Hi Axel, Thank you for all your help. It is greatly appreciated.
Kind regards, Peony > Date: Sun, 26 Aug 2012 12:13:47 +0100 > From: [email protected] > To: [email protected] > Subject: Re: [HDRI] Photosphere "Cannot solve for response function" > > Hi Peony, > > The four images that you uploaded have the following exposure values: > > 0.jpg ISO68 F2.8 0.0666667s 6.32EV > 1.jpg ISO199 F2.8 0.0666667s 7.87EV > 2.jpg ISO200 F2.8 0.125s 6.97EV > 3.jpg ISO200 F2.8 0.125s 6.97EV > > You need a wider range of exposures to cover the dynamic range of the > scene. Visually, the images appear to have almost the same brightness. > They need to noticeable different. See > http://www.jaloxa.eu/webhdr/demo.shtml > for an example exposure-bracketed sequence. > > It is recommended to vary only the exposure time, although in principle, > playing with the ISO sensitivity should work, too. Just make sure the > aperture is fixed, which it is in your example shots. > > The last two images (I don't have your original file names) have exactly > the same exposure. Visually, however, one is a little darker than the > other. This can mean that the EXIF information (aperture, ISO, shutter) > is unreliable. > > You must also mount your camera/smart phone on a tripod. hdrgen can do > some magic trying to align the frames, but it's better to not rely on > it. For accurate results, a tripod is a must. > > You will also need to get hold of a luminance meter against which you > need to calibrate the HDRs. Note that the calibration factor depends on > the white balance setting with which the images were taken. > > I don't know how you can control the exposure times on a smartphone, but > my recommendation would be that you borrow a decent camera and get some > experience with HDR photography before attempting to do this on a smart > phone. Alternatively, invest in a second hand Canon PowerShot and put > CHDK on it: http://chdk.wikia.com/wiki/CHDK. Make sure your model is > supported. This will allow you to take exposure-bracketed sequences > without touching the camera. For most PowerShots, it will also give you > the option of saving in RAW format for when you need the results to be > VERY accurate. > > Hope this gets you started. Good luck > > Axel > > > > From: Axel Jacobs > > Sent: Friday, August 24, 2012 11:16 AM > > To: [email protected] > > Subject: Re: [HDRI] Photosphere "Cannot solve for response function" > > > > Hi Peony, > > > > if you upload your sequence to > > http://www.jaloxa.eu/webhdr/roll-your-own.shtml > > I'll have a look over the weekend. However, as Greg pointed out--don't > > hold your breath. You might have to use a proper camera if you're > > interested in HDRs that are 'as accurate as possible'. What are you > > trying to measure? > > > > Cheers > > > > Axel > > > > > > On 08/23/2012 09:50 AM, Peony Au wrote: > >> Dear all, > >> I am trying to create HDRIs using an Android Smartphone. I have taken > >> six photos ranging from –3 to +3 and have tried to fuse these in > >> Photosphere, however I am getting a “cannot solve for response function” > >> message. Does anyone know how I can create a response curve or what I am > >> missing to create the response curve? I can create a HDR image using the > >> generic response curve, but for my thesis I would need all the HDRIs to > >> be as accurate as possible. > > > _______________________________________________ > HDRI mailing list > [email protected] > http://www.radiance-online.org/mailman/listinfo/hdri
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