bob_atkins

I've looked at 2 different Fuji 645 folders and both had the same

problem. When the temperature gets really cold (freezing or below)

the shutter release sticks. That is the small red "T" button

does not go all the way down when the main shutter release is

pressed, so the shutter does not fire. If you gently push the "T"

button all the way in (doesn't take much effort), the shutter

then releases normally (i.e. the exposure is correct).

<p>

Anyone else seen this? Since I've seen it on two examples, I

assume it's a generic condition (the odds of 2 cameras having

the same identical fault seems small otherwise). Anyone know of

a good repair shop with experience in working on the 645 folder?

Does anyone know the area around Sandy Stream Pond in Baxter State

Park (Maine). Is it a productive spot for Moose watching in the fall?

Are there other good and reliable "moosey" areas nearby? Does anyone have current predictions of peak fall foliage timing in the area?

I wouldn't worry over small differences in manufacturer's data sheets.

The conditions under which their numbers are obtained are so unlike

those of the real world that small differences do not readily

translate into predictions of real world imaging quality.

<p>

The only way to tell if there is any sensible difference between Sensia/Sensia II/Provia/Astia is to shoot it in the

field and look at the slides. You won't get that information

from the spec sheets. If you compare data from different film

manufacturers you will be in even more trouble! If I remember

right, according to

the spec sheets, Kodachrome 25 doesn't resolve any more lp/mm

than Sensia 400.

The simple answer is that any lens will image a star as an aberration

limited spot. In a perfect lens, this is a diffraction limited spot.

Now the size of the spot does depend on relative aperture in the

diffraction limted case, so you could argue that a faster lens

will give a brighter spot (if the two lenses have the same

physical aperture). However most lenses aren't diffraction limited,

especially at fast apertures, plus the light spread due to the film

will significantly increase the size of the spot on film, so for

practical purposes, it's the physical aperture of the lens which

determins the brightness of the stars on film.

<p>

Russ: If everything was <b>perfect</b> we would still get images!! While

the star may be as close to a perfect point source as we are likely

to get, the image of it isn't. It

will always have a real physical size due to diffraction. Your

arguement fails in a number of ways, including the 2nd law of

thermodynamics (I think!). Where would the photons go in your

"perfect" system!!

<p>

Small differences in brightness and image size (brighter stars

form larger circles on film due to light spreading effects) can

be due to very small differences in focus accuracy. It's very

hard to get perfect focus on stars. Astrophotographers go to

great lengths to do this, they don't just focus on the screen.

Tricks like looking at the extiction of the image using a knife

edge are used to get "perfect" focus.

Do you think they actually use mechanical gyros to sense motion?

I know Canon talk about "gyrosensors", but I'd assumed they

probably meant some sort of accelerometer sensor, not a spinning

top. None of the literature I have describes the motion sensors

in any detail nor is an operating temperature range is specified for

the lens.

<p>

The Canon IS binocular specs talk about the "Vibration Detection

System" containing "two vibration gyro sensors". They also talk

about it's "almost instant on" functionality, which again makes

me suspect they are using some sort of "solid state" device, not

mechanical gyros.

I didn't include a scale on purpose because if I did, people would

leap to all sorts of unjustified conclusions (especially if they

tried to compare several different plots given in the original

article for different camera bodies).

<p>

The vertical scale is proportional to angular deflection in the

vertical plane (i.e. how much the lens "wobbles" up and down).

In a crude sense, the magnitude is proportional to the induced

vertical blur of the image.

<p>

The plot shows a general idea of what happens during a typical

SLR firing cycle. It's illustrative of the points to consider

wrt MLU.

To determine image degradation, shoot test targets with and

without MLU, don't try and back that info out of vibrational

analysis plots! It's easier, much more reliable, and takes

into account <b>all</b> the variables involved.

Like I said, it's a least common denominator approach. If you left

the mirror locked up for a long time with the camera pointed at

a bright light, I'm sure you'd get leakage though a single shutter.

It might need 10 hours pointed at the sun, but you could do it

if you tried. Some shutters might only need 10 minutes pointed

at a bright source - who knows? Nikon just play it safe. They

don't want complaints (and they want to sell you the expensive

bodies).

<p>

If they put true MLU on some single shutter bodies, eventually

some idiot would complain about light leakage under conditions

like those suggested above. So none of us get MLU. With Canon

we get a 2 second delay. Not enough to let light through the

shutter, long enough for mirror induced virations to die out.

No chance of an idiot getting it wrong by leaving the mirror

up all day!

<p>

Note that most (all) AF cameras have mirrors which let some light

through anyway (to get to the AF sensor). While most of the light

is defelcted from the shutter via a secondary mirror, some must

get by. It's all a matter of degree (and "clever" marketing!).

Minimum shutter speed for a 600mm lens? Hard to say. Certainly

speeds between 1/30 and 1/8 would be the bad ones, maybe extending

out to 1/4 or 1/2. On a less than ideal tripod, even 1/60 could

be bad. I've seen images shot at 1/125 with an 840mm lens get

better when MLU was used.

<p>

With a long lens (400+mm), I'd certainly use MLU at anything

slower than about 1/60, assuming a static target and no need

for "decisive moment" shots.

"Leaky" shutters are often cited as an excuse for not providing

MLU. Canon get around it by providing "pre-fire", i.e. the mirror

flips up and the shutter fires after a short delay (1 or 2 seconds).

Nikon claim that MLU is a pro-only function, and only the F4 and

F5 are "pro" bodies (Note: Please no discussion on what a "pro"

body is!!! We all know it's a meaningless term).

<p>

Single shutters, if left long enough unprotected by the mirror,

would (in principle) allow some light leakage. In practice, it

wouldn't be a problem for photographers with a brain, but you

have to design for the lowest common denominator I guess.

<p>

There's still no excuse for not providing some sort of pre-fire

function, except the usual "most people don't need it". In modern

AF cameras, it's just a software change and another button!

No matter how "vibration free" you think your camera is, it isn't!

Some cameras are better then others of course, but leaving MLU

(or pre fire) off a camera is nothing but a marketing trick. Most

people don't miss it, but for anyone using long lenses it's

an essential function to have available. You might only use it

5 or 10% of the time, but when you need it you <em><b>need</b></em>

it!

<p>

Not owning an EOS-1n, I don't actually have true MLU. I have to survive with mirror pre-fire and a 2s delay (makes catching that

"decisive moment" ticky!). If I need to catch a moment, I'll use

an EOS RT, which has no moving mirror and you don't need Don's

binocular trick!

Depth of field for macro work depends <b>ONLY</b> on the magnification

and the f-stop in use. It is independant of focal length. If you

take 1:1 shots with a 50mm macro or a 200mm macro (at the same

f-stop), you get exactly the same depth of field.

<p>

If you want to get

pedantic, there <em>might</em> be a very small difference in DOF, of the

order of less than 1% or a few microns. I'd have to run the exact

numerical solution to the DOF equations to be sure, but the

difference (if it exists) would be so small as to be meaningless

for any practical purpose.

I believe that this <em>is</em> the rainy season (or at least the

thunderstorm/flashflood season) in that area. I carry a radio

which receives the NWS broadcast info (164 MHz or thereabouts)

when I go on trips. However you would need to know the area

well to know that a thunderstorm that didn't drop any rain on

the canyon itself could result in such a disaster. I believe

there was a NWS (National Weather Service) warning in effect for the

area at the time of the incident.

You have to answer the question asked. If someone asks about

a 135-400 Sigma zoom, it's not likely they want to fork out

$4000-$8000 for a prime 400/2.8. You could answer any question

about telephotos by saying "get a 400/2.8"! It's like recommending

everyone who asks you about which car to buy get a Ferrari!

<p>

The Sigma lens is perfectly fine for many photographers. I've seen

much worse lenses highly praised! I wouldn't want to depend on one

myself, but a lot of photographers are happy with them. It's a

middle of the road lens with price and peformance to match.

<p>

Many amateurs wouldn't want the weight and worry of carrying

a 400/2.8 around, even if they could afford one. The biggest,

fastest lens isn't the best lens for everyone.

Just as an historical note, when the original Elite came out 2 or 3

years ago I tried some. It seemed OK, so I bought a batch to take

on a trip. It was horribly yellow. It more or less

ruined quite a number of shots I took on that trip to Yellowstone.

Fortunately I also shot Kodachrome and Fujichrome on the same

trip, so it didn't ruin all my work. That experience turned me off Ektachrome, possibly forever.

Lots of people like and trust the various varieties of Elite

film. I am not one of them.

What's supposed to be so special about them that you would

consider one rather than a Hoya, Tiffen, B+W or Heliopan?

<p>

I wouldn't buy anything on the basis of a mention in OP, and

especially not if that mention came from someone associated

with the company involved.

<p>

And yes, this question probably belongs in the original Q&A forum

since it isn't really nature specific. The only real connection

with nature photography is the mention of OP!

Has anyone used a "Scopepack" to carry a long telephoto in the

field? For those who don't know what it is, it seems to be a

basic "backpack", where the pack is a padded tube (24" x 8" I think), with a few small pockets on the side. Just wondering how effective

it is (how well built, whether the harness is up to the job etc.).

<p>

The advantage over a conventional photo backpack is that it's

cheap (under $100), the disadvantage I assume, is that you can't

carry much more than a big telephoto plus a few supplies.

I've tried the Tamron 1.4x with the 75-300IS too. My opinion is

that AF is too unpredictable to depend on. Sometimes it will lock

onto a subject, usually it will hunt and give up. This makes

"grab shots" something of a hit and miss affair. It does depend on

conditions, the lower the light and the lower the contrast the

less likely AF is to work of course. You do get the "green dot"

and "beep" focus indication in manual focus though, which can be

useful.

<p>

Image quality is also adversely affected, as you would expect.

Since (in my opinion) the image quality at 300mm is not great to start with

(but it's not aweful either!), adding a TC is prety much an

"emergency" measure, not something to plan on doing on a regular

basis if you need high (technical) quality images.

Well, the nature forum is linked from the top of the Q&A page

and it's linked to in several places from the "Ask a question"

page, so you can't blame me if you didn't see it!!

<p>

Equipment reviews really belong in the original photo.net section

(where Philip decides what's appropriate). More appropriate

for here would be technique articles or nature travel articles.

There's more to this forum than just the Q&A page! In order to

cut down on repeat questions - and to make the forum pages more

useful, please think about writing a short article on some

popular topic. A few paragraphs may be enough in many cases.

Take a look at the <a href="http://www.photo.net/photo/nature/">

Nature Forum Home Page</a> and see if there is something you

would like to contribute. Thanks

<p>

Here endeth the solicitation!

You have only 3 choices:

<ul>

<li>Stay <em>in</em> the park if anywhere is still open (call and find out)

<li>Gardiner at the North entrance

<li>West Yellowstone at the West entrance

</ul>

There are no other town close to the park. Write or call the

chamber of commerce in each town for an accomodation list (I

know W. Yellowstone has one, I presume Gardiner does too).

TC work better for macro work because you are normally stopped

down, thus reducing aberrations. At f22 most lenses are pretty

much the same as far as sharpness in the center (though they may

differ in field curvature and off-axis aberrations).

<p>

TCs are fine for many people (say the general Pop Photog

audience). I've seen excellent results with a 1.4x TC on many

lenses. I've yet to see any lens that gives what I would call

excellent results with a 2x TC. Maybe the Canon EF300/2.8L + 2x

comes closest, and even with that, stopping down a stop makes

a significant improvement (600mm at f8).

Has anyone here actually tested the 70-200/2.8L + 1.4x and 2x TCs

themselves, and compared it with the 300/4L (and 1.4x) and the

400/5.6L?

<p>

I've read Lepp's comments (which are a bit mixed and not all

that clear - he earlier rated the old 80-200/2.8L with the

Tamron 2x TC higher than the current 70-200/2.8L with the Canon

2x TC!) and I've read a few "user comments" from people

who's photographic standards I don't know (what's great to

one person may be just OK to someone else!). I've also read the

usual advertising hype.

<p>

I have tested the 80-200/2.8L with the Tamron 1.4x and 2x TCs and

the quality just isn't there compared to the 300/4L and 300/4L

plus 1.4x. It's OK, some would say good, Lepp said a "7"

rating on his scale (decent) (but the 70-200/2.8L + Canon 2x TC

only got a "6"!).

<p>

Actual user input from experienced users in this forum would

be valuable information. I don't belive that the 70-200/2.8L

with a Canon 2x TC would come close to the 300/4L + 1.4x TC or

the 400/5.6L (which <em>current</em> testing indicates is good).

I'm willing to be shown to be wrong however!

Since you already have a 28mm lens, the jump to a 24 just isn't

that big, hence a 20mm might make more sense. The advantages of

the 24 are that it takes the same 58mm filters as your 28-105 and

it's cheaper than the 20. If you had a 35-whatever zoom, the

24mm would probably be the more useful lens.

<p>

The 20-35 (non-L) zoom is pretty good. It shows more flare than

the 24, but is comparable in sharpness stopped down. Shooting

directly into the sun you can see the difference in flare, but

on "normal" shots you don't see it. The disadvantage of the zoom

is it takes 77mm filters and is larger and heavier than 24mm (but

it's actually lighter than the 20mm) - and of course it duplicates part of the range of your 28-105.

<p>

I've owned and shot all three lenses. There really isn't anything

wrong with the 20-35USM. The 24/2.8 is better if you intend to

shoot at large apertures, but for landscape work that's just not

an issue. It's only real advantage is somewhat less flare (and

better "sun stars") when shot into the sun, stopped down, and the

fact that it takes 58mm filters.

Unless you are <b>really</b> serious, renting a 600/4 could be

a disaster! You have to look after the thing like a child - it

goes everywhere with you. It's big and heavy and you need a big

and heavy tripod and head to go with it. It's no good "back in

the car", so you have to carry it around with you - which means

hauling and extra 20lbs around. There's also something of a

learning curve to using it effectively.

<p>

It's a great lens, but it's not something to be taken lightly

(no pun intended)! Many photographers would be happier with

a 400/5.6, despite its limitations.