Assignment 1 – Pixel Science
The first assignment was a short exercise investigating what goes into making an image photoreal, and where we cross that threshold. From my previous research into the different pixel science techniques, I used it to inform my practice with this assignment.
Taking a pre-existing scene in Maya where I explored materials, I trialled different techniques, rendered in Arnold, and documented the result. The following stills explore file output; resolution; colour space; lighting; sampling; and camera.
1. EXR, 1920 x 1080 p (HD), 8bit colour management, samples 3/2/2/2/2/2, focal length 35:
Figure 1 displays what happens when you try to open a .exr file. EXRs are a special file that are multi-pass and multi-channel, meaning that render passes and channels are stored in the file format itself. It is also lossless in compression. This makes the file format best for photorealistic renders and compositing, which makes sense as it was designed by visual effects artists at Industrial Light and Magic to help with their pipelines (Elwyn, 2023). With the mass of information stored within the file, it cannot just be opened in an image viewer, as it is designed to be opened in an editing or compositing package.
Figure 2 is a screenshot of the opened EXR file in the software ‘Krita’. The results of the EXR render are a very crisp render, free of artefacts. However, one point of note is that the colours appear washed out in the EXR format, as opposed to the render view in Arnold. This is because the colour information in an EXR is linear, with no gamma correction; while PNG, JPEG, and TIFF are typically sRGB, with gamma correction applied on monitors. This means that EXRs should be gamma corrected.
Another point to keep in mind is that this screenshot may not be a true representation of the EXR as the screenshot itself is a PNG file, even though PNGs are usually lossless in compression.
The sampling was put at 3/2/2/2/2/2 for camera (AA)/diffuse/specular/transmission/SSS/volume indirect (see Figure 3). Sampling will influence shot noise. Figure 4 shows the EXR image zoomed in. The quality is still acceptable. However, there is a small amount of noise in the transparent object. This could be improved by increasing the samples slightly.
The image file is 32,427KB and the render time was 3 minutes and 59 seconds.
2. JPEG, 960 x 540 p, 8bit colour management, samples 3/2/2/2/2/2, focal length 35:
The JPEG format has compression loss. Furthermore, 960 x 540 p is half HD. The results in Figure 5 are fuzziness and noise in the objects, particularly the glassy transparent materials. The reflections in these objects are not as clear. However, the colours are true to the render view in Arnold.
Overall, the lower quality of this image is enough to break illusion of the glassy objects being real. Furthermore, the colour correction pre-applied to this render oversaturates the colours, which also breaks photorealism. Although, the image gives a good overview into what a render should look like, without having to wait for long render times, as this image took 22 seconds at the lower quality settings. Its file size is also much smaller, being 229KB. Therefore, the JPEG format and half resolution is best when sharing updates on a scene because it is quick and efficient, but it is not good for final outputs and renders. This is because the low quality will be even more obvious and noticeable on a big screen; this can instantly take an audience out of an immersive scene. We can especially see this demonstrated when we zoom into the image (Figure 6).
TIFFs can be compressed with and without loss, have no compression, and have a colour range up to 32bpc. This makes TIFFs very powerful. The focus of this render was to see how sampling affects renders. Here, we can see that setting every sample value to ‘1’ has caused the image to have noise and fireflies everywhere in the scene. With the TIFF file format, 16bit colour management and HD resolution, this render should be clear and rich with colour once we target the noise.
To target noise, I isolated the AOVs in the render view. The diffuse, specular and transmission appeared to be where the noise was particularly coming from (see Figures 8, 9 and 10).
Figure 8 – Diffuse, samples 1
Figure 9 – Specular, samples 1
Figure 10 – Transmission, samples 1
The file size is 16,201KB and the render time was 5 seconds. In the following test, you can see the results of increasing sampling for these AOVs.
4. TIFF, 1920 x 1080 p,16bit colour management, compression none, colour space RAW, samples 3/3/3/3/2/2, focal length 35:
The results in Figure 11 are very clear and the reflections are sharp. By strategically targeting the AOVs, I increased samples where necessary. There is hardly any noise. The overall image is darker than the render view in Arnold, like was the case with the EXR result. This is due to TIFFs having a vast amount of colour information like the EXR. Furthermore, increasing colour management to 16bit provides more colour in the scene that was not scene in the Arnold render view, nor in the JPEG render (see Figure 12 and 13).
Figures 14, 15 and 16 illustrate the results of increasing the samples for diffuse, specular and transmission (refer to Figures 8, 9 and 10 to see the results before this). These AOVs were each raised to 3 samples:
Figure 14 – Diffuse, samples 3
Figure 15 – Specular, samples 3
Figure 16 – Transmission, samples 3
The results demonstrate the importance of sampling on renders. The file size is the same as the previous render, 16,201KB; but the render time was 3 minutes and 29 seconds, unlike the 5 seconds of the previous render. This suggests that increasing samples will not affect you file size, but it will increase your render time. Therefore, it is important to only raise samples where necessary.
5. PNG,1920 x 1080 p, 16bit colour management, samples 3/3/3/3/2/2, focal length 12:
The PNG file format at HD and higher samples has retained a clear look. The colours look the same as the Arnold render view, like with the JPEG, so the colour range is not as vast as EXRs or TIFFs. The PNG format is lossless in its compression. The decreased focal length zooms the camera out dramatically and warps the backdrop. This demonstrates how a camera in the same position can warp perspective by playing with the focal length. This can make camera movements more dynamic and interesting rather than keeping the focal length at the standard 35.
The file size is 5,800KB and the render time was 1 minute. The file size is much smaller than the EXR and TIFF, and renders at a fraction of the time. It can be a good option for final render output because of its high quality and lossless compression. However, its colour depth is not as broad as the TIFF and EXR format, which makes those the better option for compositing.
6. TIFF, 1920 x 1080 p, 16bit colour management, samples 3/3/3/3/2/2, focal length 35, exposure of AiSkydomeLight:
As the results of test 4 seemed to be the best outcome so far, I decided to keep the next few tests the same in its settings with slight tweaks to observe the effects of different factors. In the previous tests, each render used a plain AiSkydomeLight with an exposure of 1. With Figure 18, I increased the exposure to 3. Figure 18 shows the results, which are blown out. The translucent objects have completely been lost in the light; the light emitting objects are still visible because they are not absorbing light; and the plastic material is only half visible still as the underneath is not absorbing light while the top is.
The size of the file is 16,201KB and the render time was 3 minutes and 21 seconds. The results suggest that exposure will not affect file size and will hardly affect the render time. Exposure will easily fill an entire scene, which is why you should not go too high with it or else you will blow out elements in the scene.
7. TIFF, 1920 x 1080 p,16bit colour management, samples 3/3/3/3/2/2, focal length 35, HDRI:
Adding a HDRI image to an AiSkydomeLight can transform the light and colours in a scene., changing the way a scene looks. Using the HDRI in Figure 19, Figure 20 shows the results. The HDRI has filled the scene with an overall cool tone. It is very saturated which detracts from photorealism.
Figure 19 - Wronkowski, G. (no date) Modern Evening Street HDRI • Poly Haven, Poly Haven. Available at: https://polyhaven.com/a/modern_evening_street (Accessed: 10 October 2025).
Figure 21 is a close-up of the results. There is notably grain across the render. We can observe that the information of the HDRI can cause noise in renders.
The file size is still 16,201KB, and the render time was 3 minutes and 45 seconds. Like with exposure, it appears that HDRIs do not change file size and hardly affect render times. However, with the added noise from the HDRI, samples will need to be increased. As samples are increased, render time will be increased.
8. TIFF, 1920 x 1080 p,16bit colour management, samples 4/9/8/3/2/2, focal length 35, HDRI:
Targeting the AOVs as I did with previously with test 3 and 4, I increased the samples to 9 for diffuse, 8 for specular, and 3 for transmission. There is a very slight difference in the results, with a small decrease in noise. However, there is still some despite the very high sampling, as observed in Figure 23:
From observing Figures 24, 25 and 26, we can see that diffuse is still causing noise even with samples being increased to 9. Furthermore, transmission could have had samples increased slightly more to remove the noise of the transparent ball.
Figure 24 – Diffuse, samples 9
Figure 25 – Specular, samples 8
Figure 26 – Transmission, samples 3
While sampling made a slight difference with the noise problem and does not add to the size of the file (still at 16,201KB), the render time was 34 minutes and 37 seconds. This is unreasonably long to observe a small difference, taking 10 times longer than previously.
A better way to tackle this should have been to increase the samples on the AiSkydomeLight itself.
9. TIFF, 1920 x 1080 p,16bit colour management, samples 3/3/3/3/2/2, focal length 35, no HDRI and no AiSkydomeLight:
Observing the effect of HDRIs and light again, I removed the AiSkydomeLight from the scene, only keeping the area lights so that we see the objects.
With no HDRI, there is hardly any grain in the scene. The area lights doing the lighting work also empathises the highlights and shadows in the objects. As a result, Figure 27 can pass as being photoreal.
The file size is 20,091KB and the render time was 3 minutes and 45 seconds. When comparing to test 4’s results, we can observe that lower lighting hardly affects render time, but it does increase file size.
10. TIFF, 320 x 240 p, 16bit colour management, samples 3/3/3/3/2/2, focal length 35:
Figure 28 has all the same settings as test 4, except it is at a much lower resolution than any of the other renders. 320 x 240 p is an outdated resolution that has a 4:3 aspect ratio rather than the HD 16:9. The lower resolution means that there are fewer pixels to display the image, therefore the render is fuzzy and grainy. This is not a good output format as of 2025, when we now have 2k, 4k, and 8k resolutions.
The file size is 601KB and the render time was 10 seconds. The low file size makes resolution renders good for sending and sharing, so it can be best for sharing updates on a shot. However, I would recommend a JPEG format and half HD at the very least (as seen in test 2) as the file size will be even smaller and the quality will be more acceptable.
The results highlight that TIFFs at a minimum resolution of 1920 x 1080 p are the best for achieving photorealism, apart from EXRs that are the best for compositing because they store all render passes in the file. However, samples, lighting and HDRIs can affect the believability. Samples can affect noise in a shot, which will be especially noticeable on a big screen. Exposure, if set too high, can blow out objects within a scene, making readability difficult. HDRIs can make a scene more photoreal in some instances, but they can also make a scene oversaturated in other instances, such as in test 7 and 8.
This exercise has made me more conscious of the technical skills behind what makes renders photoreal. This is something I will be testing more with my future projects.
Autodesk (no date). Removing Noise – Arnold for Maya. Available at: https://help.autodesk.com/view/ARNOL/ENU/?guid=arnold_for_maya_tutorials_am_Removing_Noise_html (Accessed: 10 October 2025).
Camber Film School (2019). Video Aspect Ratio Explained – How Different Aspect Ratios Affect Your Video Style [video]. YouTube. Available at: https://www.youtube.com/watch?v=E-dUveGINTg (Accessed: 11 October 2025).
ExplainingComputers(2022). Explaining Image File Formats [video]. Available at: https://www.youtube.com/watch?v=WblPwVq9KnU (Accessed: 10 October 2025).
Goulekas, K. (2021) ‘Acquisition/Shooting’, in Okun, J.A. and Zwerman, S. (eds.) The VES Handbook of Visual Effects: Industry Standard VFX Practices and Procedures. 3rd ed. New York: Routledge, (2) pp. 106-118.
Stump, D. Ollstein, M. Reisner, D. and Wall, W. T. (2021) ‘Acquisition/Shooting, in Okun, J.A. and Zwerman, S. (eds.) The VES Handbook of Visual Effects: Industry Standard VFX Practices and Procedures. 3rd ed. New York: Routledge, (2) pp. 188-212.
Wronkowski, G. (no date) Modern Evening Street HDRI • Poly Haven, Poly Haven. Available at: https://polyhaven.com/a/modern_evening_street (Accessed: 7 October 2025).