[Mike.P®]

I have just won a Sigma 70-200mm f2.8 EX APO (Non DG, Non Macro, Non HSM) on Ebay for a reasonable price (for us UK buyers anyway) and would like to know if the 2X teleconverter degrades the image quality by much as if it does then I may as well keep my Sigma 135-400mm DG APO for a while instead of buying the converter.
I notice the converter is DG EX so is that going to cause any problems with a non DG lens?
I also have a Tamron 1.4x MC4 teleconverter so was wondering if anyone had tried this combo?

Finally, anyone got any pics taken with K10D and any one of these combinations?

Thanks.

[HermanLee]

I dunno with Sigma 70-200, but I tried my FA*80-200mm with Tamron 1.4X TC on my K100D.
The quality seems to degrade a bit but not much. Maybe if I pixel peep it will show more differences. Otherwise, it's good enough for me.

[Ben_Edict]

I have the Sigma 70-200 and use it happily with the Sigma 1.4x Apo tc. My copy of the Apo 2x tc seems to be a bit poor, because I see a clear loss in IQ, when using it, whereas the 1.4x Apo tc delivers first rate results. This is the reason, why I finally added a Bigma to my collection, which at 400mm (and even beyond) has a very good IQ.

But Lowell posted some sample images of his Sigma 70-200/2.8 combined with the Apo 2x tc - and these were very sharp and had good contrast. If you search the forum, you will sure find his images. If "your" copy of the 2x tc is as good, you won't need your 135-400 anymore...

Ben

[Miserere]

I notice the converter is DG EX so is that going to cause any problems with a non DG lens?

Mike,

DG simply means that the rear element of the lens (the part facing the CCD) has been coated to avoid light reflected from the CCD to bounce off the element and go back to the CCD. Using a non-DG lens with a DG TC, if anything, is a good thing as the rearmost element of your lens combo now has a DG coating

I am also eyeing this Sigma lens and might decide to buy it if the seller gives me a good price. I would like to hear from you what you think of it. I know the EX APO DG Macro version has a great reputation, but I'm not sure about the EX APO. I'll go read the reviews here, but they are mixed amongst different versions.

---

Last edited by Miserere; 11-05-2008 at 04:58 PM.

[Lowell Goudge]

I have the Sigma 70-200 and use it happily with the Sigma 1.4x Apo tc. My copy of the Apo 2x tc seems to be a bit poor, because I see a clear loss in IQ, when using it, whereas the 1.4x Apo tc delivers first rate results. This is the reason, why I finally added a Bigma to my collection, which at 400mm (and even beyond) has a very good IQ.

But Lowell posted some sample images of his Sigma 70-200/2.8 combined with the Apo 2x tc - and these were very sharp and had good contrast. If you search the forum, you will sure find his images. If "your" copy of the 2x tc is as good, you won't need your 135-400 anymore...

Ben

Ben

I'll save the trouble

https://www.pentaxforums.com/forums/187646-post19.html
https://www.pentaxforums.com/forums/208249-post1.html

Note, my 1.4X ia an APO EX (non DG) my 2X is an APO EX DG

This really tells the difference in purchase date more than anything.,

I bought the 1.4x with the lens in early 2004, the 2x this spring.

[palmor]

I have the Non DG Sigma lens with the Non DG 2xTC and it is a great combo. This question comes up every once and a while... I think Lowell and I are the two biggest users of this combo

I have more examples in the Birds gallery of my pbase account... mostly at the top of the gallery (I now use a 400mm prime instead of that combo).


John



https://www.pentaxforums.com/forums/183940-post4.html
https://www.pentaxforums.com/forums/post-your-photos/3555-eagles-snowy-owl.html
https://www.pentaxforums.com/forums/post-your-photos/4039-short-eared-owl.html

[Lowell Goudge]

I forgot to mention one point, very very important.

The K10D has a metering defficiency, that causes over exposure by about 1 stop with the 1.4 x TC and 1 1.3 stops with the 2x TC,

It has to do with the focusing screen, and the way light passes from the focusing screen and metering system as a function of actual F stop of the lens. As the present teleconverter does not modify any lens information going to the camera from the lens, it reports a maximum apature of F2.8 as opposed to F5.6 when the TC is attached. The K10D needs to know the actual apature to correct for the focusing screen, and since it does not get the apature modified, the metering is off.

This is easily corrected for all automatic modes, but on the K10D you cannot enter an esposure compensation in manual mode like you could on the *istD.

ALso, but not as important, since the lens does not modify the focal length reported by the lens, shake reduction is not optimal.

[palmor]

I forgot to mention one point, very very important.

The K10D has a metering defficiency, that causes over exposure by about 1 stop with the 1.4 x TC and 1 1.3 stops with the 2x TC,

And I thought it was just me that had that problem with this setup, glad to know it isn't just me . I always dial in a -1 when using the lens and 2xTC combo.


John

[Lowell Goudge]

And I thought it was just me that had that problem with this setup, glad to know it isn't just me . I always dial in a -1 when using the lens and 2xTC combo.


John

John

If you want to see the whole story look at the following.

think about the difference between F2.8 and F5.6 and that each stop is 45 in the middle of the histogram.

This is probably why many arn't sold on the combo, they have not tested it to know how it really works. I actually test all my lenses against the camera's metering, for both bodies so I know what to really expect/

https://www.pentaxforums.com/forums/241716-post69.html

[nobbsie]

I have the same version of the Sigma and I've used it with the Kenko MC7 2xTC with good results.

All of the images in this gallery after the first three were shot with that combo:

Amberley Air Show - 2008 Photo Gallery by nobbsie at pbase.com

IMO IQ loss is quite difficult to notice if you stop down to around f/4.5, the loss of light will probably have more impact on your images than the loss of IQ.

[Mike.P®]

Ok, cheers for all the feedback, I think I will order myself a 2X Sigma teleconverter and try it with that. If its as good (not hard) or better (still not hard) than my 135-400mm DG APO then I can get rid of that and put the proceeds towards my next want (DA*300mm).

Thanks again.

[Trev campbell]

Hi Guys, I have a Sigma F2.8 APO DG II 70-200mm HSM lens and it's been fantastic, but I wanted a little more reach on the lens. I got a Teleplus Pz-AF 2x MC7 off ebay. It has all the correct connections for the HSM but when I try to use the AF it never focuses correctly. It just searches in and out. Sometimes it will find focus but then goes straight back to searching for focus. I have tried it on bright sunny days as I though it may have been a bit dull for the light metring to work.

Any ideas ????

Thanks

[Ben_Edict]

Hi Guys, I have a Sigma F2.8 APO DG II 70-200mm HSM lens and it's been fantastic, but I wanted a little more reach on the lens. I got a Teleplus Pz-AF 2x MC7 off ebay. It has all the correct connections for the HSM but when I try to use the AF it never focuses correctly. It just searches in and out. Sometimes it will find focus but then goes straight back to searching for focus. I have tried it on bright sunny days as I though it may have been a bit dull for the light metring to work.

Any ideas ????

These tcs are not really intended to be SDM compatible, they just have contacts at the exact location inside the mount, as these were formerly the power zoom contacts. Thus, I guess, whether a particular tc works with a particular lens is more or less sheer luck - or not.

Ben