser Projectors&amp;quot; it&amp;#x27;s somewhat possible with funky optics depending on how much distance you can afford.</text></comment>