Old Good Light: Why still use a 4.7 MP Foveon camera in 2020 ?

Updated on March, 12th 2023

This is an update of the original 2018 post. Test images at 4.7 MP available for download at the end of this post.

"Low Resolution" Sigma Foveon Cameras

From time to time someone asks me why sometimes I still use a 4.7 MP camera today. People usually believe that the more resolution, the better the images are and this is not so simple.

Depending on the use we don't need a high-resolution image. What you need is a proper pixel density to have a good viewing experience. What's this?

For example, if you like to make printed photos, let's say, in postcard size (6x4 inches or 10x15 cm) you don't need a many megapixels image to have a perfect looking print.

This is because the average human eye is virtually unable to see any difference in a printed (or projected) image at more than 300 dpi at a distance of 20 cm. This means that if you print the same image at the same size in 300 and 1000 dpi you simply won't be able to note any difference between them.

Let's do some simple calculations:

For a postcard size print, printed at 300 dpi we need (6 x 300) x (4 x 300) pixels = 1800 x 1200 pixels = 2160000 pixels = less than 2.2 megapixels.

For a larger A4 size (roughly 8.3 x 11.7 inches) we need 8.5 megapixels (8 will do fine)

Larger resolutions are good if you need to crop the image or if you're a pixel peeper and want to have some fun looking it at 1:1 size. For larger prints at 300 dpi, obviously, you will need a higher resolution.

For poster size prints, you usually look at it from a distance and the print resolution can be lowered due to the human vision nature. You can use an online calculator to check what print resolution you need, based on the print size and viewing distance.

Another interesting use for old, low-resolution still cameras, is to make time-lapse images for making videos or to take multiple shots for stitched panorama images.

To display a photo fullscreen on a DCI-4K UHD TV (4096x2160 pixels) we need 8 megapixels to fill all the screen pixels but depending on the viewing distance 4 or 5 megapixels would do fine, since you may not want to stare at the screen from 30cm...

In other words, you may not need the resolution you think.

Those old Sigma cameras, from the pre-Merrill age like the SD14/15 and DP1/2 are more than enough if you don't need really large prints. Images from them can be easily interpolated by a 1.5 factor without any visible quality loss.

An interesting point of the Foveon images is the absence of color alias. It's possible to upscale the 4.7 MP image without any perceivable quality loss to 150% (linear) and with acceptable quality at 200%. The Sigma Photo Pro raw converter is very good for upsizing.

The output resolution of those 4.7 MP cameras (DP1/2 and SD14/15) is 2652 x 1768 pixels.

Upsizing it to 150% leads to a 3978 x 2652 = 10.5 MP, more than enough for an A4 or Letter size print.

Just take a look at this image:

Sigma DP2 sample, from Sigma website
(C) Gris

and this other one:

Sigma DP2 sample, from Sigma website
(C) Gris

Go on... Use SPP to upsize them to 150% and print with a good paper, ink and printer and see by yourself.

Considering the fact that any of those Sigma cameras with 4.7 MP (x3) are very cheap now, it may worth a try.

The last example was done using a Jurassic Sigma SD10, the second dSLR from Sigma and it's just 3.3 MP.

Sigma SD10 image example

The image was first converted from X3F to TIFF using Sigma's own program SPP version 6 and then processed again on Affinity Photo for some color correction and tone curve adjustment. Honestly, it's a very high-quality image, but small. Still impressive today and easily up sizable to 4K to be displayed on a UHD TV or monitor.