Conclusion

Large pictures have a negative impact on the download time of an item. There is a lot you can do about this and it's worth to include picture optimization into your workflow by applying what you learned from this article. Sometimes you will find that the file size will only shrink by a few percent, sometimes not at all. And often you will be amazed how much you can achieve with very little effort.

Make your own experiments, try different tools - even in sequence - until you find what works best for you. 

And then enjoy the fruits of your work!