Convolve PSF with Image

Hi. I am trying to convolve a PSF I generated with an image to understand the effects of jitter and smear. The generated PSF is blurred out due to jitter and smear and is oversampled such that it is a 200x200 array. The PSF really only spans a pixel, and the full 200x200 array only spans 3x3 actual pixels. The image I have is a 512x512 image that was generated using DIRSIG. I need some help understanding how to convolve my PSF with my image. I think where I am getting stuck is the sampling of the PSF compared to the image. When I try to do imfilter(image,psf) I just get a white thing, which makes me think its a sampling issue. What the right way to go about this? I tried resampling the PSF down to something that is 3x3, but that didnt seem quite right.

Thanks for your help!

Here is my PSF when I plot it in pixel space

Then just doing an imagesc of the PSF array

[Bjorn Gustavsson]

If this is what your PSF would look like on a 3 pixels by 3 pixels region if you could resolve it at 200 by 200 pixels then the 3-by-3 pixel PSF ought to be the sum of the pixels in 67-by-67 pixel regions of that (for your sanity I'd strongly advice you to recalculate the PSF at a resolution of 201-by-201 since that would be evenly divisible into 3-by-3), after which you would have to normalize the PSF too. Since the PSF is rather narrow you wont get much smearing, but this is how I'd interpret your PSF.