Proper downsampling of the larger thumbnail will induce some loss of sharpness, unless compensated for by an additional sharpening pass. When rendering to a significant enough larger size than the what the thumbnail offers, a more accurate calculation is done for the size needed, based on the original Raw data.
That's my view of the situation as well.
So, reducing the thumbnail size to less than the fit area dimensions seem like a useful workaround.
While that approach indeed addresses the blurriness, it comes with two downsides:
- The efficiency gain that previews should normally provide is lost. Re-rendering from scratch is "expensive" and shouldn't be necessary.
- Often adjusting images at higher magnification levels (e.g., 100%) becomes very bothersome when the preview size is set too low. During the adjustment C1 seems to revert to the preview (at least in some situations) and that preview is way too small to support good feedback during adjustments. Only after one stops making further adjustments, C1 re-renders a proper quality image again. This leads to a very jarring experience during adjustments.
The second downside does not always occur. So far, I haven't noticed a pattern.
Overall, I have to revoke what I've said about C1 11 and its preview quality. I initially thought it consistently handled previews better than C1 10 as the blurriness during adjustments (when intentionally using nominally too small preview size settings) does not always occur. However, I encountered it frequently now and this means that the situation is still unsatisfactory.
My suggestion to the C1 team, offer an option for automatically sharpened previews when resampling is involved.
Have you submitted your suggestion via a support case?
I hope that everyone suffering from the unsatisfactory preview situation lets Phase One know by
creating a support case. Phase One relies on the frequency of requests to determine what priority they should assign to resolving issues.