Backward compatibility is always appreciated, there's no doubt about it. However, sometimes a console's implementation can be lacklustre, either due to technical difficulties or laziness on the manufacturer's part. Depending on who you ask, the 3DS' DS/DSi mode can be said to fit in either: your only options are to either play games upscaled to the 3DS' screen resolution, which includes a blurry filter that cannot be turned off, or in native res mode, which is hardly ideal as it doesn't make use of the entire screens - thus introducing big black bars all around. Due to it, some people preferred playing DS(i) titles on past consoles as it made a number of games look significantly better without any compromises.
But things are finally starting to change with the release of TWPatch made by @Sono. After lots of research and reverse engineering, he made a patcher that is able to change how TWL_FIRM's image upscaling behaves. A total of nine different scaling filters are available (not counting Nintendo's default one), several of which are able to make your games look much sharper than before! In order to give you an idea of what to expect, here is a comparison taken from the thread (made by @youny43 - left: default / right: patched) :
For the curious, here's a list of the included filters:
Filter list said:
- Nintendo default
- Sono's crisp (original patch)
- Sono's crisp (tweaked)
- Zero interpolation (double pixel)
- Linear interpolation 1
- Linear interpolation 2
- Sharpen test 1
- Linear sharpen 1
- Darken crisp
- Darken Nintendo
The patcher works on both Old and New 3DS models as long as they are running Luma CFW. You need to have enabled loading external FIRMs and modules in Luma's configuration menu, otherwise, the custom filters won't be applied. The process can take several minutes, so be sure to have enough battery charge (and patience) before proceeding. If you're unsure on which one to apply, you can preview how they'll look inside the homebrew app and compare it to Nintendo's default one.
If you want to try this yourself, make sure to read the instructions & remarks in @Sono's post before downloading (linked below).