Flare depending on strobe model

[Fabian]

Hi everyone,

question to those that have been shooting multiple strobes in wide angle photography.

Do you see a tendency, that some strobe models tend to produce flare more easily on the sides of the image compared to others?

During a recent dive, I compared my strobe positioning (2x Inons Z330, shooting a Canon 8-15mm with 2x TC @16mm) with the positioning of a buddy (2x Seacam Seaflash 160d, shooting a Tokina 10-17 @10mm). I had to pull my strobes significantly further back and I can still see flare. The difference I guess is more curvature in the Inons glass compared to the Seacams, but that is pure speculation. Maybe someone else can share his or hers experience in that regard?
Thanks!

[Barmaglot]

Without diffusers, Z-330s produce a pronounced cross-shape light pattern - https://www.retra-uwt.com/pages/flashgun-light-comparison - it's possible that its horizontal spread is more intense than Seacam's more diffuse circular beam. If I remember correctly, Z-330s have a small rotating hood specifically to control this.

 

Also, I'm guessing it wasn't an apples to apples comparison, as you weren't comparing different strobes on the same rig, but rather two completely different rigs. Flare resistance is heavily affected by glass coatings - what domes were the two of you using? Did either of them have a shade?

[Fabian]

Dang! That picture from the retra page explains a lot! I had the small hood mounted and the rotating shade positioned towards the lens, but I'm probably never going to shoot without diffusors again. I'll have to buy diffusors again (lost one of them), or I move towards other strobes anyways (I'd prefer a bit quicker recycling time, so maybe Backscatter HF-1).

 

Correct, not an apples to apples comparison, it was rig-against-rig, more of an "let's see how you are doing this while underwater".

The dome I've been using is a Zen 230mm, but I have the same issue with the Nauticam 140mm.

 

 

 

[Barmaglot]

To be honest, I don't recall ever having issues with flaring from dome, but I've been shooting with Retra strobes and either SeaFrogs acrylic domes, or AOI UWL-09F wet lens. I can only recall getting flare from sun on the AOI lens.

[Dave_Hicks]

If you are getting flare even from a pulled back position, I am guessing that your strobe power is excessive for the conditions. Strobe power too high, ISO too high, aperture too big, or some combo of these. Get closer and lower the strobe power.

Edited Sunday at 10:40 PM by Dave_Hicks

[Architeuthis]

22 hours ago, Fabian said:

Hi everyone,

question to those that have been shooting multiple strobes in wide angle photography.

Do you see a tendency, that some strobe models tend to produce flare more easily on the sides of the image compared to others?

During a recent dive, I compared my strobe positioning (2x Inons Z330, shooting a Canon 8-15mm with 2x TC @16mm) with the positioning of a buddy (2x Seacam Seaflash 160d, shooting a Tokina 10-17 @10mm). I had to pull my strobes significantly further back and I can still see flare. The difference I guess is more curvature in the Inons glass compared to the Seacams, but that is pure speculation. Maybe someone else can share his or hers experience in that regard?
Thanks!

 

When I switched from Z330 (1st generation with white dome WA diffusers) to Backscatter HF-1 (with 4500K flat diffusers), I clearly noticed that the HF-1s are less prone to "flare" at the edges of the images. I am not sure, but probably the reason is that the HF-1 standard diffusers may provide a less wide beam angle...

 

The physical factors (see below) are different between between different models. In my case every new strobe required learning during the first dives, also how to avoid "flare" in very wide WA, but there was always an improvement at the end (YS-D2 => Z330 => HF-1 in my case)...

 

In general the factors influencing the "flare" are: flash beam angle, beam softness, in/outward aiming of the strobe, distance how far the strobes are pulled back behind handles, angle of view of the lens (most important factor: almost impossible to get "flare" with 17mm rectilinear behind 170mm domeport, even difficult to produce with WACP-C/@28mm, but very easy to get with fisheye 180° diagonal or circular), light shade on the dome (yes/no) and (maybe; I personally do not have experience with circular flash tubes) shape of the flash tube (circular/linear).

ISO, aperture and flash power have same effect on "flare" as on the rest of the flash lightening - therefore I would not use them to control "flare" (maybe "flare" disappers in the EVF when parameters are adjusted, but upon postprocessing the "flare" will reappear without mercy - better eliminate "flare" by other means)...

 

Wolfgang

Edited Monday at 02:22 PM by Architeuthis

[Chris Ross]

It will help to visualise how the plots from the Retra post compare to the field of a fisheye lens.  The often quoted rule of thumb is to separate your strobes the the same distance as the distance to your subject.  With wide beams you may point them out some more.  If you take the zone diagram from the retra link and copy and superimpose them to show the strobe coverage from each strobe, you can then superimpose the frame width of a fisheye lens - assuming about a 135-140° horizontal field. 

 

you will see opposite the strobes the beam is centre plus zone 1 (green brightness)  If you look at the plots of brightness in stops you will see the Seacam is 1.5 stops brighter in Green (zone 1) at constant centre brightness.  So to get the same exposure the Seacam would be turned down a bit on centre brightness compared to the Z330.

 

To me it seems that the more even beam would be less prone to flaring as the strobe is turned down with lower power in the centre compared to the less even beam.  Add to this the tendency towards a cross shaped beam with the Z330 and the fact you are probably aiming the wide beam strobe out some more it gets the bright central beam further away from the dome glass as it leaves the strobes.

 

The other thing to note is the very outer parts of the beam don't contribute much to the image even with the fisheye lens plus the fact that the Zone 3 (magenta) is at least 4 stops less bright than the centre of the beam.

 

the beam widths are:

 

Zone 1:  90°

Zone 2:  108°

Zone 3:  126°

Zone 4:  131°

All based upon the Retra webpage here:

 

https://www.retra-uwt.com/pages/flashgun-light-comparison

[Adventurer]

Hi guys, the RETRA test mentioned is land based, correct?

Same as the private beam shots by Dreifish in this forum.

 

I would like to point out that any strobe that utilizes a dome (such as Seacam, Z330, Marelux) will give you a highly distorted impression of the real beam pattern that will be produced underwater.

 

Once the dome glas is submerged in water it acts like a lens increasing the beam angle and evenly softens the output. -> The quality of light will improve underwater.

 

Just keep that in mind when comparing land based shots.