Warbird Information Exchange

Hey guys do those teleconverter lenses work good at all? I have a Nikon D40 DSLR with the regular lense, and then I have a 70 300 mm zoom lense as well. I was wondering if I should look into these as well. Also what do the filters do?

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Chris Henry
EAA Aviation Museum Director

For me, Teleconverters don't seem to work very well.

I've got Canon eqpt and a 1.4x and a 2.0x. I don't use either more than once a year or so. Mine take away the autofocus on the lens. YOuhave to focus manually, fine for subjects that are not moving. Also they cut the F Stop in half and make pictures darker (which can be corrected), but still not as good.

Filters, I have some, keep a 1A on each lens to protect it against damage. If I need a "filter" I apply it in Photoshop.

I shoot a Canon 5D 12.8MegaPixel, with an extra battery pack. I carry about 12 8Gig CF cards from 120X to 266x. Lens all Canon L series (which means $1200 to $200 each) most shooting with a 24-105 F4.0 IS; FlyBys with 100-400 F4.0 -5.6 IS; Close inside 70-200 F2.8 IS; Wide is a 16-35 F2.8. Also use a Canon 580FX flash when I need it. For Flyby shooting I use a Manfretto Carbon Fiber MonoPod with the 100-400. Which means I can usually get full frame shots with crisp details (canopy pilot names; duetz (spelling) fasteners, etc). Works very good.

Mark H

Thanks for the info. I am going try some of that out.

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Chris Henry
EAA Aviation Museum Director

I am looking for filters now, and saw uv filters. Would this be the one that I want?

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Chris Henry
EAA Aviation Museum Director

Chris

I always have a UV or skylight filter on my lenses, if nothing else but to protect them from scratches, a scratched filter is a lot cheaper to replace than the lens!. The added benefit of haze reduction is a bonus

Dave

Cool, I am going to get one after work. This is going to sound dumb, but do they just screw on on the end of the lense?

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Chris Henry
EAA Aviation Museum Director

Yes they do screw on, but you have to make sure you get the right size for your lense. Usually on the lens somewhere is a number in MM's indicating the diameter of the lense and therefore which filter you will need.

Regarding the teleconverter question- I have alway found that they are okay for still shots and when usuing a trypod, but the negative impact on the F stop of the lense and its ability to focus make them counterproductive. Usually when I have one on my camera they magnify every lake shake or movement of my hand so things aren't as sharp.

Thanks very much for all of the great info here. I have seen some of the great pics that you guys post, so that really made me want to get some good shots this year with my new camera.

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Chris Henry
EAA Aviation Museum Director

The loss of light with a teleconverter is why the autofocus function doesn't work well. Lenses typically autofocus with the lens at maximum aperture, then stop down for the exposure. Most lenses have difficulty with autofocus when the maximum aperture gets smaller than f5.6. If you have an f4 lens, then with a 1.4X teleconverter, you have an equivalent maximum aperture of f5.6, which puts you right at the edge of autofocus operation. With a 2X teleconverter, your effective aperture is f8, which is beyond the limits of most autofocus lenses.

Another filter you want to consider is a good circular polarizer. The polarizer can darken the sky and make clouds pop out, and also reduces glare from metal and Plexiglas surfaces. It also makes colors more vivid. If you use a wide-angle lens frequently, get a polarizer one size larger than the normal filter size for the lens, and also get a step-up ring with the lens diameter at the small end and the filter diameter at the large end. Quite often when you use a filter on a wide-angle lens, the corners of the photo will be cut off by the filter. If your camera doesn't have 100% viewfinder coverage, you may not be able to see this effect in your viewfinder.

Walt

Another question from a new guy here. I have heard you guys talk about cleaning the sensor. What is that on the camera, and what should I clean it with.

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Chris Henry
EAA Aviation Museum Director

Better sit yourself down and read through this website: http://www.cleaningdigitalcameras.com/

All you need is in there, but make sure you read through all of it. 20 minutes of your time is probably still cheaper than buying a new camera.

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A Little VC10derness - A Tribute to the Vickers VC10 - www.VC10.net

The sensor is the "film replacement". That is what the image gets exposed to when you push the shutter. Like everything else in the camera, it can get dust or dirt on it. There are a variety of cleaning kits available commercially for cleaning the sensor, but do so carefully.

I don't use teleconverters at all. I had one years ago when I shot with Film and found the focus was not as sharp, and everyone else has already covered the F-stop issues.

I will tell you why I always have a UV filter on my lenses. I bought a new Nikon D50 last year in February and also picked up a 70-300 lens. Sometime during the middle of the season, something got picked up and tossed at the lens. I noticed a small black spot on all my pictures. I pulled out the lens wipes and started cleaning. One spot just would not come off. Closer inspection with a magnifier revealed my worst fear, a very small chip in the lens that is less than a year old (at that time). A chipped UV filter would have been way less expensive to replace.

So when I got my new lens (Sigma 50-500mm), I ordered the UV filter with it and put it on right away.

Also, in my experience, the quality of the filter will matter. B+W makes an excellent albeit more expensive filter. Hoya tends to make a decent value filter as well. I have seen some bad results from Tiffen filters and some lenses. Lens converters can workout alright on fixed lens cameras but if you have an SLR or DSLR seems like a better idea to go with just a longer lens.

I use teleconverters all the time, and don't have a problem, but there's a few factors involved.

The aperture/light loss has been covered, but I'd like to add a bit to that, if I may.

An autofocus system can't function below f8. If you can set your camera in 1/3-stop increments, then you're good up to f7.1, but above that and you're in trouble.

Remember that most zoom lenses in the consumer lines have variable minimum aperture, such as a 70-300 zoom that will open up to f4 in the 70mm range, but f5.6 by the time you zoom all the way out.

There are two primary factors in the sharpness of an image using a teleconverter...

1) Quality of the glass in the teleconverter. Your image is only as strong as your weakest piece of glass, so a $7500 fixed telephoto lens is rendered ineffective by a $50 teleconverter. I haven't been in retail for awhile, but I'd look to Tamron's better series, for example. (There's also a factor called chromatic abberation involved here, but I won't go into it unless y'all want me to.)

2) Camera shake. Remember that you're tracking an aircraft moving at probably 200mph+ and trying to stay with it while having a shutter speed slow enough not to freeze the props. Adding a teleconverter magnifies any movement you mage (think of the shake you see in a zoomed-in handheld video image).

One other suggestion for the digital folks...set your camera to the lowest ISO you can, which will give you the highest quality image, then crop as needed.

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"Anyway, the throat feels a bit rough...the legs have gone...but I'm still able to chant, so let's get going."

Joe Strummer, 1999

So I think I might have the wrong size on the big lense. I have a Quantaray 70-300mm lense, and I bought a 67mm fliter. is that wrong. The filter for my smaller lense went on great. The one for the bigger one, fits, but doesn't really fasten on to it.

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Chris Henry
EAA Aviation Museum Director