akfishguide Loc: PA

I was just up at a Wildlife Mgt. area and there was a gentleman next to me with a Canon 7D and a 600mm F/4 lens and a 2X teleconverter on it. There are about 50,000 snow geese migrating and 20,000 swans migrating and all congregating around the lake. I asked him what he figured his magnification at and he said the 600 mm + the 2X converter would give him 1200mm equivalent and then with the crop factor it would be just over 1900mm. He was actually photographing just the heads of the swans (as they were the closest birds, and they were still quite a-ways away) but he also showed me a photo he had taken of a Great Blue Heron that I really could not even see on the far side of the lake. It got me to thinking about my own equipment. So here is the question. If I had used my Nikon D7000 (1.5 crop factor) and add a 2X and a 1.4X converter with my 70-200 f/2.8 lens, what would be the equivalent focal length in mm? (hope that is the right terminology) If I do the math one way and multiply the 200 mm by the 2X it would equal 400mm equivalent. The the next would be the 1.4X which would take the 400mm to a 560mm equivalent, and then add the crop factor of 1.5 that would give me an 840 mm equivalent lens. But if I add the 2X + 1.4X + 1.5 crop factor together and get a 4.9X equivalent magnification, which when multiplied with the 200mm and gives me a 980mm equivalent factor. Which would be right? What would the proper shutter speed if I used a 1/focal length as the lowest shutter speed. Now I did use the set-up and just used a 64 ISO on a bright sunny day and took some photos using the spot metering withing the camera to take photos. I also varied the photos by using several stops using up to a -1 EV just to get a range of pictures, (the birds are bright white and they were actually too far to get anything more for me than group shots using this setup) plus I used my D810 full frame camera and not my D7000, but was just wondering if someone could guide me with the question. Should I calculate an 840mm or 960mm or are my calculations totally wrong? Just a thought for future reference.

TriX Loc: Raleigh, NC

You multiply the various factors, not add. (840 mm effective FL)

Longshadow Loc: Audubon, PA, United States

The teleconverters multiply what is in front of it. It's cumulative. You can't add the multipliers together then multiply by the lens size.

CaptainC Loc: Colorado, south of Denver

If you are using Nikon TCs, I am pretty sure you cannot stack them.

CHG_CANON Loc: the Windy City

You're missing the fact that you'd lose autofocus in this configuration and manual focus would border on impossible in less than full sunlight. The stacked extenders lessen the light reaching both the sensors and the mirror used to focus. I'm going to assume the person handing you their camera was using a 7DII as the older 7D would not autofocus the f/8 effective aperture of the 2x extender with the 600mm f/4 lens.

You would need to check the manual on your candidate Nikon bodies as well as the extenders and the lenses. Not every extender can be mounted to every lens. Nor can all but the top-line camera bodies retain autofocus for effective apertures at f/8. No camera brand currently retains operational autofocus at apertures less than f/8.

akfishguide Loc: PA

Thanks everyone. It was just a crazy thought that went through my brain (shows you how much room there is there) :-)

JeffDavidson Loc: Originally Detroit Now Los Angeles

You cannot effectively stack the two tele extenders in addition to which speed of your lens would drop significantly the 2x extender would make the 70 to 200 F 2.8 a56 and then it would become an f8 with the additional extender you would lose autofocus it's a bad idea

SharpShooter Loc: NorCal

I'm just gonna say that if you start talking to guys that shoot with 600mm lenses...., you really should not start to do ANY thinking!!!
That's really dangerous unless you can no longer get your wallet into your pocket!!!
SS

Bill_de Loc: US

There is a tab that needs to be filed down in order to stack Nikon tele converters. I know a guy that used to do it with a Nikon 400 2.8 and got very acceptable results. He doesn't need to do it anymore as he is now a Canon Explorer of Light.

--

Howard5252 Loc: New York / Florida (now)

Here's the right answer. You take your setup > walk outside of your house > take some picture of distant objects > look at your results. That's it. Skip the math.

jerryc41 Loc: Catskill Mts of NY

Use one or the other, but not both at the same time. The greater the magnification, the greater the potential loss in quality. Still with a Nikon 70-200mm and a Nikon 1/.4TC, you should be fine.

NikonCharlie Loc: Kansas USA

As TriX said, 840mm is the answer. F8. It can be done, on the TC14 remove the extra mount tab and the 2X will snap onto the 14. I have a photo of mine somewhere to show this. I'll try to find it.
(occasionally) I use 14x or 17x on my 500 f4, but not the 20x. 20x works well with the 300 2.8.

bdk Loc: Sanibel Fl.

doing math gives me a headache, so I didn't even try to figure it out , I do think it would be cheaper to just buy a 600 MM lens....

NikonCharlie Loc: Kansas USA

What 600mm lens is that, cheaper

jerryc41 Loc: Catskill Mts of NY

Yes, that would definitely be cheaper than thinking.