Mark Z Posted August 8, 2018 Share Posted August 8, 2018 The Sunny 16 rule applies to terrestrial scenes, and it needs to be adjusted for something like Mars, which is farther from the light source (the Sun) than the Earth. Mars receives a little less than half the sunlight as does Earth. In addition, the light from Mars needs to pass through our entire atmosphere, which scatters and absorbs light, further diminishing its brightness. For a photo of Mars, Sunny 16 may need to be modified to Sunny 9.5 or even Sunny 8. 1 Link to comment Share on other sites More sharing options...
Ed_Ingold Posted August 8, 2018 Share Posted August 8, 2018 Even at "Sunny 8," which is quite reasonable, the shutter speed at f/2.8, ISO 100 would be 1/800, not several seconds needed for star images and the milky way. Link to comment Share on other sites More sharing options...
Sandy Vongries Posted August 8, 2018 Share Posted August 8, 2018 Even at "Sunny 8," which is quite reasonable, the shutter speed at f/2.8, ? Link to comment Share on other sites More sharing options...
Vincent Peri Posted August 8, 2018 Share Posted August 8, 2018 ? Later in the same sentence, he says the shutter speed is 1/800 ("at f/2.8," which he put first in the sentence.) Link to comment Share on other sites More sharing options...
maris_rusis Posted August 9, 2018 Share Posted August 9, 2018 One should not underestimate how small Mars appears. Even when it is closest and biggest in apparent size it is about visually equivalent to a billiard ball 600 yards away. That's way too tiny for a DSLR and zoom lens to give detailed images. Remember, the best astronomers using the biggest earth based telescopes after a couple of centuries of research effort could not produce consistent maps of the place. We needed satellites and rovers to do that. Link to comment Share on other sites More sharing options...
sjmurray Posted August 9, 2018 Author Share Posted August 9, 2018 What's interesting is that I'm getting different sized Mars on different shots with the same setup just shooting several shots in a row. I have been guessing that the size differences must be due to focusing, since I am manually focusing. However, the supposedly "out of focus" larger images look really like Mars in larger photos, even to the point of showing what looks like some surface detail. Here's first example, shot with a D7100, 18-105 lens, iso 1250, 160 sec, f 8. Looks like Mars Link to comment Share on other sites More sharing options...
sjmurray Posted August 9, 2018 Author Share Posted August 9, 2018 this one is the same night, a few minutes later, f 5.6, iso 1250, 1/2000 sec. despite shorter shutter speed/ f stop, the image is brighter and much smaller. Better focus? Link to comment Share on other sites More sharing options...
chulster Posted August 9, 2018 Share Posted August 9, 2018 this one is the same night, a few minutes later, f 5.6, iso 1250, 1/2000 sec. despite shorter shutter speed/ f stop, the image is brighter and much smaller. Better focus? Yep, I'm going to go with that explanation. I should have thought of that at the beginning. It is interesting and somewhat puzzling that the misfocused shots show more apparent detail than the well-focused ones. I wish an optics expert would explain that. Link to comment Share on other sites More sharing options...
kmac Posted August 9, 2018 Share Posted August 9, 2018 How not to photograph Mars - with handheld digital compacts. The image was cropped for a better view The movement of the camera was probably less than 0.5 mm while the electronic shutter went through it's paces, and it took an age before the orange light stopped blinking, but the Canon 960 is well known for it's slow processing of data Next attempt of course will be tripod plus self timer, tonight hopefully. The settings I was using for these first shots were: full 3x zoom which meant digital as well as optical. 1/3 stop underexposure (set manually in "Settings"). "Center" focus. ISO 200 and the rest were automatically set by the camera. These settings finally brought out the red color of the planet whereas with settings of faster ISO and exposure, the planet was white Link to comment Share on other sites More sharing options...
glen_h Posted August 9, 2018 Share Posted August 9, 2018 (snip) I have found that even manual Loxia lenses have to be backed off slightly from the infinity stop. Stars are essentially point sources (~ 0.02 arc-seconds), so any error is significant at the pixel level and 42 MP resolution. Atmospherics will produce random patterns in star images, similar to astigmatism or an incipient cataract. (snip) As well as I know, it is traditional for longer focal length lenses to focus past infinity. That way, with thermal expansion and such, you are sure to still be able to focus to infinity. In many cases, there isn't enough depth of field to focus to the stop. -- glen Link to comment Share on other sites More sharing options...
glen_h Posted August 9, 2018 Share Posted August 9, 2018 The question about mars size reminds me of the story about how in Galileo days, and probably for years after, it was thought that stars were not so far away. There was no understanding of diffraction, which makes the visible stars not a point when viewed through a telescope. (Even more, with less than perfect lenses.) When I look at diffraction limited images, I notice that all stars look the same, and you think that they might have notice that. -- glen Link to comment Share on other sites More sharing options...
Mark Z Posted August 9, 2018 Share Posted August 9, 2018 Steve, it really isn't possible to see detail on Mars with your lens. What you're getting are out of focus images of what is nearly a point source, and "details" are most likely atmospheric effects. With Mars being rather low in the sky for you, these effects are worsened - you are looking through at least three air masses (three times the amount of air compared to looking straight up) when you look at Mars. People who are getting nice images of Mars, including surface details, are using longer focal lengths and image stacking (often thousands of images) to wring out details. See the Solar System Imaging and Processing forum on Cloudy Nights. Cloudy Nights Forums 1 Link to comment Share on other sites More sharing options...
sjmurray Posted August 9, 2018 Author Share Posted August 9, 2018 Love that hand held shot kmac! Looks like something out of a science fiction movie. 1 Link to comment Share on other sites More sharing options...
Supriyo Posted August 9, 2018 Share Posted August 9, 2018 I think it would be impossible to see any features using a 105 mm lens, but let’s do some basic calculations using Mars diameter: 6794 km Mars distance at the closest in 2003: 55 million km Diameter of Mars image at 105 mm focal length: ( 6794 x 10^3 / 55 x 10^9 ) x ( 105 x 10^-3 ) = 0.013 mm For a 20MP full frame DSLR (resolution roughly 5477 x 3651 pixels give or take), one pixel size is roughly 0.0066 mm Therefore, the Mars image would be about 0.013/0.0066 = 1.97 pixels in size. Assuming perfect circle, the number of pixels contained within the Mars image would be about (1.97)^2 / 4 x 3.14 = 3 pixels. With just 3 pixels in area, there won’t be any real features disceranble, and whatever variations in brightness are seen in the image would be a combination of atmospheric diffraction and in-camera antialiasing/smoothing. This of course doesn’t take into account atmospheric lensing at low altitudes or diffraction, both of which can enlarge the Mars disk somewhat, although that wouldn’t improve things much. 1 Link to comment Share on other sites More sharing options...
stuart_pratt Posted August 9, 2018 Share Posted August 9, 2018 I got a firmware upgrade for my 70-300. Nanu-nanu......... 3 Link to comment Share on other sites More sharing options...
chulster Posted August 10, 2018 Share Posted August 10, 2018 I got a firmware upgrade for my 70-300. Nanu-nanu......... Colors seem off. I guess you win some, you lose some. Link to comment Share on other sites More sharing options...
Moving On Posted August 10, 2018 Share Posted August 10, 2018 The thought was rolling around in my head, behind a wry grin the last day or so, you beat me to it Stuart..... Great Minds and all that..... ;) You must have rested your elbows on the car hood. Link to comment Share on other sites More sharing options...
stuart_pratt Posted August 10, 2018 Share Posted August 10, 2018 The thought was rolling around in my head, behind a wry grin the last day or so, you beat me to it Stuart..... Great Minds and all that..... ;) You must have rested your elbows on the car hood. Yup, but with a slight rotation to avoid blur due to the rotation of the earth. You just gotta practice! Link to comment Share on other sites More sharing options...
Ed_Ingold Posted August 10, 2018 Share Posted August 10, 2018 I got a firmware upgrade for my 70-300. Nanu-nanu......... What is the attribution of this photo? If not the poster, then it should be a link, not an image. Link to comment Share on other sites More sharing options...
Moving On Posted August 10, 2018 Share Posted August 10, 2018 (edited) True, but I think most realize it was a joke..... Look closely at the lower left corner.... Is it ok to take a picture of a picture? Computer screen? T shirt logo? With all due respect for copyrighted material, there are many public domain sources. Taking a screenshot “digital photo” seems perfectly acceptable in such cases. Category:NASA images - Wikipedia “Since its creation in 1958, NASA has been taking pictures of the Earth, the Moon, the planets, and other astronomical objects inside and outside our Solar System. Under United States copyright law, works created by the U.S. federal government or its agencies cannot be copyrighted. (This does not apply to works created by state or local governments.) Therefore, the NASA pictures are legally in the public domain.” Here ya go...... NASA Images Mars Exploration Image Gallery Edited August 10, 2018 by Moving On Link to comment Share on other sites More sharing options...
Ed_Ingold Posted August 10, 2018 Share Posted August 10, 2018 Is it ok to take a picture of a picture? Computer screen? T shirt logo? These might constitute fair use if properly (and prominently) attributed. That said, is is against the rules for posting on PNET if you aren't the photographer. A photo of a T-short incidental to the content and intent of a photo, in a public place, is generally permitted. If your intent is to show the copyrighted artwork itself, generally not. Link to comment Share on other sites More sharing options...
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