Adding a supplementary lens to a zoom

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MikeBinOKlahoma
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Adding a supplementary lens to a zoom

Post by MikeBinOKlahoma »

While shooting landscapes, I sometimes carry just a wide-angle zoom and a short telephoto zoom, going without any macro capability. I often add a 50mm macro to that mix, but that lens is still awfully short for photographing anything with a pulse. I'm considering trying to use a supplementary lens on the telephoto zoom (Canon 70-200/4) to get some additional macro capability.

My impression is that the Canon D-series diopters and the Nikon diopters are the only ones that are likely to give me image quality I'm satisfied with. Unfortunately, nobody makes one to fit directly on the 70-200/4's screwball thread diameter (67mm). The Nikon 6T does have a 62mm version. I'm considering using a 6T with an adapter to mount the 62mm version on my 67mm lens. I'm speculating that since I'd usually be shooting stopped-down for a closeup shot, vignetting shouldn't be too bad, even on a full-frame camera.

I've run through the formulae Tom generously supplied us, and it appears the 6T would give a focusing distance of a bit over a foot, and a focal length of about 125mm on the 70-200. I've realized I don't know the formula for focal length, distance, and magnification, but comparing the combination to other lenses where I do know the magnification, I'm guessing I'd get about .7x or .8x. With the larger focusing distance, this is a considerable improvement over my 50mm macro, IF it works as I think it will.

I have several questions I hope to get advice on:

1) Am I overlooking any high-quality supplementary lenses that would be a better fit at 67mm?

2) Am I correct in my belief that I'd get about 3/4 life size at a bit over a foot away? (Tom, your help is sought! :) )

3) Does anyone have any advice on using a 62mm filter thread on a 67mm lens? Am I naive to think I can pull this off, even stopped down?

4) Is there anything else I'm overlooking here?
Mike Broderick
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"I must obey the inscrutable exhortations of my soul.....My mandate includes weird bugs."--Calvin

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twebster
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Post by twebster »

Hi ya' Mike :D

I'll take your points in order...

1) The Nikon 6T is the closest to your lens size without you having to buy a new lens hood. :D Canon makes the 500D (+2 diopter) in 72mm thread but you would have to buy a 72mm lens hood. You should never use a supplementary lens without a lens hood. The 500D in 72mm is pretty pricey, too. US$119.95 at B&H Photo :!:

2) If you purchase the Nikon 6T, this supplementary lens has a diopter power of +2.9 and a focal length of 334mm. You can calculate image magnification of the lens set at infinity focus by dividing the focal length of the lens by the focal length of the supplementary lens. If you use the Nikon 6t then you would calculate 200mm/344mm = 0.58. The image magnification will be 58% of life size or 1:1.7 image magnification.

The Canon 500D has a diopter power of +2 and a focal length of 500mm. Using the previous formula, 200mm/500mm = .25. Image magnification with the 500D supplementary lens would be 25% of life size or 1:4 image magnification.

Of course, these are calculated for the 200mm focal length of your zoom lens and with the zoom lens set to infinity focus. Image magnifications will increase as you focus the lens closer. I just can't calculate how much more they will increase.

3) If you purchase the Canon 500D you won't need to worry about vignetting but you would be giving up a lot of magnification (and giving up a lot of dollars :!: :shock: ).

I would purchase the Nikon 6T, myself, and only use the 200mm setting on the lens. The shorter the focal length of the lens the more likely you will get vignetting. If you get any vignetting at the 200mm setting it will be with the lens focused at infinity focus. As you focus closer, the image circle at the film plane gets bigger and pushes the vignetting out of the image area.

Stopping down the lens will only make any vignetting from a smaller filter sharper. Vignetting from using a smaller size filter is not the same as vignetting from inadequate coverage of the lens. Vignetting from using a smaller filter is caused by the lens imaging the smaller filter ring itself. I don't think you have to worry about vignetting too much as long as you use the longer focal lengths and focus closer than infinity focus.

4) I hope this helps you out, MIke. I don't see anything else that you are overlooking. :D

Best regards as always, :D
Tom Webster
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gunn
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Post by gunn »

hi mike

this is a rather naive statement/question. i was curious after reading (rather very intently) Tom's excellent articles. can you use a canon TC, either the 1.4X or the 2X with the 70-200f4L ? if possible, it would increase your XXX whilst maintaining your working distance?

regards
benGUNN

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MikeBinOKlahoma
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Post by MikeBinOKlahoma »

gunn wrote: can you use a canon TC, either the 1.4X or the 2X with the 70-200f4L ? if possible, it would increase your XXX whilst maintaining your working distance?
Yes, you can use teleconverters with the 70-200 f/4. With your 20D, you could use a 1.4x tc and maintain autofocus. A 2x tc would work on your 20D, but you would lose autofocus. I find the image quality quite good with a 1.4 tc. With a 2x tc, it is useable, but not the greatest.

Either TC will increase your magnification, so you'll get a bigger image of your subject at the same working distance. Or you could be a bit further away and get the same size image.

In my experience, good quality TCs work well with good-quality prime lenses. With zooms, TCs don't seem to work as well, though with really good zooms (such as any of the three Canon versions of the 70-200 zoom), the 1.4 TC is still decent.
Mike Broderick
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"I must obey the inscrutable exhortations of my soul.....My mandate includes weird bugs."--Calvin

(reposts on this site of my images for critique or instruction are welcome)

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MikeBinOKlahoma
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Post by MikeBinOKlahoma »

As an aside, if you're pondering getting the 70-200/4, I do think highly of the lens. It's my favorite lens for shooting landscapes, and image quality is very good. Also much lighter and less expensive than the f/2.8 versions.
Mike Broderick
_____________________________________________________________
"I must obey the inscrutable exhortations of my soul.....My mandate includes weird bugs."--Calvin

(reposts on this site of my images for critique or instruction are welcome)

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