Suggest simple test to verify zoom level on legacy 70-210mm

new_berlin · Joined: 27 Mar 2011 Posts: 37

Perhaps this is too basic a question but could someone suggest a simple test I can run to verify if my 70-210mm zooms correctly. It's sufficient if I can verify that at 210mm, I am getting the rated close-up.

Bird and moon-shots show up smaller than I expected at 210mm. Perhaps the samples I've found on the internet are cropped, and it's my expectations that are inflated but would be nice to run a quick experiment.

Thanks.

luisalegria · Expire: 2018-01-18

Best way, probably, would be to set up a paper target with a known coverage markings for a 50mm lens (set your camera with a 50mm lens on a tripod and mark on the paper the edges of the visible image), and inside that mark calculated smaller boxes for your zooms focal lengths and see if it hits them.

On the whole though I don't think this is a very useful exercise.

You generally want a much longer FL than 210mm for satisfactory use on little birds (I'm assuming sparrow size?) and the moon, unless you can get quite close to the birds. Getting closer to the moon is a bit harder than that.

Rule of thumb - birds - 400mm+ and the more the better

new_berlin · Joined: 27 Mar 2011 Posts: 37

cooltouch · Joined: 15 Jan 2009 Posts: 9096 Location: Houston, Texas

Bearing in mind luisalegria's comments, you might still be able to get there with what you have. If your 70-210 is good optic, like the old Vivitar Series 1 70-210 f/3.5 for example, you can probably obtain decent images if you use a good 2x teleconverter with the zoom. Of course, you'll lose two stops of light. So, the lens would be a 140-420 f/6.3 or so. Getting slow, but still usable in well-lit situations.

As for the moon, that will probably be a tougher call. If you're using a DSLR with a live view function, plus the 70-210 with a 2x, then you might be able to get the moon in focus well enough to produce a suitable image. The best way to find out is to try.

ManualFocus-G · Expire: 2014-11-24

new_berlin · Joined: 27 Mar 2011 Posts: 37

PBFACTS · Joined: 24 Dec 2008 Posts: 569

cooltouch · Joined: 15 Jan 2009 Posts: 9096 Location: Houston, Texas

new_berlin · Joined: 27 Mar 2011 Posts: 37

Thanks guys for the suggestions.

With two of you recommending it, I started looking for a 7-element vivitar 2x converter...The pics show a longish teleconverter with a tube projecting out a few inches that leads me to wonder out loud whether it can really hold a lens as heavy as the Series-1 Vivitar 70-210? Assuming that it's strong enough, I am now concerned on whether the cheap Chinese m43 adapter I am using will hold up under the extra torque.

Just musing on here if someone has more thoughts, that's all.

cooltouch · Joined: 15 Jan 2009 Posts: 9096 Location: Houston, Texas

The Vivitar 2x macro teleconverter is a pretty big unit, as big as many 50mm lenses. It can definitely handle even the 1st version of the Vivitar S1 70-210, which was their biggest. As for the torque loading on your u4/3, I don't know, but I seriously doubt it would be a problem as long as everything is being held stationary. IOW, all bets are off if the rig is moving and suddenly changing directions as it's moving.

In real world usages, chances are that you will seldom move the Vivitar 2x macro's helical away from its infinity setting, which is retracted all the way in. A situation might arise where you'll run into a close-focus issue in which your lens doesn't focus quite as closely as you want, and then a bit of a turn of the 2x's helical can resolve this. Mostly, however, it is intended for use with lenses of focal lengths around 50mm for real macro extension work. Its markings for the macro helical even reflect this.

calvin83 · Joined: 12 Apr 2009 Posts: 7557 Location: Hong Kong

Don't mount anything over 1kg without any supports. Better get a tripod mount on the adaptor or lens.

luisalegria · Expire: 2018-01-18

I often use lenses over 1Kg handheld.

The trick is to realize the light DSLR (mine are Pentax) is mounted on the heavy lens, not the lens mounted on the camera ! So you bear the weight as close to the center of gravity on the lens as you can, and just balance at the camera end.

The center of gravity, btw, is often not where the tripod mount is.

Tripods are a pain in the bottom. The best part of DSLR's with image stabilization like the Pentax is that you can much more easily handhold long lenses.

visualopsins · Expire: 2025-04-11

+1 luis

With big lens cannot hold camera like President Obama! Laughing

http://forum.mflenses.com/big-smile-for-mr-president-t34436,highlight,%2Bpresident.html