In this first post of the series, I will cover the differences between these two lenses as well as the best settings and focus distances. Knowing what to expect in advance will save you a lot of frustration when reviewing your shots, as you can stick with what works (at least for me). You can then just focus in one setting and adjusting your strobe power based on the light conditions.
The main objectives of this test are two: find out the best focusing distances for each focal length and the different outcomes with aperture values. As a bonus, we will also see which of the diopters suits better to the RX100 M6.
Test Scenarios
Starting from the minimal focal length for each diopter, we will take a picture of the same subject from the furthest distance possible (8-9 cm as this is the minimum distance we will be able to focus with the RX100) with each possible aperture value.
We will repeat the same process moving closer to the subject in increments of 1 cm.
We will repeat the process incrementing the focal distance to the following values: 47 mm (minimum for CMC-2), 81 mm (minimum for SMC-1), 100 mm, 150 mm, 200 mm (maximum focal length of the RX100 M6).
Notes
Our main objective is to find out the best focusing distances, thus we will be using a focus light instead of strobes and keep the shutter speed fixed to 1/200. This will give us consistent results and will simplify the analysis.
Executive Summary (Conclusions)
Here are the conclusions for those who do not want to spend time reviewing the tests:
CMC-2 is better for this camera than the SMC-1. Gives you more flexibility since the starting focal distance is 47 mm instead of 81 mm **On land focal distances. Underwater is around 55 mm for the CMC-2**. You can shoot subjects the size of a golf ball or even a bit bigger. I cannot appreciate any significant difference in terms of image quality.
Use manual focus with focus peaking. It will help you see what is in focus.
Stay 8-9 cm away from the subject. If you go closer, focus peaking will mislead you and still show the target on focus (possibly the eyes), but it will be soft. The result may be usable, but not excellent.
Stick with F11 to maximize the focus area. Is already minimal, so a bit more will save some shots.
Don't go below 1/200 shutter speed. You have strobes, compensate the light with them. I try to shoot at least 1/500.
Tests
Case 1: Minimum focal distance with the CMC-2 (47 mm)
This is a crop from the subject to evaluate the image quality but this is the focal length for your largest subject. Something with a surface of a golf ball or a bit larger will fit, but of curse just the foremost part will be in focus.
Using 'Focus Peaking', I'm moving away from the subject first and come close until the peaking area starts to show on the screen. My target are the eyes, therefore I keep moving forward towards the subject until the eyes are 'RED' (my focus peaking color). At this moment, I will also have part of the face in red, not the nose or the mouth as they are closer to me (even just 1 or 2 mm...). This is the sweet spot to shoot as you get the eyes sharp and the area around and a bit behind in focus (see the ears). But not the parts that protrude like the mouth or nose.
I feel that the best results are at 8 cm or 9 cm form the target (eyes). I can see much difference between both. In the last image at 7 cm, you can feel the soft focus on the eyes. You can still use it in social media as far as you do not crop it too much, but you are not going to win any competition with this one. The ears, of curse are very sharp.
Original Images:
Where you want to be ZONE :
Between F11 and F8 and 7 to 9 cm from the subject (click to enlarge for more detail, but the head is not the original size. The originals are in the table below)
Case 2: Minimum focal length with the SMC-1 (81 mm) vs CMC-2 (81 mm)
In this test we compare the results at the same focal distance (81 mm) with both diopters. You will see that the SMC-1 offers a bit more magnification at the same focal length. This was a surprise to me since Nauticam advertises x 2.3 magnification with the SMC-1 and x 2.8 with the CMC-2. To simplify the comparison, I am looking at the best results that are archived at 8 or 9 cm from the subject, using F11, F10, F9 and F8.