To keep a green object in a green screen in Premiere Pro, there are a few steps that you can follow.
Firstly, you need to import the footage into Premiere Pro. Then, create a new sequence and drag the footage into the timeline. Make sure that the green screen footage is on the top layer and the background footage is on the bottom layer.
Next, you need to add the "Ultra Key" effect to the green screen footage. To do this, select the green screen footage in the timeline, go to the "Effects" panel, and search for "Ultra Key". Drag the effect onto the green screen footage.
In the "Effect Controls" panel, click on the eyedropper tool next to the "Key Color" option. Use this tool to select the green color in the footage that you want to remove. You can adjust the "Tolerance" and "Edge Thin" options to fine-tune the effect.
If there are any areas that are not properly keyed out, you can use the "Matte Generation" options to fix it. For example, you can use the "Pedestal" option to adjust the black levels, or the "Choke" option to shrink the edges of the matte.
Once you have a clean key, you can add your desired background footage to the bottom layer. Make sure that the green object is properly positioned in front of the background. You can use the "Motion" options to adjust the position, scale, and rotation of the green object if needed.
Finally, you can add any additional effects or color corrections to the footage to make it look more natural. For example, you can add a "Light Wrap" effect to blend the edges of the green object with the background, or use the "Lumetri Color" effect to adjust the overall color and exposure.
It's important to note that the quality of the keying will depend on the quality of the original footage and the lighting conditions when it was shot. You may need to make some adjustments to the keying settings to get the best results. Additionally, you should always save your work as you go along to avoid losing any progress.
As a source, you can refer to the official Adobe Premiere Pro documentation or online tutorials from reputable sources such as Lynda.com or LinkedIn Learning.