Poor Man's Wide Angle Lens

Started Dec 18, 2003 | Discussions thread
ForumParentFirstPreviousNextNext unread
Flat view
Ching-Kuang Shene
Veteran MemberPosts: 5,054
Like?
Poor Man's Wide Angle Lens
Dec 18, 2003

As we all know, the APS size sensor makes shooting wide angle a little difficult due to the 1.5X multiplier. The 12-24 DX lens is equivalent to 18-36mm, the 17-35 becomes 25.5-52.5, and the cheaper 18-35 only yields 27-52.5. Moreover, the first two are expensive, and the former is still difficult to find. I believe many may have a good AFD 24mm F2.8 or a cheap Tamron 19-35mm (or a similar one) in hand. Can we use them to go wider? To address this need, we must use front-mounting converters. The traditional SLR type converters, which are mounted between a lens and camera body, only work with the tele side. The other system is the so-called AFOCAL system. An afocal system is front mounting and projects an image onto the camera lens. It is afocal because an afocal system does not have focal points (i.e., parallel incoming light rays become parallel exiting rays, although light bundle size may change). Nowadays, the afocal system is rarely used on SLR/DSLR cameras, but are very popular in consumer level digicams.

There are many front-mounting wide angle converters available. Most of them are cheap and are not of good quality. One of the best and usable ones is the Olympus WCON-08B, a 0.8X wide converter:

This wide angle is one of the sharpest and has a rear thread of 62mm and a large rear glass element. The 62mm thread size is popular amount Nikon lenses, and the large rear glass element reduces possible vignetting. The following shows the WCON-08B mounted on a Nikon AFD 24mm F2.8. The AFD 24mm F2.8 has a 52mm thread, and a 52-62mm step-up ring is needed. The combined focal length on a D100 is 24*1.5*0.8 = 28.8mm which is approximately equal to the widest focal length with a 18-35!

The following shows the result taken with a D100, AFD 24mm F2.4, and Olympus WCON-08B. It is resized and sharpened only.

The following shows the 100% crops of some areas in the above image. Since the original was taken with JPEG FINE without sharpening, the image looks soft. However, some careful sharpening will yield a reasonably sharp result. These crops show the center portion and the right portion. The left edge does show some purple and green chromatic aberration.

The following shows the combo of a Tamron 19-35mm F3.5-4.5 and WCON-08B. The Tamron has a 77mm thread, and a 77-62mm step-down ring is needed. The image shows the use of a 77-72mm step-down and a 72-62mm step-down ring. Of course, the use a single ring is always better than multiple rings. The combined focal length on a D100 is in the range of 19*1.5*0.8 = 22.8mm and 35*1.5*0.8 = 42mm! Now, it is good enough since this combo is almost as wide as a Sigma 15-30 on a D100 (i.e., 22.5-35mm).

The images below were taken at F8 and 1/5 sec (hand-held) in JPEG FINE mode with sharpening. The focal lengths used were 19mm, 24mm, 28mm and 35mm on the Tamron, and are equivalent to 22.8mm, 28.8mm, 33.6mm and 42mm.

The following are 100% crops of the 19mm image. The sharpness can be improved with a careful sharpening. Chromatic aberration, which is shown in the right-most image, seems better than that with the Nikon AFD 24mm F2.8, and appears at different locations. The crop shown is the worst portion. In fact, even at 24mm, this combo has less chromatic aberration along high contrast areas than that of the AFD 24mm F2.8. So, the Tamron 19-35mm and WCON-08B combo appears to perform better.

How much does it cost for any one of these two combos? The Olympus WCON-08B has a street price of $135.00 and can be found on eBay around $100. Since many of us may have already had a AF 24mm F2.8, which is a very popular wide angle lens, getting to 28.8mm with WCON-08B requires only a WCON-08B. A Tamron 19-35 (or a similar one) usually sells for $200 and can be found on eBay about $180 for a new one. Therefore, if you do not want to buy a Sigma 15-30, a Tamron 19-35 plus WCON-08B can do a reasonable job for just $300 plus a couple of step rings.

I did not test the WCON-08B on Nikon's 18-35; but, mounting WCON-08B on AFS 17-35 does cause slight vignetting, although this combo is equivalent to 20.4mm! After cropping, the result may be very close to what we can get with the 19mm end on the Tamron.

I will post more testing images when weather will be getting better. In the foreseeable future (i.e., one or two weeks), my area will be either snowing or cloudy, Feel free to share your thoughts and results as follow-ups. I will probably post my new tests of using WCON-0.7X soon, which can bring the 19-35mm combo to 20mm. Hopefully, vignetting would not be a problem.

CK
http://www.cs.mtu.edu/~shene/DigiCam
Nikon Coolpix 950/990/995/2500/4500 User Guide

ForumParentFirstPreviousNextNext unread
Flat view
Post (hide subjects)Posted by
CK>>New
ForumParentFirstPreviousNextNext unread
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark post MMy threads
Color scheme? Blue / Yellow