Ikelite port Vignetting problem

I´m experiencing some strong Vignetting problem with this lens and Ike port 5503.80 on 17mm to 19mm, I tried in a 5503.55 and 5503.50 and in both, it bumps the port, so been this the ike recommend port for this lens, i have a couple of solutions but none satisfy me...

I´M PLACING THE PORT AS IS RECOMMEND IT IN THE MANUAL FOR IKELITE FOR LENS WIDER THAN 20mm.

1) remove the shade of the port and shoot like that (obvious solution but i´m trying to figure something else...)

2) sand paper the shade on the sides and on the cut outs (i don´t know...)

I don't know this lens or port combination. However, one thing to check first is if you have the dome shade in the proper orientation. The shade is not circular and should be oriented so that the widest part is horizontal like the viewfinder.

If that's not the problem then I would just dremmel tool the shade until it doesn't vingette. This won't hurt anything. The most important thing the shade does is protect the port. This is better than removing it. If you don't like the results you can always buy a new shade for little $.

Vignetting should be expected with #5503.80 and that lens. #5503.80 is nearly 2" too long. I doubt that removing the shade would fix the problem.

Sigma claims the maximum length of the 17-70 is 3.2" so the lens should fit fine in #5503.50 (for lenses less than 4" ). So if #5503.50 does not work, something funny is going on.

What do you mean by "bumps the port" ? What part of the lens bumps what part of the port? Can you take a ruler and measure the maximum amount the lens extends from the camera body?

Well I think the nodal point of the lens wrt the dome is also important for it it fit optically in the port. I'll leave it up to the optics types to figure this one out. Its not in the Ikelite port chart.

Before you dremmel it make sure you are happy with your results optically, corners, center everywhere.

What do you mean by "bumps the port" ? What part of the lens bumps what part of the port?

The front of the lens bumps the inside front of the port, letting it extend only to 40mm (in 5503.50), the only port that allows it to fully extend is this one (5503.80).

Optically everything seems to be right. My concern is the vignetting, so dremmel the shade sounds right... besides this solution anyone think in soemthing else?

Would you please measure the length of the lens? I am curious if the manufacturs dimensions are wrong.

And about how much longer would 5503.50 or 5503.55 need to be to make it work? Measure how much the lens grows from the point it hits the front of the dome. Ikelite can make a dome that is inbetween 5503.55 and 5503.8.

If you can find one to try, I would also recomend you try the 8" dome. It may solve your problems.

This lens fully extended is close to 4.9", the 3.2" dimension is fully retracted... In the Ike port chart, this lens is listed in canon, and recommended to use 5503.80 but in the port instructions clearly specify that in lens wider than 20mm the shade may have to be removed to avoid vignetting...

I think maybe is the standard form that ike made the same shade to fit all ports... So not to blame both manufacturers, but different types of shades (better looking shades) can solve many problems on ike ports, even with the 8"... I don´t know, but besides this, the ike super dome is the less appealing of all domes (compare to super dome used on sea&sea, subal´s or Athena´s... and i think is because the size and the lack of shade, wich give protection and look a lot better.) ( I know this has been discussed here before...)

Just a customer opinion...

Actually I like the 8" dome a lot. Its better constructed than the standard 6" domes. I'm sure Ikelite will develop a dome shade for this eventually.

The shade for the 8" dome port is already in the works. I don't have any more information right now, but I can say it is being developed.