Stimuli are shown with low resolution in Pavlovia

Dear Psychopy experts,

I have a recognition memory task that works perfectly on the local machine (and also online). In the task I show different fonts associated with a variety of abstract words. I created .png files given that pavlovia does not support fonts (they need to be installed in the local computer). So what I did I created different high resolution image for different fonts and words. The participants will have to process details of the font so it is important that the images are in high resolution. However, while this works fine on my local machine, the images are not loaded with high resolution online…neither if I use my 13-inches laptop, nor a bigger screen. This is really weird since the images have properties which are fixed irrespective of screen (11667 X 2917, dpi = 1440). Due to low granularity of the images I cannot start piloting. Can anyone help me with this?

Thank you in advance

Hello Lollo,

as long as you use fonts which are commonly installed you can specify fonts. But I assume that you are not using commonly available fonts.

The picture dimensions you are giving are in what unit? If they are pixel, you pngs exceed the dimensions of most monitors. Also, a device can not exceed its resolution. So your fine resolution won’t help on most monitors. Too large images slow down display and prolong downloading.

The browser does not alter the image resolution. It is determined by your display and video hardware.

Do you specify a height and width for your images in PsychoPy?

To evaluate the problem by others, you probably need to upload an example.

Best wishes Jens

Dear Jens,

Thank you for your reply.

No, exactly I have around custom fonts which are not part of Microsoft fonts, reason for which I had to create pictures.

The dimensions are in pixels. However, I am using “norm” as units to run the experiment both locally and online since I read that this is the best option (together with heights) for online studies.

I do specify the size which is $(1.3, 1.3) using “norm” as units. This was due to the fact that I was using many pixels so I wanted the image to be bigger. I guess I should try to reduce the pixels of the images (for example 1500 x 980 or similar) and print a bigger font on them?

This is an example of a stimulus that appear to be good on a local machine

…and this is the same stimulus when I run the experiment online

I also would like to say that this discrepancy only occurs for some stimuli, but not for all and it is not clear why to me given that all the pictures have the same properties.

Any clarification would be appreciated
best wishes

Hello Lollo,

I see that parts of the k and the s are cut off but you are not running the experiment in full screen mode. Does this happen in different browsers as well?

Using norm the window ranges from -1 to 1 in x and in y. So, I do not know how PsychoPy interprets 1.3 norm units. Also, setting the height to 1.3 and the width to 1.3 results in square stimulus only if your monitor is as high as it is wide which is hardly the case. Height is better for images because the aspect ratio is maintained. And you are using images displaying text.

I would first try to reduce the white space around the words unless you want to cover the window background. That allows you to increase the relevant area.

I assume that instead of using a fixed size you might want to consider to have your participants scale the stimulus to a comparable object. You don’t know what monitors your participants will be using so a fixed size might be unfavorable.

Best wishes Jens

Dear Jens

Thank you for your suggestion. The fact is that it is not only a matter of cut edge. Some stimuli appear with high definition, and some others with low pixel resolution despite them being ALL in high definition. It seems that this is inconsistent across stimuli and I do not understand why.

I will try to change them in height now and see if anything changes
Thank you