Conditional Tag to Display Images from Grid field

Hi,

I have one grid field with a maximum of 4 rows, every row is a file to allow editors to upload from 1 to 4 images.

The first image is required and others are optional.

First image: main_image

Optional images:

additional_image_1 additional_image_2 additional_image_3 additional_image_4

To display the required image in template i use this tag:

{product_images:main_image}

To display additional images i want to use a conditional tag in template. I’ve tried with:

{if product_images:additional_image_1} <img > {/if}

It doesn’t work. Anybody can give me directions of how code should be?

Thank you.