Jump to content


divegypsy

Member Since 07 Sep 2003
Offline Last Active Today, 04:44 PM
*****

Posts I've Made

In Topic: Nikon 8-15mm in the house!

20 June 2017 - 10:31 PM

Hello Adam,  

 

Most of the thoughts I posted relative to the D800/810/820 and the D500 have relevance to this new fisheye lens as well as other lenses. And were made with the idea that if someone is thinking they might want to buy a D500 to get the "wider" zoom range of 180 degrees to 110 degrees that this lens provides on a DX camera, which is similar to the Tokina 10-17mm lens, that they could get the same zoom range by switching their FX camera to the DX crop mode and lose very little in comparison to a DX only camera. There have been many posts concerning the Tokina 10-17 which is a DX only lens unless you use it with a teleconverter which degrades its image quality. My feeling is that if you shoot a DX camera, and want a similar zoom range, the Nikon lens will provide this with considerably higher image quality. 

 

I did not shoot any pictures underwater at 8mm in the FX mode.  Everything I shot was at the 15mm (full frame fisheye) setting. As I wrote initially, I am not interested in circular fisheye images and I would have needed a zoom gear to make any changes while underwater, which I did not have at that time. My interest in this lens is because I can shoot it behind the wideport at 15mm with no vignetting whereas I cannot do this with the Sigma 15mm. And because it focuses so closely.

 

I had Nikon's own lens shade mounted on the lens when I took the picture of the octopuses that I posted. I shot similar images at f11, f16 and f22 and saw no vignetting in any frame. Since the lens is an internal focus design, that means the angle of coverage of the lens gets slightly wider as you focus closer and closer and the octopuses were only about six inches from the from of the wideport's glass surface.

 

The lens was behind the Seacam wideport with a 20mm extension ring between the wideport and the housing body.  If I get some free time I will take pictures of the housing with the port and extension ring in position as they were during the dive and post them.  I will also post a couple additional pictures that show that whereas the Sigma 15mm lens almost always exhibits some minor vignetting with the wideport, even without any extension ring, the Nikon lens does not.


In Topic: Nikon 8-15mm in the house!

20 June 2017 - 04:10 PM

I saw exactly the same vignetting, caused by the lens shade, when I shot topside pictures.  More extreme vignetting with the camera set to the full FX picture and less when I had my D800 set to the DX crop mode.  If you have an FX camera, like the D800 or D810, you can get the same picture area as Adam did by simply setting the camera to the DX mode.  

 

If you use the D800 or D810 in the DX mode you have a camera that shoots images very similar to the D500. I think it is about 16 Megapixels and has auto-focus spots covering nearly the whole image area. What the D500 offers is faster and possibly more accurate auto-focus, a faster frame rate which is of little use if you are shooting with strobes, and the larger image buffer which again is of little use if you need to wait for strobes to recycle. If Nikon's successor to the D810, D820?, appears with the rumored 46 Mp sensor (an upsized D500 sensor) the D500 will offer very little advantage, except size and weight and price, over the D820 when the D820 is used in the DX mode.  And it will offer more than double the Mp in the FX mode for higher image quality.


In Topic: Nikon 8-15mm in the house!

20 June 2017 - 04:17 AM

I received my Nikon 8-15mm lens about a week ago and have had it in the water once since then.  Because I shoot with a Nikon D800, my interest in this lens is as a close-focusing full frame fisheye lens.  I have very little interest in circular fisheye images.

 

I initially did a few topside shots comparing this lens to my Sigma 15mm f2.8.  My initial impression is that in dim light, the Sigma may pinpoint the focus in the center of the image a little better than does the Nikon lens. Probably due to the fact that the Sigma focuses at f2.8 vs f4.5 on the Nikon lens when set to the 15mm full frame.  But on those same test shots, the sharpness near the edges of the images were consistently better with the Nikon lens.

 

Underwater I have used both the Sigma 15mm and now the Nikon 8-15 behind the Seacam Wideport which has a radius of curvature of about 75mm, meaning that if you had that port as a full hemisphere, the diameter would be about 150mm or about 6 inches. I also own the Seacam 4" fisheye macro port, but pretty much stopped using it because you needed to cut off much of the lens shade on the Sigma 15mm when using this combination and therefore do not have it with me on my current trip.  I feel that cutting back on the Sigma lens shade resulted in too much image degrading flare.

 

With the wideport, I could use the Sigma 15mm with the manufacturer's full shade in place and although I did get slight vignetting at the corners of the image, I feel the image quality was better enough to use the lens this way.  With the Sigma 15mm, I use the wideport directly attached to my Subal housing body.

 

I switched to the Subal housing body for my D800's because I felt Subal gave me a much more complete set of controls to the D800 body functions than did the Seacam housing body and with the help of a good machine shop I was able to modify the port mount on my Subal housings to take my Seacam ports rather than buy a new set of ports.

 

Because the Nikon 8-15mm lens @ 15mm is physically longer than the Sigma 15mm, I am able to shoot the Nikon 8-15mm lens, with its Nikon lens shade mounted, without any vignetting when using the Seacam wideport in combination with a Seacam 20mm extension tube. With a 25mm extension tube, there may be a very slight amount at vignetting, but still far less than with the Sigma 15mm.

 

Below is one of the shots from my only dive so far with the Nikon 8-15mm lens. It shows a pair of small octopuses mating underneath the Edithburgh jetty in South Australia.  The image was shot late in the afternoon at 1/250th at f16 using ISO 3200 on my Nikon D800.

 

Attached File  _F8C8929.jpg   318.54KB   5 downloads

 

When anyone does tests to determine the nodal point of the 8-15mm lens, or any other lens, they should be aware that the nodal point of the lens lens can change with both the zoom setting and the focus point of the lens.  I found quite large differences when I did a series of tests on Nikon's 24-70mm f2.8 several years ago. Using the manufacturer's given nodal point is also likely to be at least slightly inaccurate for underwater use because the manufacturer's nodal points are given for lenses focused at infinity rather than at the close distances the lens is likely to focus at when used behind a dome port. 


In Topic: Housing buttons that stick

24 December 2016 - 12:47 AM

Dear Vladimir,

As I have mentioned, I have three ND800 housings, two of which were purchased directly from Subal. Mr. Harold Karl can verify this. He can also verify that I had all three of the backs of my ND800 housings painted black, by Subal, to reduce reflections off the housing back when viewing the LCD screen under high ambient light conditions. Shortly after receiving my housings, I started having problems with sticking buttons, and communicated directly to Mr. Karl about this. I also mentioned to Mr. Karl that I had seen posts on WetPixel by other ND800 users having this same push button problem. I received no response from Subal on this. I use the same D800 camera body in each of my ND800 housings. I take two housings with me on all my trips so that if one is lost by the airlines or in an accident, I do not lose the ability to take underwater pictures. The third housing sits at home ready to replace one that might be lost.

I can understand that Subal may not have had very many complaints about the sticking buttons because many users probably go on dive trips only two or three times each year. And if a button sticks, they might logically think it is due to lack of use, and say nothing. But right here you have four ND800 users who have had this problem. Elmer, Tim, myself and my friend Don. This is not an insignificant number.

Elmer has said that Reef Photo installed stronger replacement springs into his housing which helped alleviate his problem. Tim had to shorten the internal rod that made contact with his camera button. My friend Don Howie sent his housing back to Subal at considerable expense with no improvement and was eventually sent stronger springs and different washers, which he had to have installed. You also mention replacement arm levers.

What do I need to do to acquire some stronger springs (24 stronger springs - eight for each of my three ND800 housings) and three sets of replacement levers with wider contact parts to try to fix the problem. It is only the five push buttons for the auto-focus point selector (which I think you refer to as a joystick?) that I would need new levers for. Shipping my three housings to Subal in Austria is not a reasonable solution as that would cost hundreds of dollars per housing to fix a problem that has existed since the day I received the housings.

I have reasonable mechanical skills and have a friend with machine shop tools such as a lathe and milling machine. So installation and adjustment of the new parts should not be a problem if you send clear instructions on how to do it.

Please let me know what you and Subal are willing to do to help me solve this problem.

Thank you,

Fred

In Topic: Recommended maintenance schedule for Subal housings?

20 December 2016 - 04:12 PM

Vladimir,

 

Would you please look at the topic about sticking push-buttons.  In particular on Subal housings.  Is Subal willing to send replacement springs to the Subal ND800 purchasers who are having trouble with their push-buttons?  As I am.  How can I get the "stronger springs" that one of the Subal users says Reef Photo installed in his housing to reduce this problem?

 

Fred