The last post covered what gear I actually ended up standing behind on the field: the Baader Planetarium Travel Companion 95 (apo, calcium fluoride, 590mm with the flattener) with the Canon EOS R as the corona system on the Warpastron WD-20P mount, piggybacked with the Samyang 135mm and the Canon EOS R50 for wide-angle context. This post goes one step further and is deliberately technical: how did I actually expose, with which values, how were the shots during totality triggered in the first place, and why did the two systems end up running brackets with a different number of steps?
Filters and the Division of Labor, Briefly
Both lenses ran with a custom-fitted Baader AstroSolar film filter (OD 3.8) during the partial phases, which was removed entirely right before totality and put straight back on right after — not really a filter swap, just off and back on. OD 3.8 is the density grade of the film intended for photography; the denser ND 5.0 variant is meant for visual observation with the naked eye and wasn’t used here. The two systems had clearly separated jobs: the EOS R on the apo ran the actual exposure bracket for the corona, the diamond ring, and the prominences, while the EOS R50 on the Samyang was set up more for single exposures of the landscape and horizon shot and didn’t carry the same bracketing workload.
The Partial Phases: Calm, Infrequent Shutter Presses
From C1 until shortly before totality, and again from C3 to C4, the camera fired a single frame roughly every two to five minutes with the film filter on — not for the bracket itself, but to end up with a continuous sequence for a composite of the entire event, from first to last contact. Exposure values during this phase: ISO 100, shutter speed somewhere between 1/250 and 1/1000 of a second, depending on cloud cover and what the histogram on the display was actually showing — it’s worth testing on site rather than trusting a table value blindly, since atmospheric conditions can shift the right value noticeably.
The Final Minutes: Focus Locked, Exposure Ready
Focus on both the apo and the Samyang was checked right after setup and again in the middle of the partial phase — and deliberately left alone after that. Five to ten minutes before totality came the last focused check: ISO set correctly, the exposure bracket loaded in the camera menu, battery level checked, mount tracking confirmed. Right before C2, the film filter came off, the camera was set to the single exposure planned for the diamond ring — and from that point on, nothing about focus, aperture, zoom, or aim was touched again.
Automation: How the Shots Were Actually Triggered
With only about ninety seconds of totality, there’s simply no time to make manual adjustments mid-sequence — and I wanted to deliberately take my eyes off the viewfinder anyway, to actually experience totality with Gero rather than just watch it through the camera. Both systems ran automated, though in different ways.
The EOS R50 on the Samyang used the camera’s built-in continuous-release function: a sequence stored in the menu that fires through a set number of frames once triggered, with nothing more for me to touch afterward. The EOS R on the apo, on the other hand, was triggered by an external intervalometer from Rollei, which worked through the seven-step bracket automatically. I don’t have the exact figures for repeat count and interval on either system on hand right now — I’ll add those once I’ve checked back against my camera settings.
The Corona Bracket on the EOS R: Seven Steps
The real photographic challenge of a total solar eclipse is the corona’s enormous dynamic range: from the extremely bright chromosphere and prominences at the sun’s edge to the faint outer corona stretching several solar radii, you’re easily looking at ten to twelve stops — well beyond what a single frame can cover. That’s why you need a bracket sequence, which later gets merged into an HDR composite.
Javier, with whom I shared the site, built his composite from a simple three-step bracket — his camera only supports a three-step automatic exposure bracket internally. The Canon EOS R I used on the apo, by contrast, allows up to seven steps in an automatic bracket, and that’s exactly what I used. That wasn’t a deliberate creative choice for smoother transitions — it was simply what the camera was capable of. More steps are generally an advantage for the corona’s dynamic range when the camera can handle them. The cost is time — with only about ninety seconds of totality, there was barely room for more than one or two complete passes through the sequence, which is why the individual steps were spaced roughly two stops apart instead of the finer one-stop steps that would have made sense with more time available.
| Step | Shutter speed | Target |
|---|---|---|
| 1 | 1/2000 s | Diamond ring, innermost chromosphere |
| 2 | 1/500 s | Prominences, near-sun corona |
| 3 | 1/125 s | Inner corona |
| 4 | 1/30 s | Mid corona |
| 5 | 1/8 s | Mid to outer corona |
| 6 | 1/2 s | Outer corona |
| 7 | 2 s | Outermost corona, earthshine on the lunar disc |
ISO stayed fixed at 400, focus was manually locked, and aperture was set by the optics themselves.
The Second Attempt: Samyang and EOS R50
The EOS R50 on the Samyang ran its own, much shorter sequence during totality for the wide-angle context. I tried two different runs there: in one, I bumped the shutter speed mid-sequence to roughly one to two seconds — I still need to double-check the exact value — which came out clearly too bright and overexposed. In the other, the steps sat too close together to add any real value in the composite. The first run is usable in principle, but it doesn’t show any additional detail in the outer corona beyond what the apo images already deliver — possibly because the sun sat only a few degrees above the horizon at the moment of totality, and the haze there cost some additional contrast.
Result and What’s Next
Over the whole afternoon that added up to roughly 70 individual exposures — the partial-phase sequence for the composite, several passes through the seven-step bracket on the EOS R during totality, plus the two test sequences on the EOS R50. Published results so far are exclusively from the apo-and-EOS-R combination; you’ll find those automatically in the “related posts” below this article. The Samyang/EOS R50 shots remain unpublished for now, and for the reasons described above they’ll probably mostly stay that way — though I’ll likely still show one image just for completeness. The full HDR merge from all the EOS R exposures — and what I learned along the way about post-processing a solar eclipse — is a subject of its own.
