Moose,
Yes, I have that 'L' and focusing was working just fine in that range for
long distances until last weekend where as maybe I was shooting further
away, but I don't think so.
Yes, none of my shots over much of a distance in the last week, have been in
focus yet the week before I had no focusing troubles.I was able to turn the
lens until it hit the end of it's movement and it just didn't quite make it
into focus, even in the viewfinder.
Come to think of it, the air was colder than it was the week before. Last
weekend the troubles I was having was in the morning, but about 2-3 PM it
was OK, when it was a good 20 degrees warmer, I was shooting seals, sea
Lions and otters at Point Lobos.
Where I was shooting yesterday was 2 miles from the coast just as the dairy
lands end and the woods start, so the moon was coming up over your house.
It's your air that gave me a bad time? (smile)
Yes, I have that tab, it hasn't been in the lens as it wasn't there when I
got it, this has a ND4X lens in it that makes everything a lot darker. I
will try to check this out today to see if that brings the moon into focus
as it comes above the horizon about 3 PM today.
Is there a better filter that I could use that isn't so dark and light
robbing?
Yes the good vivitar teleconverter was just magnifying it. I'll let you know
what happens when I try this today, with and without the ND4X filter and or
the teleconverter.
Thanks a lot for the suggestions and the weather data.
Scott
----- Original Message -----
From: "Moose" <olymoose@xxxxxxxxx>
To: <olympus@xxxxxxxxxx>
Sent: Wednesday, March 28, 2007 2:12 AM
Subject: [OM] Re: focusing question
> Scott Peden wrote:
>> A bit over a week ago I lucked into a Sigma 600/8.
>>
>> I noted immediately that at 200 or so feet, infinity was to far of a
>> focus, I had to back off a bit.
>>
>> Last weekend It was just barely focusing all the way over to infinity.
>>
> Two things here.
>
> 1. Many long lenses have a sort of an "infinity zone" because they will
> focus slightly differently at different temperatures. Look at your lens.
> If you turn it all the way to the stop, the red line is lined up with
> the infinity symbol. To the right of that symbol, you will see a
> horizontal line ending in a vertical line. The red line and the vertical
> white line define the area in which you may find infinity focus.
>
> You may have the idea that simply running the lens against the end stop
> is infinity, but that isn't true of many long and/or zoom lenses and
> that sideways, inverted "L" is the standard marking. You have to focus
> with the viewfinder even for infinity.
>
> 2. 200 feet isn't infinity for a 600 mm lens I don't know the exact
> numbers, but for a lens that long, 200 feet should focus closer than
> infinity. You need more like half a mile to be certain of infinity.
>> 2 days ago shooting Red-tailed hawks, I noted that it didn't seem to want
>> to go far enough to focus.
>>
>> Tonight when trying to shoot the moon, all the way over just didn't seem
>> in focus
> In both cases, do you know for sure if it would focus, or just not sure?
> On nights with atmospheric disturbance, exact focus may be hard to
> determine. Did the shots end up out of focus?
>
> Looking from the rear of the lens, 90 degrees CCW from the red focus
> line, there is a break in the back end of the lens. Is there a plastic
> tab in that hole? If so, pull it out and check if there is a small
> filter mounted on it. The filter is part of the optical formula and a
> neutral one should be in there when not using any other. It's possible
> that without it and in cold weather, infinity focus can't quite be
> achieved, although whether it would be in hot or cold weather I don't
> know for sure.
>
> I can assure you that a properly operating 600/8 with filter will focus
> nicely on the moon; I've done it. Getting a sharp image is another
> matter around here, as there is a lot of atmosphere wiggling around
> between me and the moon.
>> and with the Vivitar 2X Macro telefocusing teleconverter, there was no
>> way to turn the dial far enough to get the moon into focus, just a bit
>> shy.
>>
> - If there is a problem getting quite to infinity anyway, the 2x may
> just be magnifying it.
>
> - Or that teleconverter, which is primarily designed for much shorter
> focal lengths, just doesn't get along with a long mirror lens.
>> Am I loosing it, or is infinity closer than the moon and somewhere under
>> 300 feet?
>>
> I guess you already know the answer to that.
>
> Moose
>
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