greg_erker

By the way, Boz's site has the optical diagrams for pretty

much every lens Pentax made/makes (<a href="http://www.bdimitrov.de/kmp/">click here</a>).

<p>

Greg

SMC stands for Super Multi Coated. They put a 7 layer coating

on every air-glass surface. Don't know about the glass-glass

ones.

The SMC 135mm f2.5 lens is very well regarded. The Takumar one

(non-SMC) isn't. It isn't even f2.5 as far as I can tell since

135/2.5 = 54mm and that lens has a 52mm filter thread.

Greg

Oops: replace "fine" with "find".

If the shutter is out of tune the flash may not sync at all

speeds. You can easily check it by shooting the camera with

the back (and aperture) wide open. Aim the flash at a wall and

when you trip the shutter you should see a circle, not a circle

with the shutter blades partially visible, or worse no flash at

all.

Greg

The link to the diacord manual is <a href="http://www.angelfire.com/ca/erker/diagmanual.html">here</a>.

<p>

I'm not sure why you can't access my web page.

<p>

In any case it does have a hot shoe but the shoe is made so the

flash slides in from the front (not the back like modern cameras).

So unless your flash head can turn around 180 degrees you won't

be flashing your subject. Also the lighting will be really ugly

since the light will be coming from the side, not above. You can sometimes fine L-shaped brackets that have a grip on the vertical

part of the L and a shoe on the top of the L. Then the light would

come more from above. You would need to connect the flash with a

PC cord in that case, unless the bracket had a hot shoe and PC

cord built in.

<p>

The Diacords have leaf shutters so it will flash sync at all speeds

(just make sure the shutter is set to X for electronic flash).

<p>

Shutter speeds are 1 sec to 1/400th plus B, later models have 1/500th

as the top speed.

<p>

Cheers - Greg

I used a hacksaw on my 700DX centre post. Worked fine.

Then I drilled two holes the the bottom cap use to hold

itself in.

Don't use wax if the LCD has an anti-reflection coating. It

will negate the AR coating I would guess.

Don't forget the Pentax fisheye zoom (17-28 mm).

At the widest it is 180 degrees on the diagonal. At 28 it

still has some barrel distortion and shows a wider view than

a 28mm rectilinear lens (90 degrees diag vs 75 for the rect 28).

<p>

<a href="http://www.pentaxusa.com/products/lenses/lensemodel.cfm?lensetype=35mm&lensemodel=F%2DZOOM">Link to fisheye zoom</a>.

<p>

I've taken apart a number of Diacords and Ricohmatic 225's.

You will have to remove the front

panel to remove the front elements as far as I recall.

To do that you need to peel off the front leatherette and then

remove about 6 tiny screws to remove the panel. Then you should

be able to unscrew the front group from the shutter.

Good luck - Greg

You should read the reviews of the medium format digital backs

on www.luminous-landscape.com if only to see that full frame

(35mm) isn't the ultimate, but also to see the tradeoffs in

going to bigger sensors, bigger MPs etc.

Greg

You may get more help on the 14n problems from the people on

dpreview Kodak SLR forum.

Greg

Multiplication factors don't work with fisheye lenses and

that's what I'm guessing an 8mm lens is.

The best way to see the effect is to take a 35mm photo done with

the lens and do the 1.7x crop from the middle of the shot.

Greg

<a href="http://www.eframecentral.com/products.html">eframecentral.com</a> seems to carry a wide selection of digital frames, including the Wallflower ones.

<p>

Greg

The Pentax 555 is pretty small though I don't know if it is the

smallest. The Pentax Optio S4 is really small though "only"

4MP. The problem with going for small is that the lenses may not

be up to the task of giving you the resolution that the sensor

has.

Greg

Douglas,

I'm not sure how your ZX-7 works but here's how my PZ-1p

behaves. Mount a 50mm lens. Set the aperture wide open. Aim

the camera at an evenly lit white wall. Note the shutter speed

the camera picks.

Unlock the lens and turn it CCW as though you were going to

remove it (careful not to change the aperture). Don't pull it out of

the camera yet. Notice that the shutter speed is now much lower.

This is because the camera thinks the lens is set to f22 (or whatever

minumum is).

Now reverse your lens (still set wide open) and hold it in front

of the camera mount. The reported shutter speed should be about

another 2 stops lower. This is because you are now at about lifesize

magnification, which loses 2 stops of light. This is what the

camera will do if you have a reversing ring without the pin.

Two stops (approx) lower than the very first reading is what

the camera would do with a reversing ring that has the pin.

I agree that changing the aperture will affect the shutter speed

reading in all these cases. But in the reversed case with no

adapter (or adapter with no pin) the camera is reporting the wrong

shutter speed and will overexpose your shots (except for TTL flash

as I mentioned earlier).

Scott, if you have a screw mount adapter it should have some sort

of pin too, to hold the aperture sensing lever at the wide open

position. That should tell you were you would need to add a pin.

Greg

Scott,

My pin-less one came from B&H. Got it when my real one was

stolen and the local stores couldn't get me a Pentax replacement.

I didn't know about the pin issue either until I tried to use it.

Without the pin the camera thinks the lens is stopped down all

the way. So you have enough light coming through the lens for 1/125

and the camera says 2 seconds because it expects the lens to stop

down a lot during exposure.

With the pin the camera expects the light to stay the same during

exposure so whatever you set the lens aperture to works fine.

TTL flash will work without the pin since it meters during

the shot. Otherwise I think they aren't very useful. I considered

adding a pin to mine but found a used Pentax one before I got

around to it.

Good luck - Greg

The genuine Pentax reversing ring has a pin that pushes the

aperture sensing lever in the body to the "wide open" position.

So the (most) cameras will meter properly.

I had a 3rd party reversing ring at one time (was black anodized

aluminum, not stainless steel looking like Pentax ones). It didn't

have the pin so the camera thought you were shooting at minimum

aperture and picked a very slow shutter speed. It was basically

useless for how I wanted to use it.

I eventually found a real Pentax one (to replace my stolen one)

and now I can shoot the way I want.

Greg

Searching for "interference patterns in aurora photos" on google

got me <a href="http://216.239.57.104/search?q=cache:DMTd7PECHFgJ:www.ptialaska.net/~hutch/aurora.html+interference+patterns+in+aurora+photos&hl=en&ie=UTF-8">this hit</a>.

<p>

Sounds like your filter is the problem.

<p>

The second hit is a similar discussion to this one on none other

than photo.net.

<p>

Greg

DSLRs don't have live display on the LCD due to the mirror,

shutter and generally the sensors used don't support video.

It still could be useful: take the shot over your head, look at

the LCD, shoot again if necessary.

Greg

You can see interference patterns like this if you are ever

in a restaraunt or bar at night and they have neon light signs

inside. Look at the reflections of the sign in a window and you

can see the interference patterns caused by the reflections off the

inside and outside surface of the glass. This happens because the

neon light is fairly monochromatic (just like your green northern

lights I'd guess).

I used to make holograms (which is all about interference patterns)

and so I tend to look for them in normal life.

Greg

I think you have tested the optical flatness of your camera's AA

filter. The aurora light is probably single freqency so you are

seeing interference patterns between the top and bottom surfaces.

If you have a filter on the camera (especially if it's uncoated)

then that is a suspect too.

Greg

You're welcom Tony.

An easy viewer to start with might be the Viewmagic. It's

made to view 4x6 prints in an over/under format. It has no

lenses just some front surface mirrors. So the magnification

isn't high but the image quality is good because there are no

cheap lenses in the path. Steve Berezin (link on my page) sells them

for $33. Now that I think about it, they could be used to view

6x7 slides full frame on a light box. Not high magnification but

you'd have a quick way to try out 3d slides. Then you could decide

on an MF viewer or build a Wheatstone viewer if you want to stay

with 6x7. (Don't worry about prisms for now.)

Greg

You can make good shots using a slide bar (shoot, shift, shoot)

or handholding using the weight shift method. Put your weight on

your left leg, take first shot, shift your weight to your right

leg and take second shot. This will give a shot with a separation

roughly equal to eye spacing.

This works best for things that don't move. With trees in the wind

or people you will often get what is called retinal rivalry. Where

parts of the image don't work in stereo. For example if you take

stereo shots from the window of an airplane (using a motor drive

camera) the cars on a road going one direction will look like they

are floating in the air. The ones going the opposite direction will

look like a car shaped hole pushed into the road.

As to film: I shoot a lot of Velvia. 3D makes film grain more visible

because it doesn't match for each eye. That is what pushed me from

35mm stereo to MF stereo. Like I said I shoot a lot of Velvia, plus

E100SW and even a bit of (B&W) Scala. I find most films good enough

for MF stereo. You may still detect grain in the featureless sky

but in the detailed image there won't be any.

Have fun - Greg

B&H now shows the price at $1499 (if you click on the $1699

price which is a link).

I should mention that viewing MF slides in a good viewer is the

best from of stereo (IMO).

With 35mm or viewmaster you have small images or film grain.

With prints you (often) have glare or uneven lighting on the two

images. And prints can't show the contrast ratio of a slide.

Projection lets lots of people view at once, but tends to look dim

(unless you own an Imax 3d projector :-) and there can be crosstalk

between eyes due to the limited cutoff of the polarizers. LC shutter

glasses and a computer monitor can look pretty good but there are

crosstalk issues (due to phosphor decay) or flicker issues (if you

lower the refresh rate to reduce the cross talk).

MF stereo also allows orthoscopic viewing with regular achromats.

Orthoscopic means the original angles in the scene are reproduced

when viewing. With slides that means viewing with the same FL lens

as the camera used. With 35mm film it is difficult to get a 35mm

FL lens of sufficient diameter without going to an expensive loupe.

So most 35mm viewer (Realist etc) use longer FL lenses (hence lower

magnification) than the corresponding camera, which leads to stretch (where the depth dimension is

stretched). Stretch may seem good until you see someone's arm in

a 3d shot s t r e t c h e d toward the camera. (To be fair, some

people like this effect within reason).

With MF stereo you can shoot with a 75 or 80mm camera lens. You can

get achromats in the 80mm range by 40mm diameter which will work

well for a viewer. Surplusshed.com carries various achromats, many

of which might work well for a viewer if you are into building one.

Greg

I shoot MF stereo primarily. Check out my <a href="http://www.angelfire.com/ca/erker">web page</a> for info on

my home built SR225 (Stereo Ricohmatic 225).

<p>

On rule of thumb is that the nearest object in a stereo scene should

be no closer than 30 times the lens separation of the camera (when

infinity is included in the scene). So if you have wide cameras

it may be difficult to make shots that don't have too much on-film

deviation (i.e. too much depth), unless you shoot from the edge

of cliffs or other spots to control the near subjects.

<p>

Another effect from using wide separation is you end up with what

is called a hyper-stereo. Hyperstereos give you more stereo effect

on far away objects but will cause things to look smaller. If your

separation is 10x your eyespacing then things will look like a 1/10th

scale model. This can be a cool effect for mountains etc but isn't

natural looking.

<p>

If you want to play with MF stereo you could start out with a

Sputnik (Russian MF 3d camera from the 60's). I paid $300 for mine

but thanks to ebay they go for much less now. They only have 3

element lenses but in stereo you usally stop down to get everything

in focus, so they are pretty good at f16 or f22.

<p>

rmm3d.com sells a MF viewer kit (and I think a pre-assembled version)

as well as mounts that fit it. They are stereo mounts (2 openings)

with 50x50mm, 40x50, 50x40, or panoramic sized openings. So you

can crop the shot if you like. With 6x7 film you either have to

shoot all verticals or crop your horizontals since the film is

wider than eyespacing so you can't view 6x7 with simple lenses.

If you wanted to view 6x7 you would have to use lenses with prism

(like old stereoscopes did) or build a Wheatstone viewer (mirrors).

<p>

Let me know if you have any other questions.

<p>

Greg