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Undertow

Member Since 05 Dec 2006
Offline Last Active Jul 14 2018 11:31 AM
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Posts I've Made

In Topic: Tamron 15-30 f2.8 for underwater photo?

28 May 2018 - 03:22 PM

No idea but heard Tamron's have poor quality control vs other brands (some might be soft). Worth checking with your housing manufacturer if they've tested the lens and figured the proper size dome extension ring. Otherwise doing the measurements yourself for an extension would be challenging. Lenses need to be carefully aligned with domes. 

 

If it has a built in hood, it may not fit in a dome. Though all rectilinear super-wide lenses really should be used with large 9"/230mm domes. 

 

Also, as we've seen with Nikon's 14-24mm vs 16-35mm, lenses considered 'better' above water may not be so underwater. 

 

Cheers,

 

Chris


In Topic: What is wrong with my settings (Sony rx100iv )

06 May 2018 - 01:37 PM

Have to disagree with Mike and undertow.  Your shutter speed is slow enough for the strobe to fill the scene. I would tend to agree if you had a shutter speed that was faster than your strobe (ie 1/250 or faster) but slow is not usually a problem.  See my photo below with same shutter speed both upclose and wide angle (shutter speed 1/100-1/160).  I do agree that you should shoot in M mode. 

 

I think you've misunderstood Mike and I. What we said has nothing to do with the strobe syncing with the camera (i.e. having too fast a shutter speed).

 

This is basic exposure stuff. When using strobes, you're mixing 2 forms of light:

 

1. Strobe Light

- strobe exposure determined by combination of strobe power and aperture

 

2. Ambient light from the sun

- ambient exposure determined by combination of shutter speed and aperture

 

In your excellent images, kdgonzalez, if you erased the strobe light (if your strobe didn't fire), they would be very dark, very underexposed. The eel image would likely be black. That means you have a dark ambient exposure. The issue with the original poster's images was that the ambient exposure was way too bright to begin with. 

 

There's no room for disagreement here, this is 100% true. 


In Topic: Port Glass "Cloudiness"

30 April 2018 - 10:09 AM

So I think I can claim tentative success with this after some research and choosing Mothers Chrome Polish.

 

3 x 15min applications later and all of this etched blotchiness is finally gone. Did put some proper effort into this, scrubbing quite vigorously. 

 

I've had this dome (Aquatica Megadome) for about 10yrs and was pretty bad about giving it proper care. It would sit salty on the boat in the sun for hours on end on a regular basis. I never wiped it dry after rinsing etc. 

 

In the second photo, you can see the leftover blotchiness right by the hotspot. This is because I didn't scrub properly all the way to the tape (used to protect the o-ring). I might try another application to get a bit further down.

 

The rest of the dome looks fantastic. 

 

However my secondary issue is the optical coating on the inside is wearing off (you can barely see as 'streaks' just to the left of the visible blotchiness). So I have to decide if I do an application on the inside to clear it. Not sure its necessary though. 

 

Attached File  _DSC0382.jpg   127.39KB   19 downloads

 

Attached File  IMG_7128.jpg   89.17KB   19 downloads

 

Cheers,

 

Chris


In Topic: What is wrong with my settings (Sony rx100iv )

30 April 2018 - 09:41 AM

Mike is right. This is the second time recently I've seen the same question asked and people keep talking about the strobe.

 

(Yes you may find strobe positioning when over a bright bottom is something to work on but that's completely secondary to the main issue here.)

 

Your ambient (non-strobe) exposure is way too bright. 


In Topic: New TSA rules and underwater strobes

27 April 2018 - 07:58 AM

Recently flew out of LAX (Los Angeles) and TSA was telling everyone to take cameras out of their bags. When I asked about additional lenses they said to leave them in the bag. Didn't have strobes on me but got the impression I wouldn't need to remove them. Sounded like a camera-specific new thing. 

 

I also flew through Reno on the same trip and nothing about cameras.