Originally posted by FozzFoster ...<snip>.. So, my claim that "the new DA* 11-18mm f/2.8 will be the go-to for astro shots" is probably incorrect then, eh?
At what physical aperture would you say is bare minimum for astro?
I've done astro with a kit lens 18mm @ f/3.5 (5.14) with okay results, so the I take it the DA* 11-18mm f/2.8 @ 18mm f/2.8 (6.43) won't be terrible but not the best? Do you think you'd recommend this lens for astro work?
Overall, I really don't think that there is a perfect answer nor a wrong or bad set of answers. There are some better answers than others, but they are all going to need to be viewed/evaluated within a set of constraints of whomever is doing the buying and using....
Quote: Different people have differing opinions, differing needs and approach the trade space considerations with different perspectives and valuations.
The overall evaluation is based on collecting light. For astro / Milky Way - collecting more light is better, which leads to a better overall resulting image (better color, better star resolution, more light, etc.). This is one of the few areas in photography, where gear really does make a difference. Now, having said that - you can really use anything for a lens. You will get an image, and possible a good image.
It all boils down to what set of compromises you are going to make - and only you can make the trade and decision on what you feel is best for you. You are not able to make a decision in this respect without making some compromises. My opinion is all of this is based on how you want to shoot. Here are just a few to get you started....
- Are you going after shooting just a single frame? If just one frame, then you are not going to be using the astrotracker, or any type of tracking mount. This then begs the question of how wide you want to shoot, which will determine the aperture available (fortunately f2.8 is pretty consistently available). This would lead you to wider focal lengths with the largest aperture you can find (10mm/f2.8, 12/f2.8, 14/f2.8, 16/f2, etc.)
- If you are going to use the astrotracker, or a tracking mount, then you will be compositing images (sky and landscape elements) together.
- If you want to collect the greatest amount of available light - then you will probably track (either astrotrack or a tracking mount), and possibly consider stitching. This would lead you to looking at a longer focal length with a larger physical aperture (35/f1.4, 50/f1.4, etc.).
- If cost is a primary concern, then use what you have - or find something that is within you budget - M 28mm/f2.8 can be found for $75 or a M 50mm/f1.7 for $50, or whatever.
These are a few ways of evaluating the problem space to make a decision - but there are plenty of others, too. [Note - I had intended to link to a number of these item in the last post. The Ian Norman - "lonely spec" has an entire series on this topic.]
In the body of the PentaPixel link is a link to this spreadsheet comparison / evaluation set ....
Quote: So, my claim that "the new DA* 11-18mm f/2.8 will be the go-to for astro shots" is probably incorrect then, eh?
No, it's not incorrect at all. At the 18mm end the Sigma 18-35/f1.8 collects substantially more light (f2.8 to f1.8 is 1 1/3 stops faster so almost ~3x more light, and if you calculate the physical open aperture area, I'm guessing probably 4x more actual light). But, that's the (retired) engineer in me. I can certainly see the 11-18/f2.8 doing a very credible job and producing some excellent images.
I had squirreled away $1k for a lens when I bought the K1. It came down to the Sigma 35/f1.4 and the Pentax 15-30/f2.8. I was only going to buy 1 more lens - that's it. The 35/f1.4 had a 2 stop advantage - collecting at least 4x more light (more if you look at the physical open aperture area). But, I also wanted a general wide angle lens for everything else - essentially a multi-purpose lens that was very good for astro/MW. I went with the 15-30 - giving up a substantial amount of light collection in the trade. Yes, a compromise - but, I feel a reasonable compromise. That is the only reason I posted the 3 images above. I finally was able to successfully capture the overall color, width, lighting and overall feeling I wanted - and have been after for several years (and I was still stitching at 15mm). Would the 35/f1.4 have done the job better - absolutely yes, but I would not have had the versatility I really wanted. It would have been more of a one trick pony - be it a really nice pony.
I thought about it for several months - trying a lot of alternatives (the cropped Sigma 18-35/f1.8 on the K1 @ 30mm where you get full frame coverage), and it looked like a patchwork quilt when stitched (some vinginetting). I have a couple of 28/f2.8 lenses that I could have gone with - and I still need to test out (one an old Contax Zeiss 28/f2.8) that I have not gotten around to - as of yet.... But, in many ways - I just wanted to stop testing, and trying - and just go with a proven lens (especially one with no coma). I just want to shoot excellent resulting images.
I email folks at work (well, where I use to work, prior to retirement) images. They want / ask to see them - especially when we go to lunch. I use them as a sounding board. They will crap all over me for poor work. Image #3 from the above set - got an "outstanding - simply blown away" from everyone. And that's only the 3 stitch at 15mm - the actual result that I'm going for is a 3 row 7 image ~ 25 images, stitched and composited all together - that will be able to be printed large. So, I have the right tool set - now I'm only limited by my skill and imagination. I took 150 images that evening 3 weeks ago over 3.5 hours standing out in the desert.
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Quote: Do you think you'd recommend this lens for astro work?
So, to directly answer you question. The 11-18 would not be a bad choice. I have seen excellent results with the 16/f2 in the Astrophotography area. But, for a crop sensor body, I would probably tend to go with the 18-35/f1.8; then the 16/f2; followed by the 11-18/f2.8. Sorta of ranked by the aperture, but also balanced by focal length and overall versatility of the lens. Also,I have not seen any astro shots from the 11-18, so I'm just kind of assuming no coma and it performs overall very well.
Long answer to a short question.... sorry! Also, I'm by no means an expert - I just have an opinion. To see some really fine shots and to get excellent expert opinions (and discussions) - go to the Astrophotography social group (actually - it's a technical group). The folks there produce some really outstanding work.