View Full Version : Do Step Down Rings = FOV Issues?


rayw
03-27-2011, 10:58 PM
Hi, IT folks

I apologize for laying a question on the board so soon.
I was really hoping to contribute a bit more before asking anything, but here goes...

"Yes" I've already performed and read IT site searches for both step-up rings and adapters and not surprisingly didn't find this subject already addressed in the way I'm going about it.

I have a video camera with a 40.5mm front filter thread.
I would like to buy a wide angle/macro lens, and have two eBay choices:
Both are 0.45 wide angle lenses. Pretty much the same price for either. Off brand names.
Product A requires a step down ring to 37mm mount threads then to 46mm front filter threads.
(Logic suggests the glass is reasonably approximate to that 46mm diameter. I'm new to this, so I'm sensibly guessing).
Product B requires a step up ring to 52mm mount threads then to 67mm front filter threads.

Product A: VCamera @ 40.5mm - 37mm step down - 46mm front lens.
Product B: VCamera @ 40.5mm - 52mm step up - 67mm front lens.

Common sense/logic tells me Product A will create a (potentially) occluding ring in my image/FOV and Product B will reduce or eliminate such a problem.

Bigger glass means more room to not get in the way of itself.

Then I run across the following video and go "Yeah! Yeah! Yeah! THAT'S what I was worried about!"
http://www.youtube.com/watch?v=DFr8c7n_0To&feature=related
The fellow doesn't EXACTLY address the SPECIFIC concern I have in the way I've outlined, but he dances all around it and the problem he runs across (unforgivable blurring on the first lens aside) is EXACTLY what I'm concerned about.

I just didn't want to forget the guy's video as an example before I contributed more around here.
FWIW, I'll try to earn my keep. :)

Thank you very much.


Ray

wheatgrinder
03-28-2011, 12:08 AM
Hey Ray,
dont sweat the noob to the boards factor... youll have plenty of opportunities to help out..


What camera etc are you using? I did a bit of research on finding a good wide angle adapter for my camcorder at the time (canon hfs100) the best reviews all pointed to either the canon branded one, or the raynox HD.. do a search on VIMEO for your camera and potential brand of wide angle adapter and see what comes up.

The cheapies are not going to make you happy, they suck that's why they are cheap... but the raynox aren't that expensive ...

hope this helps..

rayw
03-28-2011, 10:41 AM
Thank you, Wheatgrinder

I'm working off of a Sanyo Xacti HD1010, with 40.5mm filter threads.
The research I've found is not only varied but also... less scientific than I think I'm looking for.

The more I investigate the more I see that I might have actually two, likely three issues to address regarding attachment lenses.

The first issue is a principle:
Will step down rings increase the likelihood of physical occlusion of the field of view?
Common sense says "yes", but experience trumps common sense.
In the illustration I made my points of concern are circled in orange.
Will those points actually cause physical occlusion as seen in that other guy's video.
(Vignetting is a whole other issue).

http://i879.photobucket.com/albums/ab352/rewriteitagain/LensAttachmentIssues.jpg?t=1301326669

The second issue is a principle:
With a larger wide angle lens will the effect I'm actually looking for be negated by the size of the lens itself?
The wide angle effect occurs as the image approaches the glass' outer edge.
If I put a 67mm lens on a camera designed for a 40.5mm attachment will the image just be looking around in the middle of the wide angle glass where there's little "effect" going on?


Third issue is of product quality:
Sakar/Digital Concepts produces an assortment of cheap lens products.
The reviews run the gamut.
http://www.amazon.com/Digital-Concepts-0-45X-Professional-Angle/product-reviews/B001ELQTTA/ref=cm_cr_pr_btm_link_1?ie=UTF8&showViewpoints=0&sortBy=bySubmissionDateDescending
Since some people have no vignetting or distortion while others do I wonder if the issues are actually more related to consumer error related to the first issue I raised above.

Did some of these folks slap on a lens smaller than they should have ("But I used a adapter!") resulting in distorted images?
Or does Sakar/DC produce products of varying qualities depending upon the line or do they just have quality control issues?
"A two-yen lens this week will be fine. Next week... maybe not so great. The week after... 50/50. GL!"

I appreciate your and everyone's consideration of these issues as I go down this first of many rabbit holes.

wheatgrinder
03-28-2011, 11:57 AM
yeah your in a hole. For the price your talking you spend your money and you takes your chances... buy one and see if it works for you.. move on.. you have other bigger issues.. ;)

knightly
03-28-2011, 12:07 PM
Step down will cause corner burn as will filter stacking for exactly the reasons you think.

Step up will help eliminate this for lenses that don't distort the light... Keep in mind, wide angle adapters change the FOV as part of their function, however they happen at the end of the chain generally, so make sure you're accounting for the change in FOV when thinking through your filter diagram.

rayw
03-28-2011, 08:47 PM
Thank you, Wheatgrinder & Knightly

W -
Per your suggestion, I ran across this wide angle review on vimeo and now I'm sold on Raynox products!
http://vimeo.com/3022539
Although I can't imagine the point and purpose of zooming in on a wide angle lens the distortion, blur and haze of the Sakar/DC lens at full zoom is unacceptable.
As you indicated, for literally a few bucks more the Raynox provides a much better alternative.

If you don't mind, is there some fundamental difference between these two Raynox lenses I'm just not seeing?
A: http://cgi.ebay.com/Raynox-DCR-1850-Pro-1-85x-Telephoto-Lens-Black-52mm-/270703240529?pt=Camera_Lenses&hash=item3f072ba551#ht_500wt_922
B: http://cgi.ebay.com/Raynox-DCR-1850-Pro-1-85x-Telephoto-Lens-Silver-52mm-/270703238612?pt=Camera_Lenses&hash=item3f072b9dd4#ht_500wt_922

Their markings in the pictures show they both have the same model number, seller lists them both as being 1.8X magnification, same 52mm mount and 74mm front. Same price.
Cosmetics for marketing?
Year of production?

Thank you.

K -
"Corner burn". I like it. Thank you for confirming what I suspected.


I'm gonna park this link here to refer to later.
http://www.raynox.co.jp/english/video/egvideoindex.htm

wheatgrinder
03-29-2011, 12:31 PM
yeah, but watch out, those videos are for a different camera.

I think the ebay links with the silver one is just the wrong picture. My quick search suggests that itis the 72mm filter thread version. but meh.. youll need to dig deeper..