Catching the ISS with a 400 2.8 IS + 5.6x worth of TCs :)

Wow!

Awsome, I was wondering how many pics were culled to get that and then read 121, great stuff

This may show my n00bness to astrophotography but....why F22?

Sdiver2489 wrote in post #12244536
This may show my n00bness to astrophotography but....why F22?

With all the TCs the max aperture would've been F/16 I think, so F/22 is only one stop down from wide open.

Nicely Captured!

Great shot with excellent timing.

Thank you all for the comments!

funkyfones wrote in post #12244506
Awsome, I was wondering how many pics were culled to get that and then read 121, great stuff

Yes, I shot 121 frames to get this one. About 15% are sharp enough, and the posted photo was the best of the 15%. Assuming focus was nailed, there are two other external variables that influence the sharpness - panning shake and the "wavy" atmospheric turbulence. I turn on IS to mitigate the shake. Shooting many frames increases the chances of getting through where the air turbulence is least.

I'd have shot more frames if the 7D doesn't slow down in fps at low light scenes.

phreeky wrote in post #12247745
With all the TCs the max aperture would've been F/16 I think, so F/22 is only one stop down from wide open.

Yes, the 2263 mm combo has a maximum Av of f/16. I stopped down 1 stop to f/22 to lessen the aberrations of all that glass.

liquidstone wrote in post #12247988
Thank you all for the comments!



Yes, I shot 121 frames to get this one. About 15% are sharp enough, and the posted photo was the best of the 15%. Assuming focus was nailed, there are two other external variables that influence the sharpness - panning shake and the "wavy" atmospheric turbulence. I turn on IS to mitigate the shake. Shooting many frames increases the chances of getting through where the air turbulence is least.

I'd have shot more frames if the 7D doesn't slow down in fps at low light scenes.



Yes, the 2263 mm combo has a maximum Av of f/16. I stopped down 1 stop to f/22 to lessen the aberrations of all that glass.

I got the max aperture, but didn't know if you were listing the aperture the lens was set to or the aperture of the entire string. Stopping down to avoid aberrations is a valid concern...didn't think of that. I just wonder if the loss of sharpness from stopping it down that little bit was worth the benefit. Most lenses take a pretty big hit as they get towards F22-F32. Regardless, cool shot!

Sdiver2489 wrote in post #12248949
I got the max aperture, but didn't know if you were listing the aperture the lens was set to or the aperture of the entire string. Stopping down to avoid aberrations is a valid concern...didn't think of that. I just wonder if the loss of sharpness from stopping it down that little bit was worth the benefit. Most lenses take a pretty big hit as they get towards F22-F32. Regardless, cool shot!

I normally list the Av of the "entire thing" regardless of what's reported in the EXIF (EXIF says f/8 in this case since only the first 2x TC was seen by the camera).

Yes, certainly there is some diffraction effects at f/22. However, for this particular combo, the reduction of aberrations due to stopping down outweighs the softening effect of diffraction. Thus, there is a net gain in IQ improvement.

How do I know? As a matter of practice, I test my various birding combos under controlled conditions to find out the sweet Av before using such gear afield. My 7D + 400 2.8 + 5.6x is sharper at f/22 than at wide open (f/16).

liquidstone wrote in post #12249114
I normally list the Av of the "entire thing" regardless of what's reported in the EXIF (EXIF says f/8 in this case since only the first 2x TC was seen by the camera).

Yes, certainly there is some diffraction effects at f/22. However, for this particular combo, the reduction of aberrations due to stopping down outweighs the softening effect of diffraction. Thus, there is a net gain in IQ improvement.

How do I know? As a matter of practice, I test my various birding combos under controlled conditions to find out the sweet Av before using such gear afield. My 7D + 400 2.8 + 5.6x is sharper at f/22 than at wide open (f/16).

By all means I trust you, I was more curious than anything else. As you can see, I have not even a single teleconverter and barely have what qualifies as a telephoto lens, so I'm definitely no expert. I've taken a grand total of two astrophotography shots of which one turned out decent. Great shot and keep up the good work!

Awesome work Romy.

AdamJL wrote in post #12249299
Awesome work Romy.

Thanks, Adam!

liquidstone wrote in post #12249114
I normally list the Av of the "entire thing" regardless of what's reported in the EXIF (EXIF says f/8 in this case since only the first 2x TC was seen by the camera).

Yes, certainly there is some diffraction effects at f/22. However, for this particular combo, the reduction of aberrations due to stopping down outweighs the softening effect of diffraction. Thus, there is a net gain in IQ improvement.

How do I know? As a matter of practice, I test my various birding combos under controlled conditions to find out the sweet Av before using such gear afield. My 7D + 400 2.8 + 5.6x is sharper at f/22 than at wide open (f/16).

Slightly off-topic, but...most lenses start suffering from diffraction ~f/11.. some f/16, but with the 5.6x TC's on, it shouldn't(technically) start to show until much smaller aperture? Ie: 400mm@ f/22 would be an ~18mm diaphragm opening. 5.6x400..2240mm @f/22 would be a ~102mm diaphragm opening, and the same ~18mm opening would equal ~f/124(f/128). Would the diffraction..from light bending, not occur at the same diaphragm size, no matter the relation to FL?

1Tanker wrote in post #12255456
Slightly off-topic, but...most lenses start suffering from diffraction ~f/11.. some f/16, but with the 5.6x TC's on, it shouldn't(technically) start to show until much smaller aperture? Ie: 400mm@ f/22 would be an ~18mm diaphragm opening. 5.6x400..2240mm @f/22 would be a ~102mm diaphragm opening, and the same ~18mm opening would equal ~f/124(f/128). Would the diffraction..from light bending, not occur at the same diaphragm size, no matter the relation to FL?

Good point, but a common misconception on diffraction with TC'ed lenses.

The effect of diffraction is the same at any given f-stop or Av (which is a function of focal length and aperture size). It doesn't matter how that focal length is achieved, whether native or with TCs.

Here's a link to a longer but quite simple explanation on this. Scroll down to the bottom of the page to read the Technical Note if you don't wish to wade through the whole article.

http://www.cambridgein​colour.com …ffraction-photography.htm

Incredible!