On Feb 14, 2013, at 11:29 PM, Mike Jarvis <notifications@github.com> wrote:

> In galsim/base.py:
> 
> > +                           It is important to keep in mind that the calculation of a
> > +                           galsim.ImageCorrFunc is a non-negligible amount of overhead, so the
> > +                           recommended ways are (b) or (d). In the case of (d), if the same file is
> > +                           used repeatedly, then use of the `use_cache` keyword (see below) can be
> > +                           used to prevent the need for repeated galsim.ImageCorrFunc
> > +                           initializations.
> > +                           (Default `noise_pad = 0.`, i.e., pad with zeros.)
> > +    @param rng             If padding by noise, the user can optionally supply the random noise
> > +                           generator to use for drawing random numbers as `rng` (may be any kind of
> > +                           `galsim.BaseDeviate` object).
> > +                           If `rng=None`, one will be automatically created, using the time as a
> > +                           seed. (Default `rng = None`)
> > +    @param pad_image       Image to be used for deterministically padding the original image.  This
> > +                           can be specified in several ways:
> > +                               (a) as a float, which is interpreted as a constant value to be used
> > +                                   for the padding;
> I'm concerned about the float option here. I don't think we ever want to pad with a non-zero float. Remember, this object is representing a surface brightness profile of a galaxy (or star...), not how that galaxy appears on the final image. So padding with a sky level is an error.
> 

The use case I had in mind was cluster-galaxy lensing, where there is often ICL near cluster centers.  in that case there would be an astronomically motivated non-zero value everywhere (for example, if someone wanted to check how well their software is able to remove that and measure the galaxy parameters).  Is that too crazy to worry about?