This article was written prior to the current formulation of the ObscuraFlex focusing screen, while the basic information remains the same, the new screen has still finer texture and more even image diffusion characteristics.
Nonetheless, may notice a "grainy texture" on some photos. Here’s what you’re probably running into…
At full res an iPhone 15 Pro or similar is capable of 48-Megapixels, or 8064 pixels across, which (when looking at a 4"x5" screen means it’s seeing detail down to 1/1600th of an inch or about 15 microns, a level of detail five times smaller than a human hair, or about 8 pixels for the smallest spec of dust the naked eye can see. It’s like scanning a 4x5 film negative at 1600 dpi. You will definitely see grain. You will definitely see dust.
Above is a comparison that illustrates the issue. From right to left I have blown up a one inch tall section of an image from; ObscuraFlex using a traditional 4x5 fresnel screen, ObscuraFlex using a high-end fresnel screen, a film negative, and ObscuraFlex using an ObscuraFlex focusing screen. *Click the image to see it in full resolution.
If the far right image is not the level of clarity you are seeing from your ObscuraFlex™ screen, please reach out to discuss the issue via the contact page. I will answer.
The iPhone 16 Pro especially appears to actually ENHANCE the texture of the screen, an effect I'm investigating but believe is a result of software sharpening.
You can experiment in a few ways to mitigate this and see what works for your style:
- by focusing the phone slightly beyond the surface of the screen, using an app with manual focus and drift your focus number up or down a fraction to focus on different layers of the diffusion screen.
- by shooting at a higher ASA setting. When shooting at 1000asa or higher, the image sensor produces more noise/grain of its own, this can help to mask any texture the lens is seeing on the surface of the screen.
- by locking focus on a part of the screen that’s not dead center. Because of how close the screen is to the phone's lens, the center of the image can be perfectly sharp focus while the edges of the frame (which are further away) are very slightly soft. Split the difference and see if your overall result improves.
- unless your end use requires maximum resolution, try downscaling your final images incrementally from 8k to something more in keeping with a 4k or 2k film scan. The downscaling algorithms of most photo editing software will do a pretty good job of reducing noise, grain, and unwanted texture.
- by applying noise reduction (or negative clarity or sharpening) to the center of the image in a photo editing app like Lightroom with a soft mask.