Nd filters versus stopping down

[xkaes]

Let's go far afield -- from the original simple question -- as we often do!!

[LabRat]

Interesting. You realise that reducing the background light with a ND filter reduces also the star light so their mutual ratio doesn't change, does it?

But stars are very bright point sources, it's that pesky atmosphere and light pollution that's the problem...

Where's contrast when 'ya need it!?!!!

Steve K

[xkaes]

But stars are very bright point sources, it's that pesky atmosphere and light pollution that's the problem...

Where's contrast when 'ya need it!?!!!

Steve K

Like I said, the original question had nothing to do with astro-photography.

[Drew Wiley]

It's already been hinted at, but not all are created equal and can potentially affect sharpness or create a bit of flare just like other cheap filters, esp if stacked. The also can mess with color film due to often having a bit of hue bias.

[Drew Wiley]

...I almost always encountered density labeling, which is logarithmic. Every .30 added up equals a full stop or a EV. Pretty darn simple, even for me. For example, .90 means I count three fingers, equating to either three f-stops I need to open up the lens, or three full steps of less speed on the shutter, unless long time exposures are needed.

[Jac@stafford.net]

You guys are just too much! I shot stars using a 70's Instamatic with a flash cube!
Yea sure, it burned my forehead, damn near blinded me, but with modern gear...

Some amateur said I had the camera turned backwards, but I saw stars!
I STILL see stars.

[Pfsor]

But stars are very bright point sources, it's that pesky atmosphere and light pollution that's the problem...
Where's contrast when 'ya need it!?!!!
Steve K

Really? So why are the stars drowned by the ambient light then? And how does the ND filter helps them if it doesn't change the mutual light ratio between the two??

[Huub]

For me there are two reason to use a ND filter. First is when i want to shoot (nearly) wide open and the fastest shutter speed of the lens i use is way to slow, for instance when using a 360mm tele-xenar for a portrait. That lens is in a synchro-compur 3 of which i don't trust the fastest speed, so i try to keep it over 1/60 sec. The second reason for using ND-filters is when taking pictures of slow moving rivers, lakes and ponds where i want to create a wash out effect in the water. This calls for speeds of 30 seconds and beyond, which will be hard to reach by stopping down in broad day light.

[tonyowen]

Thank you all for your views.

Therefore, my understanding is :-
1] Given the optimal (recommended/preferred) aperture for large format images seems to be f16 or f22
2] Given a lens with a large aperture but no diaphragm.
Then I could use ND filtration on the lens to give an effective f16/f22 setting and use the appropriate speed for that pseudo f16/f22 lens aperture.
[Again I'm ignoring the effects of the ND filtration on the image due to its manufacturing characteristics, and the difficulties of focusing through high ND filtration]
Right or wrong???????
Regards
Tony

[Pfsor]

Thank you all for your views.

Therefore, my understanding is :-

Then I could use ND filtration on the lens to give an effective f16/f22 setting and use the appropriate speed for that pseudo f16/f22 lens aperture.

Tony

You would not get an effective f16/f22 aperture setting. You would just reduce the light to the value of those aperture settings. Those are two different things.