Inon UWL-100 off center out of focus and weird streaking look

[DazedAndConfuzed]

Hi,

I just started using the Inon UWL-100 on my old Oly C-5050 / PT-015 housing. In wide angle shots, it looks great (besides the barrel distortion), but in closeup shots, off center gets extremely soft, along what looks like streaking blur of the image (like when you zoom in during mid-shutter).

Most of the shots are when I zoom in the lens to full zoom (105mm equiv) and up close. So it can't be anything related to the extreme wide angle-ness of the UWL-100. (I remember seeing that kind of blurriness when I use to mount my lens backward on my SLR, but that was just experimenting and wasn't expecting to get perfect results).

I read something in a prior post about it, but there was no clear conclusion. It can't be depth of field since the background in the center is sharper than the focused subject at off-center.

When I shoot with just my camera's lens, I never got anything that resembled anything like this.

It looks something like these pictures (not mine):

 

[Interceptor121]

Hi Lwamg
You are not supposed to zoom with the UWL-100 if at widest zoom the subject is too small you need to remove the lens
Wide angle wet lens such as this one are not meant to zoom in, you zoom with your fins or take the lens off

 

[DazedAndConfuzed]

I am zooming in to get a bigger image. Most of the shots I took when fully zoomed in are when I am only 3-6 inches from the subject and zooming in only increases its size in the frame.

I tried initially shooting with my camera lens almost fully zoomed out and as a result bumped into the rock the subject was resting on once or twice, without getting the subject big enough, thus the need to zoom in.

I did take the lens off once or twice when I needed more 'zoom', but the task of screwing it off is a tedious effort where I might have the chance of dropping the lens, so I kept the lens on most of the time. Plus with the lens on, I could focus much closer than w/o it on.


Is the aberration a result of the close focus or the zooming in? I don't know how it could be the zooming in since all I am doing is discarding the light coming out of the lens that were from the more extreme coverage angle.

 

[DazedAndConfuzed]

I think the issue is that the UWL-100 focuses its image on a slightly curved focal plane instead of a fully flat one. When the zoom lens is fully zoomed out, the dept of field from wide lens is able to fully compensate for the slight difference in focal point between the center and side of the image. But when the lens is fully zoomed in, along with focusing so close to a subject, the depth of field (as seen by the camera's lens) become extremely shallow (even if the image projected by the UWL-100 is not that shallow), thus things off-centered becomes more out of focus. The streaky nature of the lines also looks like a curved plane, with elongation of the image.

I thougth 5 lens elements with aspherical element will resolve any of these problems, but I guess only to the point where it can be corrected by the camera lens.

 

[Interceptor121]

This is not an issue with this lens only every wide angle or dome underwater will get blurry when you zoom as they are not designed to do that

I recommend you get a lens caddy and get into the idea of taking the lens off when you need to do close up work

 

[DazedAndConfuzed]

I presumed a $400 lens would be able to project a flat focal plane, but I guess it is an issue with general wide angle adapter lens that has to be placed in front of a existing lens, having to be made to work for all cameras' lens and distance to them.

I could try shooting zoomed in with lens stepped down to f11 or more.

If the outcome is acceptable, then I could then have a different my-mode on my camera, one with my lens at wide angle and at shutter priority mode of 1/400 sec for fast flash sync and let the camera decide on f-stop, and another one with my lens fully zoomed in and in manual mode of 1/400 sec and lens stepped down as much as possible.

Thinking of lens caddy, although this lens lets me get much closer than my camera's lens. Maybe I should use diopter lens instead of this for macro shots.

 

[Nemrod]

Hi,

I just started using the Inon UWL-100 on my old Oly C-5050 / PT-015 housing. In wide angle shots, it looks great (besides the barrel distortion), but in closeup shots, off center gets extremely soft, along what looks like streaking blur of the image (like when you zoom in during mid-shutter).

Most of the shots are when I zoom in the lens to full zoom (105mm equiv) and up close. So it can't be anything related to the extreme wide angle-ness of the UWL-100.

You CANNOT zoom in with the accessory lens. Sure, a step or two but not full zoom or even close to full zoom. I imagine the lens is slightly too far away and this coupled with your "full" zooming is definitely going to cause the severe distortion EXACTLY like you are seeing. This is even covered somewhat in the Inon catalog.

Why put a wide angle lens on and then zoom? Just take it off.

N

 

[DazedAndConfuzed]

You CANNOT zoom in with the accessory lens. Sure, a step or two but not full zoom or even close to full zoom. I imagine the lens is slightly too far away and this coupled with your "full" zooming is definitely going to cause the severe distortion EXACTLY like you are seeing. This is even covered somewhat in the Inon catalog.

Why put a wide angle lens on and then zoom? Just take it off.

N

I thought with its 0.6x magnification factor, my lens would effectively change from 35-105mm to 21-63mm. Didn't know it will only be a 21mm lens. I keep the WA lens on bcuz it also allows me to focus much closer than my current lens. I could try to get macro shots fully zoomed out, but when I zoom in, I can get a 3x bigger image. Otherwise, I would have to get so close to the subject that the lens is almost touching it. That is almost impossible unless I am taking picture of slugs.

Alternative is to carry a diopter closeup lens in addition to WA lens and change between those 2.

 

[Interceptor121]

That is exactly what you have to do. Carry a dual lens caddy and both a wide lens and a diopter or two the Inon UCL-165AD will do the job for yours and enable you to shoot larger than life from 4 inches distance underwater

 

[Nemrod]

I thought with its 0.6x magnification factor, my lens would effectively change from 35-105mm to 21-63mm. Didn't know it will only be a 21mm lens. I keep the WA lens on bcuz it also allows me to focus much closer than my current lens. I could try to get macro shots fully zoomed out, but when I zoom in, I can get a 3x bigger image. Otherwise, I would have to get so close to the subject that the lens is almost touching it. That is almost impossible unless I am taking picture of slugs.

Alternative is to carry a diopter closeup lens in addition to WA lens and change between those 2.

Sorry, if wishes were horses then beggars would ride, sorry, not going to work. You cannot zoom to the extent you are attempting to do without severe distortion. No, you cannot turn a wide angle lens into a zoom telephoto.

Yes, to do wide angle close focus, the lens must nearly touch the subject. Repeat, you cannot stand off and zoom in. You either will need to remove the wide angle lens or move close even if it means nearly touching the subject.

Good luck.

N