JPEG compression

[Donovan]

I recently presented this topic, but I need to re-post it, since I am not happy with JPEG compression on affinity, and need some advice please.

 

I attach two images, one has been exported and compressed to JPEG at around 1mb (its now a screenshot PNG image, but it replicates exactly how the JPEG turned out), the other is the affinity version.

 

The JPEG image is clearly unusable.  1MB should be absolutely ample for a very good quality JPEG image.

 

Is this an Affinity software issue? Like most people, I do need to send small JPEG files to friends and family, and at 1MB, and indeed smaller, they should look fine.

 

Can anyone help on this? Thank you.

 

Jason

[walt.farrell]

For anyone to help in a satisfactory way, we'll probably need the original image file, or .afphoto file, before export so we can play with it ourselves.

[Donovan]

Thank you. I do appreciate your help. I attach the file.  However, I am finding that with many files, I have the same compression issues. 

_DSF9718StonegateWoods.afphoto

[Donovan]

Ive attached the RAW file too, if that might help. I used the Overlay Paint tool on the sky to darken it. Jason

_DSF9718.RAF

[walt.farrell]

Thanks, Donovan. Next questions:

1. What size (pixel dimensions) are you trying to export it. You're currently 6032px x 4032px, which is 24.32 megapixels.
2. What color format and pixel depth are you trying to export it? You're currently RGBA/16.

I doubt that anyone whom you're casually sharing with needs an image that large, and probably they don't need 16-bits of color, especially if you're sharing a degraded form like JPEG.

Keeping it your current size and pixel depth you're at over 1MB even choosing 5% quality for the JPEG export. If you resize to 754x504px during export, even at 100% you end up with about 800KB. Cut it down to 80% quality and you're down under 200KB (even at a 16-bit depth).

[Donovan]

Im a beginner at this so please bear with me.  I merely did some editing in RAW straight from the camera, (including Overlay paint tool for the sky), then in Persona, amended the brightness, and then exported it to JPEG and moved the slider so the JPEG file size was around 1MB.

[Donovan]

I amended the brightness in Persona, only because I realised it was still too bright after RAW editing

[walt.farrell]

2 minutes ago, Donovan said:

Im a beginner at this so please bear with me.  I merely did some editing in RAW straight from the camera, (including Overlay paint tool for the sky), then in Persona, amended the brightness, and then exported it to JPEG and moved the slider so the JPEG file size was around 1MB.

I understand. But if you want small files, with good quality, you'll need a slightly more complex export workflow. Specifically, you will need to reduce the dimensions of your photo to a more reasonable height/width in pixels, I believe.

In the Export dialog from File > Export you can adjust the dimensions, and choose a resampling method. Then worry about the quality. For example:

[Donovan]

Thank you Walt - that is exactly what I needed to help me get through this problem. Much appreciated.

[R C-R]

Also keep in mind that JPEG compression is lossy, meaning even at 100% "quality" some details will be lost. (There is a non-lossy form of JPEG compression but it is rarely used & Affinity does not support it.)

What this means is not only do the pixel dimensions determine how much compression can be applied without noticeable artifacts appearing in the export, so does how much pixel-to-pixel detail there is in each image you export to the JPEG file format. (Technically, this kind of detail is high frequency image content.) Areas of solid color have essentially no high frequency content so they compress very well without adding compression artifacts but ones with lots of color variations (even ones not very noticeable to the eye) have lots of high frequency content so they do not.

A very common source of high frequency content in digital photographs is noise, which adds nothing to the sharpness or quality of the photo, but can easily go unnoticed unless the photo is examined carefully at high magnification levels. So among the other techniques for getting compact JPEG images without sacrificing too much useful detail, the ones demonstrated in the Affinity Photo - Export Compression Efficiency video tutorial are worth considering.

[Donovan]

Thank you for your additional content. I'll be watching the video. Jason

[Terri D]

I know this topic is over a year old, but I have been having similar issues. I am an artist and take high res photos of my paintings. When I create smaller jpegs for website/social media I often have difficulty getting good jpegs. The compression makes them very soft/blurry that doesnt properly reflect the painted surface. It is a lower quality than when I used to save jpegs through photoshop. I've kind of settled on bicubic sampling to keep them as crisp as possible, but still not really happy with it. Any tips would be appreciated. I will watch the video link given above. Thx.

[Fixx]

Serif has "kinda" admitted the quality of Affinity JPEG export is not top notch. It is "kinda" recommended now to use additional software if top quality JPEGs are needed. For example, export from AP to full size TIFF and batch resample/sharpen/convert with XnConvert.

[R C-R]

1 hour ago, Fixx said:

Serif has "kinda" admitted the quality of Affinity JPEG export is not top notch.

As I remember it, what they have said is they use a lossy JPEG compression algorithm that is computationally efficient & therefore fast, but the tradeoff is its compression efficiency is not as good as some others. The result is that for any particular JPEG "Quality" setting, the exported file size will be larger than if they used a more efficient one.

As a workaround for that, I use ImageOptim, a free Mac app that offers a wide range of compression algorithms, a few of which are so extreme that it can take several minutes for them to compress a file to its smallest possible file size. 

[appearsharmless]

Just wanted to add a +1 for ImageOptim. I know turning to a third-party app is an aggravating workaround, but every time I use ImageOptim I think: "Whoa... I can't believe this thing is free."

[ModalNode]

In May 2021 Google will be changing its SEO and SERP algorithms to favor websites that load the quickest. In order to prepare for this change, one can use this tool to get a feel for both mobile and desktop issues:

https://developers.google.com/speed/pagespeed/insights/

The results for all of the websites I manage yielded this:

"Serve images in next-gen formats: Image formats like JPEG 2000, JPEG XR, and WebP often provide better compression than PNG or JPEG, which means faster downloads and less data consumption."

 

I'd love it if Affinity could could incorporate these formats in to Photo. 

[John Rostron]

The main problem seen in your images is the clouds. Jpeg compression does not cope well with areas of similar colour; it tends to produce banding.

I uploaded your .aphoto file and exported it as a .jpg file at 100%, 60% and at 15%, and at 15% with Lanczos resampling. The 100% and 60% show no obvious banding, but the 15% versions do. The file sizes are (in the same order) 33.2MB, 4.6MB, and 1.7MB.

The images below are the exported jpegs cropped to just show the cload area. It will display at 100% if you click on it twice.

At 100%:

60%:

15%:

The 15% version with Lanczos sampling was not visibly different and was the same size.

My suggestion is that 1MB is too small for what you want, but around 4MB (60%)  would be OK.

John