[camerasup]

A quick refresher... but which offer better functionality? I currently have a front one that I'm afraid of its sheer weight is at a disadvantage. I will not mount it on any front plastic threads.

I'm in the market for a rear converter soon. I will soon test for myself.

[UncleVanya]

The only serious TC's I have seen have all been rear. That doesn't mean anything really - just an observation.

[vonBaloney]

Front wide-angle adapters can be decent (they can be bad also), but front magnifying TCs are usually problematic (more problematic than rear) -- the same adapter will work OK on one lens and terrible on another. Almost any front TCs you'd find (other than Raynox macro attachments) will be designed as add-ons for either video cameras or p&s/bridge cameras. In short, I would not bother with them.

[promacjoe]

Basically, I can only see two advantages to a front tele-converter.

1: you're not putting anything in between the electronics of the camera and lens.

2: there is a potential, depending on the lens used, to maintain the light capacity of the lens. But this is not guaranteed, hence the word potential. On certain lenses light capacity may decrease significantly if not more than a standard tele-converter.

Disadvantages include, but are not limited to,

1: as others have said, image quality may suffer greatly.

2: this is a heavy mass placed on the end of your lens. Any lens that rotates during autofocus can potentially have problems. this mass could damage the autofocus system within your lens/camera.

3: your autofocus may not even work with these lenses.

4: Even if the autofocus can handle the mass, that same mass can move the front element out of alignment with the other lenses and cause distortion.

5: SR will not see the new focal length. So SR should be turned off.

6: the metadata will not be correct. There is no way for the camera to ascertain the true focal length being used. Note: there is no guarantee that a standard tele-converter will compensate for the difference in focal length

For manual focus lenses however the front mount tele-converter can work, but some of the same problems will still exist. I do not recommend them.

[stevebrot]

In short, I would not bother with them.

What he said...

With the exception of the better auxiliary macro lenses (e.g. Raynox) and some wide-angle types, the optical quality of auxiliary lenses is inferior.

Steve

[dms]

I am a bit confused by the term "front teleconverter." Is there such a named device? I presume you mean an add on lens (diopter) that modifies the existing lens optical formula. I believe this is fundamentally different than a rear teleconverter--that essentially acts only as as a magnifier, enlarging the image already formed by the lens.

[promacjoe]

A diopter filter increases the magnification of the lens. They are used for macro photography. but it does so at a cost. It reduces the focusing distance from the subject to the camera lens, so that it will no longer focus to infinity. It's like putting on reading glasses for your camera. A front mount tele-converter/tele-reducer also changes the focal length respectively, but it does so in a manner that maintains the range of focus of the lens. a diopter filter is about the same size as a standard filter. a front mount tele-converter is very large and very heavy, Normally much larger than the diameter of the original lens. Vivitar makes them as well as several other companies. they are not new, they were used in the early days of 35mm cameras without interchangeable lenses. And I'm sure other types of cameras use them as well.

[camerasup]

thanks you guys sure know your stuff. I will post a pic with more details describing this old no name chunk of glass. It may play a vital role with either my Pentax 135mm or M 200mm soon.

[camerasup]

The only serious TC's I have seen have all been rear. That doesn't mean anything really - just an observation.

So which one do you recommend? Would an old Jc Penny TC be any good?

[UncleVanya]

So which one do you recommend? Would an old Jc Penny TC be any good?

I'm no expert - the old TC's I used to use were mostly junk. They worked but when you are poor and you have no choice you don't complain.
Some newer more expensive TC's are really something special from what I see. The main thing would be to determine your feature set.

"A" type contacts?
Auto Focus? Screw Drive only or SDM/DC compatible?
Long or short lens focal length may also matter - there are some TC's optimized for use with one or the other.

[reeftool]

So which one do you recommend? Would an old Jc Penny TC be any good?

I have a couple of old JC Penny lenses that are OK stopped down. The old dept. store brands like Pennys and Kmart's Focal brand were made by various lens builders and some were decent and others were junk. I have an old Vivitar TC in M42 mount and it does a pretty good on on my Takumar 200/4. It was really cheap and worth taking the risk. The same can be said for old K mount TCs. If they're cheap enough, they may work fine and you got a deal and if they're junk, you can always take the glass out and you have an extension tube for macros.

[Scobra]

The Ricoh GX100 and GX200 compacts had a front-mounted 1.88x teleconverter optional accessory called the TC-1.
The GX200 was a premium compact for its day and so was the teleconverter, which now changes hands for big bucks on eBay.
I used to own this combo and made many great panoramas with it.

It was a "matched" teleconverter designed from the beginning to complement the GX200's limited zoom, and the relatively small sensor of the GX200 probably means it is of limited use on other, larger sensor camera bodies.

Even teleconverters made for SLRs and DSLRs, if they are old and cheap, the lens resolution would be defined by their price: you get what you pay for.

Review of the TC-1 with test shots here: GX200 & TC1 (135mm tele extension lens) | GR User Forum

---------- Post added 2nd Oct 2023 at 03:56 AM ----------

ps interesting review of 8 different front-mounted teleconverters here, including vignetting examples:
Some High Quality Telephoto Converter Lenses

[zapp]

You should not put any heavy adapters in the front filter mount. Tele converters, ring flashes, even heavy filters ... all pull on lens tube and cause slight deformation. Depending on the lens, the AF engine has to move more weight as well. Front converters only make sense for cameras where you cannot remove the lens - otherwise, a generic front converter is inferior in quality compared to a dedicated rear moiunt converter. Rear mount with contacts allows to pass on focal length and focus distance thus exif information is more complete and SR works better.
Converters are tempting, they can be fun to use, cheap ones are not for serious work.