Hi Void,
Took a quick look at your raw files and not sure why they don't line up, but they clearly don't, as you have pointed out. If I didn't know better, I'd say they were shot at slightly different apertures?
In any case, a simple 100% overlay-difference map shows where they do not line up. I could do it using helicon or even warp tools if it were mine, but I'd be curious as to why they don't line up too.
I have shot many multiple exposure-blended images with Credo80 and IQ250 (for masking reasons with fly-away hair on products and models) and have not experienced this problem. But Mine are in studio conditions using a DF+ standard primes, etc...
Hi, thanks for confirming this!
They were shot at the same aperture and same focus, but the foreground was shot with only the centerfilter, while the sky was shot with both the centerfilter, the ND filter and the ND grad filter. With 2 additional layers of filters the angle of view slightly changes. This distortion is perhaps non-linear and more complicated than the traditional breathing issue that Helicon Focus can deal with.
The reason why I can't shoot both frames with the same set of filters on:
a) I was shooting long exposure for a sunset;
b) For CCD sensors the darkframe NR is vital for long exposure, otherwise the image is completely unusable; (Sony CMOS sensors don't have this limitation)
c) To expose the foreground with ND and ND grad on, I would need triple or quadruple the time as for the sky (with changes of light over the sunset into consideration), which means it's going to be in the 10+ minutes territory;
d) If I expose the foreground before the sunset starts, the darkframe NR countdown of 10+ minutes would occupy the whole sunset phase;
e) If I expose the foreground after the sunset ends, then I would have to wait for the darkframe NR countdown for the sky to end first, after which I would then only be able to shoot a night scene for the foreground. This not only captures the wrong light for the foreground for blending, but also would easily force the exposure time into the 1 hour territory with the same ND and ND grad on (as the light gets dimmer and dimmer), and that would include another hour of darkframe NR countdown, which is totally not practical;
You may ask why I have to shoot so long exposures. Two reasons:
a) Sometimes the clouds are not moving that fast and it would be good to have the extra exposure time to further smooth out;
b) To justify the so called "Long Exposure Mode" of the IQ260 - otherwise why the hell shouldn't I buy an IQ280 instead?
Sadly even a Nikon D5300 can do this scene in just one single exposure and achieve better image quality than the IQ260.
I agree that you might be able to eventually align these bracketed exposures perfectly with dedicated efforts, but life is too short and I have no more time for that.
This is the most important reason why I dumped the IQ260 for an IQ250 instead. Bracketing isn't going to work for me. Sony CMOS sensor is of my taste (i.e. single frame of long exposure straight out of the camera, no darkframe NR, no bracketing, no harassment in post-processing).
