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Posted: July/30/2019 at 12:48pm  
Image Resizing Tutorial and Recommendations 
for RCSB Site Supporters.

(last updated 01/01/2024)

Please take a few minutes and read the ENTIRE tutorial. This will help you to understand what you are doing and why you are doing it and you will walk away with an understanding of digital images most people don’t know. 

One thing new site supporters have trouble understanding is why we require image file sizes so small when compared to other sites that do not set this requirement. 

The reason for the image file size limit is because RCSB displays its images in posts in an in-line flowing style (as opposed to having all the images grouped at the bottom of each post as thumbnails) that includes in-line images mixed with text to help the individual posting tell the story. Think about trying to read a post and match a tiny image thumbnail up to what you are reading like on the others sites when a process is being discussed. It can be a real pain to follow. The small amount of extra effort on your part here helps you tell the story of your build in a way that no other site offers and others appreciate!

Since our images are inline, we have to manage the amount of data that is sent down to the browser when you or another member views any topic page. Think of it like this, if a topic page has 20 images on it and they are all 4 Megabyte in size that is EIGHTY MEGABYTES of image data that has to download to your browser just to show you one page of images. That would take a long time to  download on a medium to slow connection which is utterly unacceptable. You, me, nor anyone else would wait that long for a page to load. Now you know why we limit the file size. 

Now that you understand WHY we do this, let’s talk about why images are so large and how we can make them smaller without loosing the physical size.

How digital photos are constructed
Digital photos are made up of an arrangement of “pixels” (a small dot of color) of a certain width, height, depth, and most importantly density. It’s the pixel density or “resolution” that accounts for the majority for the images file size. Most modern digital cameras and phone/tablet cameras generate images which are 600 - 1200 pixels per inch (ppi) resolution or higher. This is great if you plan on having your pictures printed as photographs, but for posting in a thread and viewing it on a monitor it is a total waste. Even the highest resolution consumer monitors can only display images at a resolution of 96 ppi. As you can see, most of that camera’s high resolution is wasted on images posted on the internet and does nothing but slow down the download to your browser and take up excess disk space.

Also, digital cameras (like your phone or tablet) have no idea what you are going to do with the picture you take so they make them the highest resolution possible by default in case you want to make photo prints. Of course we just need to display them on the monitor.

More about resolution
Sometimes you may hear others talk about dots per inch(dpi) or pixels per inch(ppi), for the sake of simplicity in this tutorial, you can view dpi and ppi as pretty much the same thing. There are some subtle differences but they are both measurements of pixel density and interchangeable to the average person. Here is an extreme close up of a LCD screen. You can actually see the pixels.

Fixing the problem
So you are like, ”OK, I get it, so how do I lower the image resolution of my images?” Actually it’s quite easy. There are many different ways to achieve this, I am going to recommend a couple of image utilities that process “batches” of images lowering the resolution and resizing them for you listed by Operating System. These are by no means the only programs out there that do resizing/changing resolution, but the ones I have found that will do the job adequately.

Note: While not nearly as critical as resolution, an image’s width and height can also play a role in increasing the overall file size (the space taken to store the image in disk). As of the writing of this tutorial the MAXIMUM recommended image WIDTH is 1280 pixels for an RCSB post. This may be raised as monitors get larger and mobile devices get higher quality displays included with them. This width is mostly to make the image easy to view without having to scroll of the right to see the rest of it. Most people use a width of 1024 for their images as it is usually a preset on most image processing utilities.

Software Recommendations

The software recommended here is just that, a recommendation. There are many other software packages that can do the same thing. So don’t feel tied to any of these solutions.

Windows 10/11 - PhotoRazor
This is by far the easiest utility for this purpose to use on the Windows platform. PhotoRazor preserves your original images and it is the utility I use for posting on my Windows PC. It automatically changes the images ppi to 96ppi when you process them. Here is a link to download PhotoRazor

To use PhotoRazor the directions are simple. 

1. Pick an image in the folder you want to resize by clicking the “Choose Folder...” button, navigating to your image folder and selecting one of the images (don’t worry, it will load all the images in that folder) and click “Open”.

2. Set the Size and Quality. I set the maximum width to 1024. The slider won’t go that far but you can select the numbers and type in “1024”. The picture Quality should be set to 65% as this will give great quality but will compress the image file somewhat.

3. Select the photos to resize (or simple leave “All selected) by holding down the [CTRL] key and clicking each image on the right you wish to resize. Also make sure the ‘Save to Sub-folder” is where you want it. I leave as “Small photos as it simply creates a folder in the current folder you are working in with the resized photos.

4. Press the “Resize Photos Now” button and watch it do it’s thing!

Just be sure to navigate to the “small photos” folder when you go to upload the images into your post.

Apple PC’s (OS X) - Preview
You actually have a tool built into your Mac or Macbook to do this already. In addition to being a photo viewer, the Preview app for Mac offers basic image-editing functionality. If you want a quick and easy way to resize images, this built-in Apple app will do the trick. 

First you need to find the image you want to resize. To start the process, you’re going to find the image you want to resize on your Mac. To do this, open the Finder app and then locate the file in question. 

Once you have found the images you wish to resize then select them all and click one to open it in the preview app. You will see thumbnails of all the selected images down the left or right side of the window. Click Edit on the menu and then Select All.

Now click Tools on the main menu and then Adjust Size.. Here you can simply set the width to 1024 and make sure the Resolution is no higher than 96 pixels/inch (the default 72 is fine also). Make sure the “Scale proportionally” and “Resample image” checkboxs are checked then click ok. This will resize all the selected images.

Now time to save them... Click “File” on the main menu and click “Export Selected Images”. This will pop up a file save dialog that ask you to choose a directory to save these new files in.

Now you have images ready to be posted. You may have to play with them some to get the size right depending on the quality of the compression (.jpgs and .png’s)

There is a great video on YouTube that will show you visually what I just described.

A good article on how to do this (don’t click the ads).

Also here is the “official” support page for doing this from Apple.

Linux - Converseen
Converseen is a free batch image processing application available for various flavors of Linux . With Converseen you can convert, resize, rotate and flip an infinite number of images with a mouse click. You can get Converseen by clicking the link below:

Lets get started...

1. After opening Converseen click on “Add Images” on the toolbar (big green plus sign). Navigate to your images and hold down teh shift key and select each image you want to add. Once they are loaded click the “Check All” button on the toolbar.

2. Next, click one of the images so it shows up in the preview. Make sure all the images are still checked. Now scroll down below the image preview and make sure the “Link aspect with selected image” and “Maintain aspect ratio” checkboxes are checked.

3. Set the image width to 1024 px (the height should change when you click in the next box. Next set the X and Y resolution to 96.

4. Scroll down and confirm or change the Save in directory and if you want to change the images names.

5. Now, click the image settings button and if the images are jpg’s set the quality to 65 (This is still considered high quality and you cannot tell the difference between 65 and 100). If the images are .png’s set the Png compression to 65 also then click ok.

6. Now click the convert button on the toolbar and all the images will be resized and saved in the new directory you specified ready to upload to RCSB.

Smartphones / Tablets
RCSB does not officially support smart phones or tablets because the site is a rich environment that requires a large amount of interaction that is difficult at best, on a phone or tablet for most users. Browsing the site casually is fine on these devices but you wouldn’t try and write a document, create a spreadsheet, or edit images on a phone or tablet, yet most people complain how difficult it is to write and post rich text and resize images on these devices. It is difficult because it is outside the realm of what these devices were designed for... Simple web browsing, email and social media. That coupled with the small percentage of these devices being used by members (less than 10% as of January 2024) does not warrant the effort to totally redesign and rewrite tens of thousands of lines of code to accommodate a small percentage of users.

That said, if you insist on using these devices then here are some apps we recommend you try. We offer NO support for these as they can change often and as I said before, these devices were not designed to to this kind of work.

iPhone / iPad
Image Compress & Resize

Android Phone’s and Tablets
Reduce Photo Size

Photo Compress & Resize

I hope you found this tutorial useful and if you have any questions, please feel free to contact me via Private Messenger (PM) or the Contact Us page.


Mike Chilson,
RCSB Owner/Founder
My R/C Aircraft Over The Years
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