Is there a layman's equation for diffraction?

Started 7 months ago | Questions thread
OP SolB Contributing Member • Posts: 536
Re: Diffraction as a percentage of image width

I am glad you mentioned cropping. I would not have taken that into account.  I prefer to clear things up as early as I can in the process.  Thanks once again Mark

I only tend to pixel peep during post-processing in order to evaluate where I may need selective noise reduction as well as sharpening. If I clear things up at 100% magnification I rarely have trouble down the line with the 13x19" print.


Mark Scott Abeln wrote:

SolB wrote:

Thanks Mark. This is exactly what I was looking for.

You're welcome.

However, it might make more sense to ignore the pixel width and instead measure diffraction as a fraction of the entire picture width. I like to pixel peep as well as the next photographer, but civilians instead usually view prints whole and entire from a reasonable distance.

One fairly reasonable criterion is that diffraction won't be particularly noticeable if the blur width is less than 1/1500th the total image width—but no pixel peeping! One nice thing about this method is that the f/stop value will be nearly equal to the diagonal width of the sensor in millimeters! So f/43 for the 43 mm wide full frame sensor, or f/28 for APS-C, f/22 for Micro 4/3rds etc. Of course if you end up cropping an image, you'll have to take that into account as well, so if you end up only using half the image width, you'll have to divide the f/stop value in half as well.

These are rather shockingly high f/stop values, especially considering that values a quarter of these are usually recommended, and of course the images will look soft if you do zoom into them, but on the other hand, these f/stop values are routinely used by macro photographers.

Cactus at f/22 on a Nikon APS-C camera:

Post (hide subjects) Posted by
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark MMy threads
Color scheme? Blue / Yellow