MSL Images & Cameras, technical discussions of images, image processing and cameras |
MSL Images & Cameras, technical discussions of images, image processing and cameras |
Aug 16 2012, 11:05 PM
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Senior Member Group: Members Posts: 2228 Joined: 1-December 04 From: Marble Falls, Texas, USA Member No.: 116 |
I'm still trying to figure out a number of things about the new images we are trying to work with. Assuming others are likewise trying to learn, I thought I would open this thread to create a place for such discussions.
I'd like to start out with a comment about raw image contrast. There have been several postings in the main threads about whether or not the MSL raw images have been stretched like those from the MER missions. I am certainly no expert on this, but it looks to me as if the MSL images have not been stretched at all. I haven't tried to analyze all of the image types, but the hazcams and navcams have pixel brightness histograms that are very different from their MER counterparts. This attached image compares MER and MSL navcams along with their luminosity histograms. The MSL images clearly are not using the entire, available range of brightness values, whereas the MER raws do. For this reason, the MSL raw images can usually be nicely enhanced by simply stretching the distribution of brightness across the full 256 value range. -------------------- ...Tom
I'm not a Space Fan, I'm a Space Exploration Enthusiast. |
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Sep 8 2012, 12:12 AM
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Senior Member Group: Members Posts: 1465 Joined: 9-February 04 From: Columbus OH USA Member No.: 13 |
Anyone know why the "full frame" raw MASTCAM images are sometimes 1648x1200, usually 1536x1152, rarely 1600x1200? I believe the specified image size for the camera is 1648x1200. Are the smaller sizes scaled or cropped?
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Sep 8 2012, 12:49 AM
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#3
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Martian Photographer Group: Members Posts: 353 Joined: 3-March 05 Member No.: 183 |
Anyone know why the "full frame" raw MASTCAM images are sometimes 1648x1200, usually 1536x1152, rarely 1600x1200? I believe the specified image size for the camera is 1648x1200. Are the smaller sizes scaled or cropped? True full frame is as you say. 48 columns are dark or null (see the MAHLI paper that has been linked several times). The corners are quite vignetted, so for some purposes 1600x1200 may not be what is desired. For other purposes, it is handy to have multiples of 64 for the size; multiples of 8 are required. Those come from JPEG compression of both the thumbnail and the image. I'd speculate that once we're well past CAP2, you'll see NxM * 128 most often, and 1648x1200 more rarely, and others quite rarely. But you never know. |
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Sep 8 2012, 01:37 AM
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Senior Member Group: Members Posts: 1465 Joined: 9-February 04 From: Columbus OH USA Member No.: 13 |
But you never know. Thanks... I've been working out a method to unwarp the images based on the CAHVOR camera specification for MASTCAM. Hard to say how to apply it to the cropped images though. I guess scale 1536x1152 up to 1600x1200 and then add the 48 dark columns back in. It's easier with the NAVCAM images because they at least come in at 1024x1024 as specified. I'm wondering if stitches would work a little better using such rectified images. Here's a before and after of a NAVCAM shot--it's a real subtle correction: -------------------- |
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