Prompted by Shaan's post on DWF precision I’ve been testing to see what impact increasing the DPI has in “real world” conditions. So far I’ve found ramping the DPI up to fairly huge values does increase the DWF file size, but not as much as I expected, and seems to have only a slight impact on plot file sizes.
We draw on A1 sheet at 1mm = 1 AutoCAD unit typically with a 1:200 viewport. For a real world comparison I created a DWF from a store layout at various resolutions then measured a known length in Autodesk Composer aiming for better than 1mm precision. The file has a lot of AEC Mv Blocks (shop fittings) and AEC Spaces (departments) with solid hatch fills. The table below shows the results using the DWF6 ePlot.pc3.
| DPI | DPI Factor | File size KB | File Size | Length (mm) in AutoCAD | Length reported in Composer | Accuracy | Plot File to Hp800 Plotter MB |
| 400 | 1 | 84 | 1.00 | 25446 | 25000 | 98.25% | 1.56 |
| 101600 | 254 | 102 | 1.21 | 25446 | 25400 | 99.82% | 1.61 |
| 1016000 | 2540 | 158 | 1.88 | 25446 | 25446 | 100.00% | 1.69 |
It was a bit of a concern that the file size nearly doubled but it seems this is because the initial file was so small. Publishing a 20 sheet drawing set for our office (Site, Building, Fit-out Plans and Elevations) with lots of hatch fills resulted in the file growing from 2.5 MB @ 400 DPI to 3.0 MB @1,016,000 DPI. Multi-sheet Store Layout sets, about 1 MB @ 400 DPI, grew by 10–20%.
While this increase is noticeable its not a bad trade off for better than 1mm precision over large distances.
PS: Wow, the table pasted from Excel into BlogJet worked fine!
