When you take a high res screenshot of an object in orthographic view in unlit env, the object size in pixel is the same no matter the resolution multiplier. For instance if you set it to 10.0 the object will be very small in a huge image.
I was able to verify what you are reporting and went ahead and entered a bug report for the issue UE-16532. If you have any questions or need additional assistance please let us know. Thank you for taking the time to enter a bug report for this issue.
Simple workaround: set screenshot region as a part of needed region.
I saw that this issue has been marked for “Won’t Fix” due to time and would like to reopen the issue. In version 4.17.2 the High Resolution Screenshot tool still doesn’t work for any orthographic viewport. Reproduction steps are the same as before, with the exception that this happens in all viewmodes, not just unlit. Selecting a region instead of capturing the full screen seems to have the same issue.
I would like to use these steps to create high resolution top-down images of my environments, but so far have had to resort to using Immersive Mode to maximize my screenspace (even going as far as hiding the Windows taskbar!) and taking a good old-fashioned screenshot that way.
I would also like to request that if this issue is looked into, can we also add a way to easily lock all LOD’s to their highest quality when taking a screenshot? It doesn’t take long before the landscape morphs and eats up all of my meshes, and it would be convenient to have a quick toggle available.