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JPEG image files, a format commonly used for photographs and other complex still images on the Web, is an image that allows for lossy compression. Lossy compression reduces the file by permanently eliminating what looks like redundant details. It uses certain ‘tricks’ based on how the human visual system works to take away information, and the removing information can be barely seen. However, it does save bytes. As a result, fine details in certain areas of the image are obliterated. However, if your image is already in a high resolution, this change is difficult to distinguish. Which explains why we always try to capture images at the largest resolution. Compressing JPEG images downgrades the quality of the image. However, there’s a sweet spot where you can make a trade-off between file size and image quality. This article will provide you with an idea of how much image degradation is acceptable versus what file size is too big.

Firstly, you may wonder what the difference is between reducing ‘resolution’ and ‘file size.’ Image resolution, generally described in pixels per inch(PPI), refers to the number of pixels in an image. The more pixel information it has, the higher resolution it is, which results in a crisp image. In summary, pixels have no set size, they just expand or contract to fill the space available. Let’s take a look at the images below.

Difference between image size and image resolution_higher pixel

640×426 pixels

Difference between image size and image resolution_less pixel

80×52 pixels

These images have a different number of pixels but they fit the image size by expanding each pixel. As a result, the resolution of each image is significantly different. If you reduce resolution, the number of pixels will be cut down resulting in a pixelated image.

However, when you compress file size, a different algorithm will be applied. It reduces the size of the image without losing a single pixel from the original file. It adjusts the quality of the image by discarding unnecessary data, for example, limiting the colors used in an image; fewer colors means there’s less data to run around. Let’s make this easy to understand.

Before compressing an image, each pixel has a different value; 0.12, 0.1234, 12.1, 12.123, 21.12, 21.1234. After you compress the image, the values are 0, 0, 10, 10, 20. Previously, the image had 6 values, whereas following compression, only 3 values are present in the image, which saves up 50%. This transformation cannot be reversed, but it will improve the speed in which it takes to load your image. In short, the number of pixels remains intact. Instead, detailed information will be taken away when you compress the image.

Difference between reducing resolution and compressing image file_Original image

Original image

Difference between reducing resolution and compressing image file_Reduce 50% of resolution

Reduce 50% of resolution

Difference between reducing resolution and compressing image file_Compress 50%.

Compress 50%

Of course, each person has a different standard of the acceptable image quality. You may need to find the sweet spot by experimenting with the quality and size to discern what ratio will yield the best savings at the best quality levels. To save you time and trouble figuring this out, use the table below as a guide. You can also compare each 3D virtual tour according to the different compression rate. As an example, take a look at the image quality comparison in the 3D tour below. (embed link Click this link)

Export Quality Setting in Lightroom

100% of the export quality in Lightroom
80% of the export quality in Lightroom.
60% of the export quality in Lightroom.
40% of the export quality in Lightroom.
20% of the export quality in Lightroom.

As you can see in the above images, by the time you get down to a compression of 40%, you can begin to see noticeably different pixelated colors and halos. Therefore, the recommended compression rate is about 40%.

correlation between the file size and the image quality

This inverse proportion graph shows a correlation between the file size and the image quality. As you can see, the file size drops drastically when the image quality decreases from 100% to 90%. After you reduce the image quality to 90%, the slope keeps getting smaller and smaller as you move to the right. For that reason, the quality of the image is more important than the file size when the image quality level is smaller than 90%.

You can use PTGui to reduce the JPEG file size when generating panoramic photos. Alternatively, you can also use Lightroom or Photoshop. It should be noted that you need to compress photos individually in Photoshop. You can also use free web apps such as Toolur to reduce your JPEG file size.

After stitching your 360º panoramic photos in PTGui, you can decide on the JPEG output quality. The quality ranges from 0 to 100 and you can insert. your desired value. It is recommended that you select a range between 50 to 100 percent.

Compress image file without losing quality in PTGui.

Reduce JPEG quality in PTGui

In Lightroom, you can resize multiple images at once. Select an image or all the images you want to export out of Lightroom. Go to File > Export (Ctrl+Shift+E) and adjust a Quality slider or type the value. We recommend setting the quality between 40 and 80 percent for a web and 3D virtual tour. You may want to select a higher value if you need to print out your files.

Compress image file without losing quality in Lightroom.

Reduce JPEG quality in Lightroom

In Photoshop, you can determine your JPEG quality when you click save or save as. You can then choose your ideal image quality by adjusting the percentage scale, where you can select a number in the scale from 0 to 12. The recommended scale is between 4 and 7.

Reduce JPEG quality in Photoshop

Using AE Bracketing Method

Bracketing is the method of taking generally three photos, one using the camera’s standard settings, one underexposed and one overexposed. This technique is used to get a properly exposed image with a single shot without having to post-process the image separately. You can choose to use auto bracketing using a built-in camera preset to take several bracketed photos.

Bracketed photos can be processed in HDR (High-Dynamic-Range Imaging) that reproduces a greater dynamic range of luminosity than what is normally possible so that the overall quality of the photo is improved.

To take 360º photos using bracketing method, set your camera to M (manual) mode. Set the aperture to 8 then choose AE bracketing mode. Depending on your camera, you can have exposure options. The more photos you take, the better quality you get. However, normally 3, 5 or 7 sets are recommended considering the file size and efficiency when post-processing. Check the level of exposure by pressing the shutter halfway to find the median exposure. Set the median exposure then take photos overexposed/normally exposed/underexposed. For instance, Take 7 photos at each exposure value from -3 to +3(-3, -2, -1, 0, +1, +2, +3).

Additional Tips

  • If the camera is shaking while shooting, it may cause many problems including blurred images. Use a release to help you shoot, especially when doing a long exposure shot.
  • Set the value of F to the highest possible number (at least 8 or above) and the distance at infinite manually.

HDR Photos

Put all images taken using AE bracketing into PTGui Pro and process them. You can have the results processed by each exposure and stitched through HDR. The image below shows 7 sets processed at each exposure.

The image shot underexposed shows better texture of the sky, while the image shot overexposed have clear separation in shadows. When the dark and bright areas are put together, use AE Bracketing to get a partially detailed image.

Bracketing is the method of taking multiple photos with different exposure values, under/overexposed, and standard, then combine them to get a properly exposed image with a single shot without having to post process the image separately. This method is useful when you want to obtain the best quality 360º photos to create a 3D virtual tour for real estate.

The photo shoot underexposed shows the better texture of the sky, while the overexposed photo has clear separation in shadows. Therefore, you can obtain an image with much more detail and color in both dark and bright areas by mixing them together after taking photos in AE bracketing method.

You can read more details on how to stitch HDR 360º photos in this blog post.

The images below show the stitched photos at each exposure value (-2, -1, 0, +1, +2) and the last image is the HDR photo with all images combined.

You can adjust the brightness of the photo in other post photo editing program.

When taking 360º photos for a 3D virtual tour, try to keep the same exposure for all photos. You can adjust the brightness of the photo in other post photo editing program. Set your camera to manual mode and adjust the exposure in the middle.

When comparing them, you can see that the result of Exposure Fusion is better, especially when looking at the shadow details. Also, as evident in the images below, the HDR photo has better color and contrast.

The HDR photos are combined several images with different exposure values and they ensure the better quality of 360º photos for a 3D virtual tour.

Ordinary photo – No HDR

The HDR photos are combined several images with different exposure values and they ensure the better quality of 360º photos for a 3D virtual tour.

Ordinary photo – No HDR

The HDR photos are combined several images with different exposure values and they ensure the better quality of 360º photos for a 3D virtual tour.

HDR photo

The HDR photos are combined several images with different exposure values and they ensure the better quality of 360º photos for a 3D virtual tour.

HDR photo

Even though the file size is over 7 times bigger and the processing time is considerably longer compared to non-HDR photos, taking auto exposure bracketing and process it to HDR is highly recommended because of its overall better results.

The concept of no parallax point is the most important component to get right if you take multiple consecutive shots to produce a single 360º image. When taking multiple pictures, panorama production will be seamless only when you take a shot with the no-parallax point rotated around the center point.

The NPP (no-parallax point) can be seen as the point of a lens used to determine the rotation point when capturing scenes for a panorama or 360º photo in order to keep foreground and background points lined up perfectly in overlapping frames. The position of this point is at a particular point in the lens called the entrance pupil. It is important that the point is in a constant position while the camera is rotated around it to avoid parallax when the images are later joined together.

Parallax is misalignment that occurs when you don’t rotate your camera at the no-parallax point. To simply explain it, hold you your finger and look at your thumb switching between your right and left eyes. Even though your finger hasn’t moved, it seems as if the finger has progressed from right to left. This is what a parallax is. The same thing happens when you take photos with a camera. When you stitch those two images with a parallax error, the same object will appear twice in the stitched image.

What happens when you see your finger with your left eye and right eye.
The concept of no parallax point is the most important component to get right if you take multiple consecutive shots to produce a single 360º image for a 3D virtual tour of your home.

Photo A : 360º photo with a parallax error

The concept of no parallax point is the most important component to get right if you take multiple consecutive shots to produce a single 360º image for a 3D virtual tour of your home.

Photo B : 360º photo taken above the no parallax point

We have learned from our previous post what gear you need to get good 360º shots. Now that we’ve covered the basics to understand the theory behind this, let’s learn some tips on how to shoot and develop stunning 360º photos, from shooting to editing. In addition, we will be covering the fundamentals of camera settings such as ISO, exposure, white balance, focus and aperture in our next post.

To get a full 360º photo, you need to capture every single space in your surroundings. The number of photos you need for one 360º photo depends on which camera lens and camera body you use.

Let’s begin by determining the no-parallax point using an 8mm fisheye lens.

  1. First mount the ball head, rotator, panoramic head and camera with a fisheye lens.
  2. Set the camera at 90º angle by pointing the lens downward.
  3. Set the focus on a center point with the panorama rotator.
1. First mount the ball head, rotator, panoramic head and camera with a fisheye lens. 2. Set the camera at 90º angle by pointing the lens downward. 3. Set the focus on a center point with the panorama rotator. 4. Rotate the camera back to its original position towards the scene then stand two objects 2 small footsteps apart from the camera and each other. 5. Adjust the location of the camera until the two objects are overlapped at any angle.
  1. Rotate the camera back to its original position towards the scene then stand two objects 2 small footsteps apart from the camera and each other.
1. First mount the ball head, rotator, panoramic head and camera with a fisheye lens. 2. Set the camera at 90º angle by pointing the lens downward. 3. Set the focus on a center point with the panorama rotator 4. Rotate the camera back to its original position towards the scene then stand two objects 2 small footsteps apart from the camera and each other. 5. Adjust the location of the camera until the two objects are overlapped at any angle.
  1. Adjust the location of the camera until the two objects are overlapped at any angle.
1. First mount the ball head, rotator, panoramic head and camera with a fisheye lens. 2. Set the camera at 90º angle by pointing the lens downward. 3. Set the focus on a center point with the panorama rotator. 4. Rotate the camera back to its original position towards the scene then stand two objects 2 small footsteps apart from the camera and each other. 5. Adjust the location of the camera until the two objects are overlapped at any angle.
  1. Once you set the NPP, you don’t need to set it every time you shoot you change your camera, lens or panoramic head. Whatever equipment you use, you must have at least 20% of overlap on each photo. Take one photo first using a remote shutter release. The shutter release helps you reduce slight movement while capturing that may cause blurriness on the image.
  2. Rotate the panoramic head to 90º and take another shot. Make sure the individual photos have sufficient overlaps of about 20%. Take a photo and rotate again and take a photo. Do this the all the way for a whole turn to cover all full 360º. The specifics of this rotation is only applicable when using a full-frame camera body with an 8mm fisheye lens. Please refer to this link for further information on how many photos are required to cover a full 360º photo depending on which camera body and lens you use.
6. Once you set the NPP, you don’t need to set it every time you shoot you change your camera, lens or panoramic head. Whatever equipment you use, you must have at least 20% of overlap on each photo. Take one photo first using a remote shutter release. The shutter release helps you reduce slight movement while capturing that may cause blurriness on the image. 7. Rotate the panoramic head to 90º and take another shot. Make sure the individual photos have sufficient overlaps of about 20%.Take a photo and rotate again and take a photo. Do this the all the way for a whole turn to cover all full 360º. The specifics of this rotation is only applicable when using a full-frame camera body with an 8mm fisheye lens. Please refer to this link for further information on how many photos are required to cover a full 360º photo depending on which camera body and lens you use.

How to stitch a 360º photo using PTGUI

  1. Import the set of photos by clicking Load Images on the upper-left hand side of the program. You can also drag and drop directly from the folder to the program.
360-degree photo stitching with PT GUI
  • Here’s a tip to easily find your panoramic photos. For every set of photos, cover the lens with your hand and take a photo. Use this image to divide every set.
  1. Enter camera/lens parameter or use the automatic option. If there’s an error in your stitched photo, check that you select the right type of lens and camera you used. If you don’t find a right option for your gear, just choose the automatic option or consult PTGui customer service.
Enter camera/lens parameter or use the automatic option. If there’s an error in your stitched photo, check that you select the right type of lens and camera you used.
    1. Go to Crop tab. Adjust the circular crop to cover and match the image size by placing and dragging the mouse cursor on the broken line to get rid of the background. The adjustments will automatically be applied to the rest of the photos.

When using bracketing method, normally the photos are arranged from darkest to lightest. If the image is too dark, proceed to adjust the succeeding brighter image. The rest of the photos will be automatically adjusted. More detailed instructions to process bracketed photos will be covered at the end of this blog article.

Go to Crop tab. Adjust the circular crop to cover and match the image size by placing and dragging the mouse cursor on the broken line to get rid of the background. The adjustments will automatically be applied to the rest of the photos.

(3,4)

  1. Go back to Project Assistant tab then click Align Images. The resulting stitched photo will appear on your screen. For HDR photos, a pop-up bar will appear. Check the result and close window.
Enter camera/lens parameter or use the automatic option. If there’s an error in your stitched photo, check that you select the right type of lens and camera you used.
You can see a stitched 360º photo at the end of the process. Check if there are any stitching errors.
  1. You can modify the image file size, format and quality on the Create Panorama tab after closing the window. The photo’s ratio of width to height should be 2:1. If you need to edit the photo further, choose among the many different file formats. To choose saving location, click Browse. Go to your desired folder location and click Save. Once you’re done, click Create Panorama.
You can modify the image file size, format and quality on the Create Panorama tab after closing the window. The photo’s ratio of width to height should be 2:1. If you need to edit the photo further, choose among the many different file formats. To choose a saving location, click Browse. Go to your desired folder location and click Save. Once you’re done, click Create Panorama.
  1. You can view the 360º image via PTGUI Viewer or other panorama viewing programs.
4 photos are combined to get a 360º photo. (Sony A7R II + Samyang 8mm/Fisheye)
To apply the same settings to the rest of your edits, click File and Make Default.

How to stitch bracketed photos to create a 360º photo

  1. Import the set of photos by clicking Load Images on the upper-left hand side of the program. We took 3 photos at every 90º angle, so one set consists of 12 photos. If you have more than one set, a row will compose of 12 photos plus one black photo per set.
You can create an HDR 360º photos from bracketed photos by combining them in PTGui.
  1. Choose Enable HDR mode and link the bracketed images and choose Exposure Fusion for your HDR method. We recommend Exposure HDR as it creates a more natural HDR image and reduces image noise. Click OK.
Choose Enable HDR mode and link the bracketed images with Exposure Fusion HDR mode to create an HDR 360º photo.
  1. To adjust details of the HDR image, close window and go to Exposure/HDR and color adjust photo accordingly.
To adjust details of the HDR image, close window and go to Exposure/HDR and color adjust photo accordingly.
You can adjust the color of a 360º photo in PTGui by moving the scale bars. If the image is bright or dark, there might be a limit to adjust the color.
  1. Once you’re done, Click OK. Repeat steps for the rest of the photos.