The Official Shoot the Moon Thread

navydoc wrote in post #19117139
That's an almost 100% crop. Here's a 200 percenter.

Hosted photo: posted by navydoc in
./showthread.php?p=191​17139&i=i202579706
forum: Astronomy & Celestial

What lens were you using on this photo?

Very nice!

Edit: Now I know! 200mm-600mm!!

So if that is a 200% crop, that means you resampled it up, ie. made each pixel from a 100% crop 4 pixels?

Here are two shots from last Friday 08/28/2020

First shot at 200MM includes Saturn

Second shot at 1200mm

Couple nights ago, RF 800mm f/11 IS STM

Photo from LoneRider's gallery.
Image hosted by forum (1060888)

TeamSpeed wrote in post #19117473
So if that is a 200% crop, that means you resampled it up, ie. made each pixel from a 100% crop 4 pixels?

I was asked if I could show a closer crop and since the first image I put up was almost a 100% crop, the only way I can see to crop in further is to resample. I'm curious why you ask. Is there a better way to crop in closer than 100%?

Here is the full frame before any cropping was done. this was shot at 600mm at a resolution of 61MP.

TeamSpeed wrote in post #19117473
So if that is a 200% crop, that means you resampled it up, ie. made each pixel from a 100% crop 4 pixels?

If there is state of being confused to the power of confused, then I am there.
Never really given much thought to the technicality of cropping, resizing, zooming. Percentages and resampling and pixels.
Resizing as I understand in the simplest form is the image as a whole is reduced in size (resolution-pixels or units of measurement in inches/cms etc) so it can be posted on the internet emailed or similar. This means the space occupied on disk in GBs or MBs is smaller.
Cropping, again in the simplest form, in post is done using editing software and parts of the image are removed keeping only the parts you want. This will enlarge the image on your screen. How this relates %, pixels, resampling etc is over my head. I would like to learn that part of it.

The most you can crop into an image is 100% without altering the base data. So if you view (via LR or photoshop or whatever), or crop and resample and save the file, at any percentage higher than 100%, you are using one of about 5-7 well known software algorithms that resizes each pixel into a number of new pixels that weren't original to the file. Some algorithms are meant to preserve hard edges, some will soften the image, some will just duplicate neighboring pixels.

So going more than 100% means you are going from pixel peeping the actual data into a virtual world where software is creating data for you to look at.

When we say 100% crop, that just means we aren't supplying the full image, we have cropped a small section of the image and made a file from it so we can share it. If we share a file with greater than 100%, we have resampled it to have more pixels before we share it, with results that can vary depending on which method is used.

If you were a caterer, and were paid to produce plates of food for 100 people, and you go set up 10 tables each with 10 plates of food, each table is a 100% crop (of the original agreement of 100 plates of food). Then they come to you and say oops, there are actually 400 people coming. So you take that one table and put 3 more tables next to it, each with 10 plates, and take the original 10 plates of food and spread its food across the 30 other plates (because you cannot go out and make more food, there are no more supplies to do so), and hope people think its filling and yummy. How you distribute a plate of food across 4 plates could impact the visuals of the situation, do you group the food in the center of the plate, do you spread it around the edge of the plate...?

That is what happens when we take a large file, crop out a 100% section of it (whether it is a 100x100, 1000x1000 or 3000x3000 block of data) and share it, vs when we crop out a 100% view, then resize it up, and share the new result (100x100 becomes a 400x400, etc).

I understand the physics of cropping in beyond 100% and the inverse square law but I was not trying to deceive anyone. I felt there was enough information in the original image to resample at that percentage and still retain a reasonably accurate representation of the original, at least at the file size limit allowed on POTN of 1600px on the long side.

No problem, I replied with what I did because a couple others had expressed interest in what 100% vs > 100% means, both in PMs and here on the thread. It wasn't meant to imply anything, just hopefully a bit of education for those that don't get all that pixel-level magic.

One can usually enlarge each dimension of a digital file 20-30% without any really noticeable issues, that is the limit I use, and if I go beyond that, I then am more careful on which resampling method I use, or I do it in stages using a mix of methods.

TeamSpeed wrote in post #19117601
If you were a caterer, and were paid to produce plates of food for 100 people, and you go set up 10 tables each with 10 plates of food, each table is a 100% crop (of the original agreement of 100 plates of food). Then they come to you and say oops, there are actually 400 people coming. So you take that one table and put 3 more tables next to it, each with 10 plates, and take the original 10 plates of food and spread its food across the 30 other plates (because you cannot go out and make more food, there are no more supplies to do so), and hope people think its filling and yummy. How you distribute a plate of food across 4 plates could impact the visuals of the situation, do you group the food in the center of the plate, do you spread it around the edge of the plate...?

Use smaller plates.

OhLook wrote in post #19117692
Use smaller plates.

That could be a 3rd visual, er... resampling method, no doubt!

Here is a brief (ie. the real discussions around these different methods can take pages of documentation) technical doc: https://www.microimage​s.com …chGuides/77resa​mpling.pdf

Where does this matter with moon shots? It will likely be around crater edges more than anything. The rest of the moon, when it doesn't even fill 1/6th of the frame won't likely show too much in the way of artifacts elsewhere.

Many thanks for the explanations. It has certainly helped in understanding, I still need to read and experiment with cropping to grasp all the technical bits. I mean I do crop all the time just need to understand how to explain what the crops are.

If all you do is crop and save out new files and then share those as is, it is up to others on how they view the images. They can choose to look at 100% (pixel in file 1:1 to pixel on the screen), or view less, or view more (software used to view will upsize accordingly). If this is the case, none of this matters really in day to day use for what you are doing.

You only have to worry about the previous posts if you actually crop out something from your images and then actually resize/resample them up, and what the impacts are to the final saved files. It may be good to understand this too when you view someone else's images where they have already resampled their images, cropped or otherwise, so you are able to understand any artifacts you may, or may not see.

Some cameras are better at having their images resampled larger, if they captured a ton of low level detail for example. Some don't render fine detail very well due to the AA filter, perhaps, and resampling those up will just look more muddied.

TeamSpeed wrote in post #19117745
If all you do is crop and save out new files and then share those as is, it is up to others on how they view the images. They can choose to look at 100% (pixel in file 1:1 to pixel on the screen), or view less, or view more (software used to view will upsize accordingly). If this is the case, none of this matters really in day to day use.

You only have to worry about the previous posts if you actually crop out something from your images and then actually resize/resample them up, and what the impacts are to the final saved files.

Now that makes more sense to me. Sometimes when I export a cropped image, say it says 800px X 500px, I have on occasion increased that to 1500px and it automatically adjusts the ratio.
So this would be resizing/resampling up. And thats where its good know what percentage etc I'm going up?


Edited for typo.

4matic wrote in post #19117749
Now that makes more sense to me. Sometimes when I export a cropped image, say it says 800px X 500px, I have on occasion increased that to 1500px and it automatically adjusts the ratio.
So this would be resizing/resampling up. And thats where its good know what percentage etc I'm going up?

Edited for typo.

Yes, if you are actually changing the pixel count from 800 to 1500, then it will apply the same percentage of change to the other dimension too (else you would end up with a long or tall stretched version) to keep the aspect ratio.

Here is a sample of a JPG from camera, a 100% crop, and then 3 different Photoshop methods for resampling that 100% crop up 2x in both dimensions. It is hard to tell the difference at first glance, but there are differences. You can see it more once you enlarge the enlargements to see the effects, like the pixelation effect of one over the others, or the smoother less detailed version of one over the others.

These different methods will handle detail, noise, etc a bit differently at the pixel level. If you find you have to crop and resample to fit the needs of an online printing service for example, it's good to know these different methods and find the one that works the best, and you may find doing resampling steps, like 150%, followed by a 125% with a different method, might be even better.