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Post by Peterj on Sept 17, 2018 22:55:56 GMT
Moon Illusion I'm not suggesting that you create composite images blended in post processing and exaggerate the moon's size. My intent is to explore how to use this illusion rather than scientifically explain it; for interested parties here’s a scientific see sentence below below covering a multitude of explanations [btw there's no single accepted explanation]. My simple "explanation" is the moon appears larger when viewed close to horizon than directly overhead.
Wait a minute – what about all those images showing the partially risen moon looking absolutely huge? What’s happening here is the belief in the illusion and actually capturing an image showing the illusion – no not necessarily post processed but an actual image. Have a look at this image and read the relatively simple explanation.
This table top demonstration uses every day items captured at different focal lengths of my zoom lens. All images are hand held and at longer focal lengths are not be perfectly focused. The camera was moved in relation to the objects in order keep the larger object about the same size in the frame.
Moon velocity
While researching Moon Illusion for the Lunar Eclipse on 1/20/2019 the moon's velocity information was highlighted a few times. When capturing moon images one must be aware of the moon’s relative velocity to the earth.
The camera was tripod mounted, manual mode, ISO 100, f8, 1/60 sec, AWB, lens extended to maximum [600 mm], moon framed, time lapse set to start when the shutter was pressed, 30 second interval between exposures, sequence terminated when the moon was about to leave the frame.
The image is an 11 second composite [22 layers] created using On1 Layers Module blending mode for the top 21 images set to lighten. No adjustments made to any of the layers. The take away here is a high ISO is required because the moon is moving FAST across the sky. The noise resulting from high ISO can be negated by taking multiple images and stacking them together in post and using noise stacking in Photoshop. Most noise is random and will cancel out using this method. I checked the camera to insure the sequence was being captured hence the missing image.  |
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Post by Bailey on Sept 17, 2018 23:36:06 GMT
Hi Peter,
Your first link "document" points to this thread when I click it.
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Post by Bailey on Sept 17, 2018 23:57:46 GMT
Hi again Peter, This is an interesting subject  Moon Illusion - my understanding of what you are describing is more commonly known as zoom/lens compression. The way I explain it to people is something like this example: You are pointing and focusing your telephoto lens (focal length say set to 500mm) at point A, 20m away from you. A point B in the background is 100m away from you. The distance from A to B is then 80m. Now let's assume the len's magnification at 500mm in 10x. I am simply using round numbers in this example so don't take these numbers literally. Looking through the lens, point A will appear to be 2m away and point B 10m away from you and the distance between A and B will appear to be "compressed" to 8m. Consequently points A and B appear to be much larger than they actually are. So at low altitudes from the horizon, apart from the moon looking larger because of the extra distance through the atmosphere the light from it has to pass plus other reasons, the moon will appear even larger through a telephoto lens due to zoom/lens compression. Moon Velocity - I'm not sure what you define as high ISO. Yes, your shutter speed cannot go too slow otherwise you might see some motion blur due to the moon's orbiting motion and the earth's rotational movement. In this photo I used my Tamron 150-600mm lens with settings f9, 1/60s, iso 400, 600mm. The noise at this ISO was very minimal and very easy to remove in ACR. |
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Post by Peterj on Sept 18, 2018 0:43:19 GMT
Thank You for catching that Bailey - it's been corrected
Bailey - 100% spot on. I chose the title to match the document [incorrectly linked at first]; Moon Illusion has plenty of hits when searching the Internet
High ISO is relative to the camera type and age. I'm assembling a training program for my local camera club whose members don't all have the latest and greatest; my goal is for anyone wishing to photographically capture this coming January's total lunar eclipse can do so regardless of equipment owned.
Thank you for your informed responses - this helps me as I complete the training sessions.
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Post by Bailey on Sept 18, 2018 0:56:40 GMT
Hi peter, Hi Peter, Your first link "document" points to this thread when I click it. Thank You for catching that Bailey - it's been corrected Are sure the link has been corrected? It still points to this thread. This is the bbcode of your link in your post:
here’s a scientific [a href=""][/a][a href=""]document[/a] covering a multitude
You can view your actual bbcode by clicking the bbcode button near the bottom left corner of the post editor when you are editing a post or "quoting" someone else's post in a reply. The first [a href=""][/a] is redundent and shouldn't be there.
The href attribute of the link [a href=""]document[/a] needs to contain the url the link is supposed to go to when clicked. Yours is empty so it defaults to this thread when clicked. I can't edit your posts so if you are having trouble creating the link, hopefully one of the mods. or admins. can insert the url of your document into the href attribute. HTH |
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Post by Bailey on Sept 18, 2018 1:25:09 GMT
... Thank you for your informed responses - this helps me as I complete the training sessions. No problem. Good luck with your training sessions and photographing of the eclipse in January |
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Post by Peterj on Sept 18, 2018 3:24:20 GMT
Bailey, Thanks for your advice, but I choose to delete the link and simply paste the exact url in text.
Maybe linking to a pdf is problematic. It was more than I wanted to learn today  |
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Post by Bailey on Sept 18, 2018 4:45:53 GMT
[offtopic] No problem Peter. I have copied the text of your document url into the dialog box from the "Create Link" icon in the post editor's toolbar and created the following link. It works just fine. Peter's Document LinkThe bbcode then creates the following code for the link: [a href="http://www.uww.edu/Documents/colleges/cls/Departments/Psychology/Mccread_Moon_Illusions.pdf"]Peter's Document Link[/a]When you create the link, you would put the text "Peter's Document Link" in the box labelled Text and the url http://............ in the box labelled URL. Like Firefox, I would think all other mainstream browsers have a built in pdf reader to open url's that point to a pdf file, so urls pointing to a pdf file should not cause any problems for users.
Also, most if not all mainstream browsers are smart enough to detect plain text, like you now have in your op, that is actually a url and so will convert it to a link in the user's browser anyway.
Class dismissed.........and back on topic now [/offtopic] |
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Post by hmca on Sept 18, 2018 11:35:31 GMT
Using Chrome on my Mac, the document downloads rather than opening. Just adding this as I hadn't noticed the download the first time I tried the link.
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Post by Bailey on Sept 19, 2018 11:18:30 GMT
[offtopic] Using Chrome on my Mac, the document downloads rather than opening. Just adding this as I hadn't noticed the download the first time I tried the link. Hi hmca, Generally speaking, downloading is probably the safer option than opening directly, especially if the document is from a web site that you don't know is trustworthy or not. By first downloading the file you can then scan for viruses or other "nasties" before opening the file. By opening the file directly in the browser you could release any "nasties" hiding/embedded in it onto your computer. In my Firefox settings, I have it set to ask me if I want to download or open a file when I click on a link to it on a web page. Most of the time I download first. Each browser should have a setting somewhere to control how you want to handle links to files. [/offtopic] |
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