Any conversion to .sid from another format can appear slightly darker, or otherwise altered.
It can be a single file -OR- a mosaic of any input image(s).
Generally, when we see the SID image resulting in darker images, this is generally due to 16 bit images and how they are displayed to the screen in the viewing application.
- 8 bits maps directly to the monitor.
- 16 bit data needs to be stretched.
The viewing application and any stretching modifications applied to the source -VS- .sid files.
- The .sid views differently than the source image(s).
You will want to take a look at what application you are using where you are seeing these tonal differences.
- Is any stretching is being applied to the image in the viewing application you are using, such as ArcMap?
- When viewing the tif and sid in GeoExpress, can you see any differences there?
The answers normally lie in the responses to the questions above.
Please refer to the GeoExpress 10 Users Manual for details on what types of files and compression are supported.
If you have any additional questions please submit a support request for further assistance