[Filter Test] AndreaU, BaaderU, PrecisionU with UV-Flash & S8612

[Andrea B.]

EDITOR'S NOTE:  10 Dec 2021

This earlier version of the AndreaU UV-pass filter is no longer made.

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Experiment: Photograph a dandelion in sunlight using the BaaderU, AndreaU and PrecisionU UV-pass filters

1) with and without additional IR-blocking, and

2) with and without boosting UV via UV-flash.

 

Equipment: D600BB + UV-Nikkor 105/4.5

UV-Flash: Nikon SB-14 modification

IR-Blocker: S8612 (1.75mm)

Exposure: f/8 @ ISO-200 with varying exposure times

 

Photo Grid

Row 1: No IR-Blocker

Row 2: With IR-Blocker

Colm1: Sunlight

Colm2: Sunlight + UV-Flash

 

Raw composites were made in Raw Digger.

To even out slight exposure differences the histogram white point was adjusted on each raw composite.

 

Proofs were made in Capture NX2.

White balance was made on the same area in each foto.

To even out slight exposure differences the histogram white point was adjusted on each raw composite.

Some highlight recovery was performed.

Some sharpening was added.

 

Conclusions:

 

1) Adding artificial UV illumination to sunlight via the SB-14-mod boosted the UV response in all cases and resulted in shorter exposure times by approximately 5 stops. No surprise there.

 

2) Adding artificial UV illumination to sunlight via the SB-14-mod UV-flash (or other flashes or lamps) may mitigate the need for additional IR-blocking on a UV-pass filter. The PrecisionU in sunlight plus SB-14 showed an improved UV response.

 

3) Adding artificial UV illumination to sunlight via the SB-14-mod may change the raw RGB response of a UV-pass filter. The AndreaU in sunlight plus SB-14 showed a slightly altered raw response.

 

3) Adding additional IR-blocking via the 1.75mm S8612 IR-blocker increased exposure times between 2/3 - 5/3 stops. No surprise there.

 

4) Adding additional IR-blocking via the 1.75mm S8612 IR-blocker may boost the UV response of a UV-pass filter. The PrecisionU plus the S8612 showed an improved UV response. The BaaderU and the AndreaU did not seem to benefit from the addition of the S8612.

 

 

BaaderU Raw Composites

 

BaaderU Proofs

 

 

AndreaU Raw Composites

 

AndreaU Proofs

 

 

PrecisionU Raw Composites

When shooting with the PrecisionU using the UV-flash, the shooting conditions began to change. So the set of exposure times for the two UV-flash fotos is anomalous and no judgement should be made about it.

 

PrecisionU Proofs

 

 

6-plex of UV-Flash Results

I typically shoot in sunlight with an SB-14-mod to shorten exposure times. Here is a summary of the UV-flash results - raw composites in first row and proofs in second row.

[Andrea B.]

Gotta have some fun.

[colinbm]

Good comparisons Andrea

It seems to my eye that for all except the PrecisionU, that the, filter only in sunlight, gave the best results.

Col

[Andrea B.]

It's difficult to say for sure, Col, what is the 'best' result because of variance in exposures? For example, when using a UV-flash, the UV-signature appearance is somewhat dependent on how close we hold the UV-flash to the flower (or other subject). And there are variations in sunlight to consider also. Even when the sky is cloudless, the atmosphere is always performing its little tricks. While we cannot "flash away" a UV-absorbing area (as long as we have not overexposed it, of course), there will always be some minor contrast variations which we probably have to disregard in a non-studio series like this. The only thing we can look for in such experiments is evidence of IR contamination which appears as the typical 'washed out' region in an area which we know should be much more UV-absorbing.

 

But I welcome any debate or comments on anything I just said there. It will help me to improve future test results.

[nfoto]

A UV-capable flash tends to bring forth fine detail much better than direct sun light. However, there is a balance to be struck here as most detail is shown when light field is very flat and grazing, which also makes contrasts heavier. This kind of light set up, common in the '50s and '60s, is unpleasantly harsh for our current-day taste.

 

In a studio setting, I find 2 strobes arranged at approx. 45 degrees angle of incidence and pointing slight down to be the best compromise. As the flash heads are huge compared to most subjects, you avoid very flat lighting yet preserve directionality so as to bring out extra detail. Shadows are also nicely filled in.

[colinbm]

Thanks Andrea

When you say, UV-capable flash, I understand that to mean, the straw coloured UV filter on the tube has been removed ?

Col

[nfoto]

I tend to equate "UV-capable flash" with "flash with uncoated Xenon tube", which of course is a very strict and limited view. But all flashes used by me are of this kind: either the massive Broncolor studio flashes, or the much smaller and field-suitable SB-140 ones.

 

I'm sure you can get good UV captures with presumably older flash units with or without coating removed. But nothing beats a special flash if you need the power.

[colinbm]

Thanks Bjorn

Col