On Nikon & Other Photo Gear

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To stack or not to stack Nikon Teleconverters

I never contemplated stacking teleconverters because of the loss in picture quality associated but since I just got the new TC-20EIII…why not do some quick comparison shots? The stacked combo of the TC-20EIII plus the TC-17EII gives you a 3.4x factor meaning that a 70-200 mm f2.8 becomes a 238-680 mm f9.5 on a FX body and a 357-1020 mm f9.5 on a DX Body. On a 200-400 f4 lens the stack gives you a 680-1360 mm f13 on a FX and a 1020-2040 mm f13 on a DX body. Truly impressive focals no? It will cost you a 3.5 stops light loss and AF capability at least.

Due to the optical design of the teleconverters the TC-20EIII can be used on top of the TC-17EII [but not the other way around!!] without the optical elements touching but to do this one has to remove an annoying tab in the female bayonet of the TC-17EII first. It is quite a simple procedure though, locate the 4 screws on the female bayonet of the TC-17EII [the side where your lens attaches to the tele], remove the screws and remove the bayonet with care. If you do it properly you won’t even disturb the position of the spring that is under the bayonet [note the position of the spring, just in case!]. There is only 1 correct position for the bayonet because of the lens release pin, it is really that straightforward.

Needless to say that you do it at our own risk!! It will likely void the manufacturer’s warranty and if not done properly can damage the teleconverter. If you feel uncomfortable trying this on your own go to an authorised Nikon repair center and ask them to do it for you. Many UK repair centers will remove the small tab for a small fee.

Bayonet screws on lens attachment side of the TC-17EII

Bayonet screws on lens attachment side of the TC-17EII

Locate the small tab that is almost aligned with one of the screws [see pict A below]. Take a smooth flat or half-round needle file and carefully remove material from the tab until it is almost flush with the inner part of the bayonet [see pict B]. To avoid making scratches and cuts on the bayonet surface while using the file, cover the areas next to the tab with electric insulation tape. Remove the tape when finished, place the bayonet back in the teleconverter and tighten the screws [be careful to align the threads properly! don’t force the screw in! if it offers resistance then it either the threads are not properly aligned or the spring under the bayonet is not in the right position!].

The annoying tab that needs to be removed on the lens attachment side of the TC-17EII

A - The annoying tab that needs to be removed on the lens attachment side of the TC-17EII and B - how it looks after removal if done properly

That’s it! The TC-20EIII can now the stacked on top of the TC-17EII.

Stacked TC-20EIII with TC-17EII

Quick Stacking Comparison Tests

D700, manual exposure 1/80 sec, f/11, ISO 800 with a 70-200 f2.8 VR I at 200mm with VR Off. Shots without any tele, with the 17EII, with the 20EIII and with stacked 20EIII and 17EII combo. Shots taken on a sturdy tripod with remote release and mirror-up. Blow ups of the frames taken without teleconverter, with the 17EII and 20EII were resampled in Photoshop using Bicubic interpolation to match the magnification of the stacked shot. Default Adobe Raw conversion settings [no sharpening applied], no further processing. Click on the thumbnail to download a higher resolution version.

Quick Comparison Shots

Quick Comparison Shots

Conclusions?

Although the tests were not extensive they nevertheless show the superior quality of the TC-20EIII. The blow-up of image with the TC-20EIII is actually sharper and more contrasted than the one taken with the TC-17EII alone. Between the images taken with the TC-20EIII and with the Stacked teleconverters, I actually prefer the one with the stacked teles [despite the lower contrast] but Photoshop Bicubic interpolation is not the best interpolation around. If I would resize the TC-20EIII image in ImageMagick with the right filter settings I’m sure that the differences would be minimal or non-existent and I wouldn’t need to lose an extra 1.5 stops and give up AF altogether during shooting. You to decide…

27/05/2010 Posted by | Photo Equipment Reviews, Tips | , , , , , | 6 Comments