What Speed to arrest the moons movement?

[Stagecoach]

I seem to recall that there is an 'advised' shutter speed based upon FL (focal length) being used that you should not go below otherwise you will see the movement of the moon in an image.

Does anyone know this, please?

I have searched for this info but can not find it, just lots about exposure, which is not my concern.

The moon moves at a rate equivalent to its diameter in two minutes (near enough) and movement blur would be noticeable in an image the greater the size of the magnification (FL) I believe.

Right, the reason for the question is that I want to have that knowledge so that when I'm in a position where I have the option to undertake a long exposure (dim moon, NDs, GNDs) I know what speed I must not go below.

Thanks in advance.

Grahame

[James G]

Grahame,
not sure I this will help but try the attached link...

http://ryanzimmermanphotography.blog...ium-focal.html

I've extracted his 'cheat sheet ' below, but there is a fair bit more explanation of his calculations in the blog...

Exposure Time
Again, I'll offer a cheat-sheet before my derivation:

Nikon D700, APS-C 16.2 mp, with no motion blur:
200mm lens: 1/4s or faster
400mm lens: 1/6s or faster
1250mm lens: 1/20s or faster

Nikon D7100, APS-C 24.1 mp, with no motion blur:
200mm lens: 1/4s or faster
400mm lens: 1/8s or faster
1250mm lens: 1/25s or faster

Nikon D800E, Full frame 36.3 mp, with no motion blur:
200mm lens: 1/4s or faster
400mm lens: 1/8s or faster
1250mm lens: 1/25s or faster

[Stagecoach]

Grahame,
not sure I this will help but try the attached link...

http://ryanzimmermanphotography.blog...ium-focal.html

I've extracted his 'cheat sheet ' below, but there is a fair bit more explanation of his calculations in the blog...

Many thanks James,

This is what I was after and the 'cheat sheet' is ideal. I'll leave the calculations for now and trust he knows what he is talking about far more than my ability to actually understand them

[James G]

Glad it helps.

[IzzieK]

This article is the guide that I use...

http://www.wikihow.com/Photograph-the-Moon

[Brownbear]

Hi Grahame,

Here is an article on photographing the moon as part of a landscape scene which includes some interesting info on the positioning and best time to photograph such a scene.

http://garyhartblog.com/photo-tips/full-moon/

[george013]

Grahame,
not sure I this will help but try the attached link...

http://ryanzimmermanphotography.blog...ium-focal.html

I've extracted his 'cheat sheet ' below, but there is a fair bit more explanation of his calculations in the blog...

Intresting subject.
In this mentioned article the D7000 is often called D700.
There is another question I have: do you have to 'correct' the focal length for a cropcamera? Do you have to recalculate a 400mm full frame to 600mm aps-c. Emotional ( is that the right word for it?) I would say yes, but when I think about it I would say it doesn't make any difference.

George

[Stagecoach]

This article is the guide that I use...

http://www.wikihow.com/Photograph-the-Moon

Hi Izzie,

Thanks for the link,

For info the article gives reasonable basic advice on shooting the moon but does not touch on the 'speed to arrest movement' other than the generalized comment 'Exposure time should be short and it's usually best to photograph the full moon'.

From what I have always understood to take a basic shot of the moon, a full moon is not the best time. This being due to the light on its surface making it somewhat flat, not so important if the moon is just a tiny part of your image such as in mine but more significant if you are using a long FL and looking for those craters.

Going back to my 1st image here of which I achieved in one exposure, and of which there is only one day per month that image could be produced with one exposure, if I had of used a longer exposure (to smooth the water by adding an ND filter) and lets say an exposure of 30 seconds we would have seen a moon that was the same width but one and a half times longer like a small sausage

Grahame

[Stagecoach]

Hi Grahame,

Here is an article on photographing the moon as part of a landscape scene which includes some interesting info on the positioning and best time to photograph such a scene.

http://garyhartblog.com/photo-tips/full-moon/

Hi Christina,

Thanks for that useful link, I now have a small collection and am using them to build my knowledge in this area.

As always I tend to jump into something new with limited knowledge, build a database of real life 'trial' images to start my own conclusion process, then start the more serious reading coming to the conclusion I could have read this earlier and saved some time

Grahame

[Brownbear]

You're most welcome. One day I will try to photograph a scene like this and I have no doubt your thread will stand me in good stead.

Indeed, I can relate to that too, well. I've ordered a bunch of books on Chinese water colours, just learned that one actually paint using Photoshop (not that I have ever painted anything in real life since grade 2), and I have yet to find an article on photographing soap bubbles BUT I filled the frame with a soap bubble yesterday morning!

Hi Christina,

Thanks for that useful link, I now have a small collection and am using them to build my knowledge in this area.

As always I tend to jump into something new with limited knowledge, build a database of real life 'trial' images to start my own conclusion process, then start the more serious reading coming to the conclusion I could have read this earlier and saved some time

Grahame

[James G]

George...

There is another question I have: do you have to 'correct' the focal length for a cropcamera? Do you have to recalculate a 400mm full frame to 600mm aps-c. Emotional ( is that the right word for it?) I would say yes, but when I think about it I would say it doesn't make any difference.

Take a look at the table below (it is not quite accurate for the moon) but it gives you an idea of the corrections you would need to apply with a crop sensor, rather than full frame.

Seconds Before Stars Blur
Focal Length, Full Frame, Nikon 1.5 Crop, Canon 1.6 Crop,
10, n/a, 33, 31,
14, 36, 24, 22,
16, 31, 21, 20,
20, 25, 17, 16,
24, 21, 14, 13,
28, 18, 12, 11,
35, 14, 10, 9,
50, 10, 7, 6,
70, 7, 5, 4,
85, 6, 4, 4,


The formula to use for stars is: Exposure time = 600 / (lens focal length x crop factor)

but it needs to be adjusted to allow for the movement of the moon against the sky as well.

Since I have only shot the moon directly rather than as part of a long exposure landscape, which I believe is what Grahame is considering, it will need someone to sit down and work something more definitive to account for the movement of the moon rather than the stars.
I'll see what I can do .... but it probably won't be quick

(tried formatting the table but couldn't get it to work... )

[James G]

Grahame,

As always I tend to jump into something new with limited knowledge, build a database of real life 'trial' images to start my own conclusion process, then start the more serious reading coming to the conclusion I could have read this earlier and saved some time

+1

[george013]

George...


Take a look at the table below (it is not quite accurate for the moon) but it gives you an idea of the corrections you would need to apply with a crop sensor, rather than full frame.

Seconds Before Stars Blur
Focal Length, Full Frame, Nikon 1.5 Crop, Canon 1.6 Crop,
10, n/a, 33, 31,
14, 36, 24, 22,
16, 31, 21, 20,
20, 25, 17, 16,
24, 21, 14, 13,
28, 18, 12, 11,
35, 14, 10, 9,
50, 10, 7, 6,
70, 7, 5, 4,
85, 6, 4, 4,


The formula to use for stars is: Exposure time = 600 / (lens focal length x crop factor)

but it needs to be adjusted to allow for the movement of the moon against the sky as well.

Since I have only shot the moon directly rather than as part of a long exposure landscape, which I believe is what Grahame is considering, it will need someone to sit down and work something more definitive to account for the movement of the moon rather than the stars.
I'll see what I can do .... but it probably won't be quick

(tried formatting the table but couldn't get it to work... )

Take a D800, I think you can use it as a crop-camera. Does the image move different across the sensor if you use it as a full frame or a crop camera? It's the same camera and the same lens.

George

[James G]

Sorry George, not sure I understand your question with respect to D800. I'm a Canon user but I believe the D800 is a full frame camera. I can't imagine how it could behave like a cropped sensor device. (My 7D for instance).

Basically, as I understand it, because a cropped sensor is physically smaller than a full frame sensor the motion of stars, moon etc is correspondingly faster through the field of view, hence the need to recalculate the minimum exposure time to avoid streaking/blur .

The table above just shows the different minimum exposure times for each sensor type, so only the full frame exposure times apply for a D800. I would use the 1.6 values for my 7D.

James

[Rebel]

Some good info here, thanks to all the contributors.

[Donald]

Basically, as I understand it, because a cropped sensor is physically smaller than a full frame sensor the motion of stars, moon etc is correspondingly faster through the field of view, hence the need to recalculate the minimum exposure time to avoid streaking/blur .

Not sure If I'm misunderstanding something here, but whilst the time taken for the object to travel from one side of the field of view to the other will be shorter with the crop frame, because of the smaller sensor size, the speed at which the object is travelling across the field of view is exactly the same irrespective of the field of view.

The moon doesn't travel faster because it knows that someone's looking at it with a crop frame camera.

[James G]

George,
my apologies, I should have looked at the detailed tech spec of the D800....
It is a full frame sensor but can be set to mimic a 1.5 crop factor (d7000). I think regardless of this you would use the full frame figures. (see the note to Donald below. )

Donald,
I was being too simplistic in my explanation so apologies to you too....
I think the issue is really to do with how long it takes for star trails to develop. i.e. what is the maximum exposure time possible before a source, (stars as pinpoint sources are a bit easier to envisage), is recorded by more than one pixel.
On a sensor with a larger physical footprint, and I assume a larger pixel size, there is a longer exposure time. This leads me to surmise that in answer to Georges query about the D800 the rules for a full frame sensor apply regardless of the optional 1.5 crop mode because the physical size of the sensor and the pixel size does not change!


My brain now hurts with trying to think all this through and explain it properly? If I have not, I'm guessing there are going to be a lot CiCs members correcting me.

James

[george013]

Sorry George, not sure I understand your question with respect to D800. I'm a Canon user but I believe the D800 is a full frame camera. I can't imagine how it could behave like a cropped sensor device. (My 7D for instance).

Basically, as I understand it, because a cropped sensor is physically smaller than a full frame sensor the motion of stars, moon etc is correspondingly faster through the field of view, hence the need to recalculate the minimum exposure time to avoid streaking/blur .

The table above just shows the different minimum exposure times for each sensor type, so only the full frame exposure times apply for a D800. I would use the 1.6 values for my 7D.

James

I have a FF camera and a 400mm FF lens pointing to the moon. The moon moves over my sensor with a speed of x mm/sec. That speed will be the same on the full part of the sensor as on a cropped part of the sensor. Off course the moon will reach the limits of the cropped part earlier than the full part since it's smaller.
So I doubt if you have to correct the focal length for a crop camera.

George