reason # 43 for the 12-40mm/2.8 - Astral Photography

Started 3 months ago | Photos
drpoop
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reason # 43 for the 12-40mm/2.8 - Astral Photography
3 months ago

I am no more than an enthusiast, but I enjoy attempting to snag astral shots when I can.

I had many reasons to grab the 12-40mm, but among them was the f 2.8 aperture at 12mm to give me just that extra bit of light and a somewhat wide field. With a bit of LR tweaking, I'm quite please with this capture of the milkyway.

alternatively, I used my 7.5 mm f 3.5 FE to grab this shot. It's not the best composition, but is an example of how f 3.5 (even with 30 sec exposure vs 25 sec at 12mm) doesn't grab as much detail as f 2.8

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Bob Tullis
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That's rather a stretch
In reply to drpoop, 3 months ago

Neither lens can replace the other.  If you want the best detail for wide field astro tomorrow night, the 12-40 becomes a dud.

Not to rain on your 12-40/2.8 parade - the enthusiasm is well understood.  

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drpoop
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Re: That's rather a stretch
In reply to Bob Tullis, 3 months ago

Bob Tullis wrote:

Neither lens can replace the other. If you want the best detail for wide field astro tomorrow night, the 12-40 becomes a dud.

True. I didn't mean that one replaces the other... just that I am glad to get that extra stop of light to make my efforts (at 12mm) a bit more bright to allow me to pull greater detail.

What I'd really like... is a 9mm f 2.8 for under $400.

Not to rain on your 12-40/2.8 parade - the enthusiasm is well understood.

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...Bob, NYC
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Bob Tullis
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Re: That's rather a stretch
In reply to drpoop, 3 months ago

drpoop wrote:

Bob Tullis wrote:

Neither lens can replace the other. If you want the best detail for wide field astro tomorrow night, the 12-40 becomes a dud.

True. I didn't mean that one replaces the other... just that I am glad to get that extra stop of light to make my efforts (at 12mm) a bit more bright to allow me to pull greater detail.

What I'd really like... is a 9mm f 2.8 for under $400.

There's a lot of folks ahead of the both of us, in that line (despite the potential for such a lens to be a dog).    

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CrisPhoto
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Re: reason # 43 for the 12-40mm/2.8 - Astral Photography
In reply to drpoop, 3 months ago

drpoop wrote:

alternatively, I used my 7.5 mm f 3.5 FE to grab this shot. It's not the best composition, but is an example of how f 3.5 (even with 30 sec exposure vs 25 sec at 12mm) doesn't grab as much detail as f 2.8

Very good shot of the milky way, in my area there is to much light pollution for this.

While I share your enthusiasm with astro and the 12-40 as well, one little remark:

The difference you observe between 12/f2.8 and 7.5/f3.5 is not the aperture alone. It is the difference in light gathering area.

The difference is like this:

  • 12mm, f2.8: =>entrance diameter 12mm/2.8=4,2mm => entrance area = 18mm²
  • 7.5mm, f3.5:=>entrance diameter 7.5mm/3.5=2,1mm => entrance area =4.5mm²

As you already observed, the 12/2.8 gathers 4 times (400%) more light from the distant star while the aperture value is only 25% "bigger".

Christof

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biza43
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Re: reason # 43 for the 12-40mm/2.8 - Astral Photography
In reply to drpoop, 3 months ago

These are good shots. Just a recommendation, try to apply a bit of colour noise reduction, your shot has a lot of green and purple blotches.

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Paul Kersey Photography
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Re: reason # 43 for the 12-40mm/2.8 - Astral Photography
In reply to drpoop, 3 months ago

drpoop wrote:

I am no more than an enthusiast, but I enjoy attempting to snag astral shots when I can.

I had many reasons to grab the 12-40mm, but among them was the f 2.8 aperture at 12mm to give me just that extra bit of light and a somewhat wide field. With a bit of LR tweaking, I'm quite please with this capture of the milkyway.

alternatively, I used my 7.5 mm f 3.5 FE to grab this shot. It's not the best composition, but is an example of how f 3.5 (even with 30 sec exposure vs 25 sec at 12mm) doesn't grab as much detail as f 2.8

Nice shots irrespective of chroma noise. I don't have the patience for astrotography, especially with handholding.

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drpoop
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Re: reason # 43 for the 12-40mm/2.8 - Astral Photography
In reply to CrisPhoto, 3 months ago

CrisPhoto wrote:

drpoop wrote:

alternatively, I used my 7.5 mm f 3.5 FE to grab this shot. It's not the best composition, but is an example of how f 3.5 (even with 30 sec exposure vs 25 sec at 12mm) doesn't grab as much detail as f 2.8

Very good shot of the milky way, in my area there is to much light pollution for this.

While I share your enthusiasm with astro and the 12-40 as well, one little remark:

The difference you observe between 12/f2.8 and 7.5/f3.5 is not the aperture alone. It is the difference in light gathering area.

The difference is like this:

  • 12mm, f2.8: =>entrance diameter 12mm/2.8=4,2mm => entrance area = 18mm²
  • 7.5mm, f3.5:=>entrance diameter 7.5mm/3.5=2,1mm => entrance area =4.5mm²

As you already observed, the 12/2.8 gathers 4 times (400%) more light from the distant star while the aperture value is only 25% "bigger".

Christof

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Hey, thanks for the detailed explanation. Its handy to know the math behind it.

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drpoop
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Re: reason # 43 for the 12-40mm/2.8 - Astral Photography
In reply to biza43, 3 months ago

biza43 wrote:

These are good shots. Just a recommendation, try to apply a bit of colour noise reduction, your shot has a lot of green and purple blotches.

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www.paulobizarro.com

Thanks for the comments. I'll go back to my RAW file and try to tweak it to remove the color noise a bit more.

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drpoop
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Re: reason # 43 for the 12-40mm/2.8 - Astral Photography
In reply to Paul Kersey Photography, 3 months ago

Paul Kersey Photography wrote:

drpoop wrote:

I am no more than an enthusiast, but I enjoy attempting to snag astral shots when I can.

I had many reasons to grab the 12-40mm, but among them was the f 2.8 aperture at 12mm to give me just that extra bit of light and a somewhat wide field. With a bit of LR tweaking, I'm quite please with this capture of the milkyway.

alternatively, I used my 7.5 mm f 3.5 FE to grab this shot. It's not the best composition, but is an example of how f 3.5 (even with 30 sec exposure vs 25 sec at 12mm) doesn't grab as much detail as f 2.8

Nice shots irrespective of chroma noise. I don't have the patience for astrotography, especially with handholding.

Thanks

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CrisPhoto
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Re: reason # 43 for the 12-40mm/2.8 - Astral Photography
In reply to drpoop, 3 months ago

drpoop wrote:

CrisPhoto wrote:

drpoop wrote:

alternatively, I used my 7.5 mm f 3.5 FE to grab this shot. It's not the best composition, but is an example of how f 3.5 (even with 30 sec exposure vs 25 sec at 12mm) doesn't grab as much detail as f 2.8

Very good shot of the milky way, in my area there is to much light pollution for this.

While I share your enthusiasm with astro and the 12-40 as well, one little remark:

The difference you observe between 12/f2.8 and 7.5/f3.5 is not the aperture alone. It is the difference in light gathering area.

The difference is like this:

  • 12mm, f2.8: =>entrance diameter 12mm/2.8=4,2mm => entrance area = 18mm²
  • 7.5mm, f3.5:=>entrance diameter 7.5mm/3.5=2,1mm => entrance area =4.5mm²

As you already observed, the 12/2.8 gathers 4 times (400%) more light from the distant star while the aperture value is only 25% "bigger".

Christof

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OM-D + Sam7.5, PL25, O60, O75
P12-35, O75-300

Hey, thanks for the detailed explanation. Its handy to know the math behind it.

Thanks too.

Oh, and as you mention maths, ups, I calculated square instead of circle. The area is d*d*pi/4. But anyhow, the stars remain the same and the brightness difference of 400% too ...

Christof

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