How many times have you read or people say,
“You should stop down the aperture to get sharp photos”? Use F22.
Or something in those lines. Situation can get worse at times when using Raynox. The lens structure of Raynox makes taking larger than life photos somewhat difficult. People who use Raynox tend to stop down the aperture because bigger F number = greater DOF. The result? Well you do get the photo but it will not be as sharp as you think.
The reason is obvious. Diffraction. But I am not going to bore you in talking about what is diffraction and optic physics. There are many articles on it and you can have a look. I recommend you read this article:
I am not writing this article, to explain what is obvious. Even when you are shooting with a 5D Mark IV and a MPE or a Canon 550D with a reverse lens, the optic physics stand as is and you as a photo macrographer have to understand this situation. As you understand this situation, you will start to find ways to stay in the good range. Approaching the subjects at different angles, variations etc can let you stay one step above the limitation.
So why ALWAYS big F number to take macro photos? Why it is an edge to edge sharpness contest? I feel the online facebook scenario, is slowly changing towards showing everything as tact sharp vs. keeping reality in check and molding the depth to create macro art. If a certain group show some photos, immediate everybody want to imitate the style or angles or whatever. The imitation requirement brings up demand for workshops. Some workshops tend to cater to what is the hot running trend and fix on it. Instead of catering to functionality of photo macrography, quick sessions are conducted where it is sort of a crash course. Low aperture number, ISO should be low and shutter speed should be fixed at flash sync speed.
Why I cannot change these settings? Why do I have to keep my settings locked if I am purchasing a camera that boasts a good dynamic range? Why do I have to keep my aperture fixed to a big number to get “sharp” photos? I keep posting my photos on my wall and here on the website. Viewers do ask me why you not lowered down the aperture? This is the basic principle of photo macrography. Mostly, these viewers do not account for the reason of diffraction. You see diffraction, not only impacts high magnification photos but also impacts low magnification photos. You don’t get the chance to excuse yourself of using a big number just because you are shooting below 1:1.
Big F number is a general stress to the rig if you keep shooting those numbers all the time. Dialing the F number to F22 gives stress to the lighting system. If a scene is sufficiently possible to be captured at say F13 with a particular reading of light, each stop down of aperture is step up of the flash intensity. For the same scene you now need more light as you stopped down further. Higher intensity is lower freezing capacity of the subject during the exposure. A flash light at 1/200 will have lower freezing power than 1/2000. This can mean you will run of battery quicker than expected. Big F number can also bring out dust spots in the photos and make them prominent in the photos.
Let us have a visual example of how different aperture values affect the sharpness of a photo with diffraction and almost no magnification.
Behind the scene photo first.
The test subject
The setup for the experiment is a two tailed spider. I have setup the Canon 80D and the 100mm macro on a tripod and on a rail. The rail and the tripod are locked in place. The AF is off after some test shots to bring the spider into focus. The following base settings are kept.
Shutter speed at 1/200
I am only changing two things. The aperture and my light intensity. Change of light intensity is needed as light at F8 will not be the same for F14 and vice versa.
All the photos are cropped at the same spot on a rough 50% basis. Photos are resized to 1024px to put up here and sharpened. I have marked the aperture values in yellow.
Here is a matrix of all the aperture photos.
Now it starts to become clear that, the lens has its own sweet spot where it gives an best performance.
There is a noticable difference in sharpness between F8 and F22 even when the sharpening settings in post are exactly kept the same.
In the case of Raynox, sharpness of Raynox depends on the quality of the host lens. Beginner Raynox users forget this aspect and expect magical photos with Raynox and a telephoto lens stopped down a lot. With that setup you are in the effective aperture and diffraction territory so that is also something to look into.
I am not saying you should never take photos with F22. I take when the scenario demands it. If there is a rare subject/scenario which demands the entire frame to be in focus, you have to throw away the physics limitation and get the photo. Many have also taken big prints and showcased in exhibitions and got awards/applauds. It is natural that beginners and enthusiasts will be eager to follow their footsteps in mimicking their mentors. But the light physics are here to stay, long after you have shut down doing photo macrography.
Things start to change when you stop mimicking mentors, brush up on general theory and begin applying it whenever it is possible. Then you start to realize the true value of your own gear.
At times it is ok to prove your mentor’s point, otherwise.