"patton paul" <ppatton@ux1.cso.uiuc.edu> wrote in message

news:Pine.GSO.4.31.0308191047090.10758-100000@staff1.cso.uiuc.edu...

> I have a Nikon N90s camera and do lots of photos of insects and other

> small animals, lately mostly butterflies and dragonflies. I have a Nikon

> AF 70-300mm zoom lens and a Nikon 28-105 mm zoom. I mostly use the

> 70-300mm lens for close ups, in combination with Kenko 36, 20, or 12 mm

> extension tubes, or Nikon 5T or 6T closeup lenses. I'm thinking of adding

> a teleconverter to my collection of accessories, since this would allow me

> to be at a greater distance from the butterfly, but still have it fill the

> frame. I have two decisions to make. First, I need to decide whether to

> get a 1.4x or 2x teleconverter, and I need to decide what brand to buy.

> Unfortunately, Nikon doesn't seem to make an autofocus teleconverter that

> is compatible with my camera. I'm seriously considering Tamron

> teleconverters, which are available at a local photography shop with the

> 1.4x for $139.00 and the 2x for $179.00. Does anyone have an opinion on

> the quality of Tamron lenses, or have any suggestions about what other

> brands I should consider? With the 1.4x converter I would lose one stop

> worth of light, and with the 2x converter two stops. Loss of light may be

> an important consideration for closeup photography, because I usually use

> f16

> or greater to maximize depth of field. If I use film with ISO greater

> than 200 to compensate for loss of light, will I have problems with

> graininess in enlargements to 8x10 or larger (I use slide film and have a

> Polaroid SprintScan 4000 slide scanner. With my Epson 1270 printer I can

> print digital enlargements up to 13x17, and so would be concerned about

> preserving image quality up to this size, although I more frequently print

> 8x10s). Comments on this issue of 1.4x vs. 2x and the consequences of

> light loss would be highly welcome, especially from people who have tried

> butterfly photography with similar lens combinations. Thanks.

If the magnification is very high, AF does not work very well (what is in

focus is selective due to DOF issues, and unless you like the sharp part

always near the center, AF will not do...

For me, converters are VERY useful for macro work, but only

because I use TTL flash (one placed at the end of the lens, pointed

at the subject, and placed close to the subject provides high effective

shutter speeed, the gives the ability to use very small effective stops,

permits using the better slow films, and provides surprisingly soft

and natural-looking lighting). See www.David-Ruether-Photography.com/phun.html,

"Bugs" (the higher-magnification images are flash). Tubes often

provide poor optical results with zooms unless small stops are used,

as do 2X converters and simple close-up lenses - but at small stops

I may combine tubes, achromats, and tele-converters for high-magnification

images that are also sharp. (This does not directly answer your questions,

but may give you the info needed...;-) BTW, I do not use the

N90/N70 due to their relatively soft-looking viewing screens - the

F3/N8008/F100 viewfinders are noticeably sharper and easier

to use for MF...

--

David Ruether

d_ruether@hotmail.com

http://www.David-Ruether-Photography.com