Sigma 24-70 2.8 IF EX DG, "Im considering"

Tango

Thanks for looking, and advance thank you's for comments!

I did this image (ignore the watermark, I dont have time to undo it, its lost somewhere on my site...and I simply dont care right now to fix it) anyway, I use a FF camera & Canon f3.5 24mm T/S but Ive discovered to do this type of image better I need f2.8.

so im considering the Sigma 24mm-70 F2.8 IF EX DG ("IF" stands for Internal Focus, apparently there is no external movement to suck in dust?)
and ofcourse only from B&H
http://www.bhphotovideo.com/bnh/controller/home?O=workaround.jsp&A=details&Q=&sku=596257&is=REG#reviews


my question: I hope this makes sense...
with low light images like these where shutter speeds are 15s to 180s, would it be more important to have high dollar glass like a Canon 24mm-70 F2.8?
or, in otherwords, would I see the IQ of the two name brands start to even out or get worse because of the high shutter speeds....
or am I totally ignorant and should be hit on the head with a f/2.8?

basically, will the extra $450 for "L" serve me in this type of photography?

and FWIW, my Sigma 150mm sure seems just as sharp as my "L" lenses so I do have faith in Sigma... (my only complaint is light fall off)

ziggy53

My first question is, what do you wish to accomplish with an f2.8 aperture that you feel would improve the image? (Wonderful image BTW.)

Second question is, how important is edge sharpness to your goal?

Third question, did you need the T&S feature to make that image?

Tango

hey Ziggy

the 2.8 is for the top 1/3 only (for the stars and sky)..
I want zero star movement with brightest stars possible, and I need to limit the exposure time below 15sec, and ISO no more than 1600...
this shot was ISO 3200... to much noise, and still there is star movement.

the bottom rest of the image would be @ f8

edge sharpness is important, but maybe not so much if I think about the theory that edge softness leads the viewer to the center... especially for a big print...(like 60in or so)
so whats everyones opinion on that subject?

T/S was set zero on this image, so I dont know if using the Tilt would have been better or not... that is something I wish I knew more about...
I need to learn if/how shutter speeds for night photography affects DOF...
can anyone link me to some knowledge about that?
anyway, if this shot was a sunset or sunrise I sure would have used the tilt, but honestly it didnt even cross my mind when I was attempting this new technique.....I was concentrating on ISOs, Expos and not falling off a Cliff

Tee Why

Optically, the Sigma is on par with the Canon. The Canon is much better built with a much better AF system. Biggest thing you may see in the image between the two is that the Canon has a cooler color cast while the Sigma has a warmer cast.
Check out photozone and also this review here.
http://www.pbase.com/lightrules/2470exl

IIRC the Canon has weather sealing as well. If the difference in price is worth it or not is a personal question that only you can answer.

Good luck.

ziggy53

I think I understand now. You have combined 2 exposures, one for the foreground and another for the upper sky, and the 2 exposures were merged to create the final exposure.

It almost sounds like the EF 24mm, f1.4L USM II could be a great solution for this sort of image. It is awfully sharp in the center at f2 and should give you the sort of exposure duration to stop the stars. It is better to the edges at f8 for the foreground.

Sorry about the price.

Tango

Tee Why wrote:

Optically, the Sigma is on par with the Canon. The Canon is much better built with a much better AF system. Biggest thing you may see in the image between the two is that the Canon has a cooler color cast while the Sigma has a warmer cast.
Check out photozone and also this review here.
http://www.pbase.com/lightrules/2470exl

IIRC the Canon has weather sealing as well. If the difference in price is worth it or not is a personal question that only you can answer.

Good luck.

I dont think I really would put weather sealing to use... but the AF is a issue. I dont care if its slower AF but It needs to be accurate. do you know if this is generally the case? is Sigma AF slow but still just as accurate? or does it hunt and AF at the wrong point?

Tango

ziggy53 wrote:

I think I understand now. You have combined 2 exposures, one for the foreground and another for the upper sky, and the 2 exposures were merged to create the final exposure.

It almost sounds like the EF 24mm, f1.4L USM II could be a great solution for this sort of image. It is awfully sharp in the center at f2 and should give you the sort of exposure duration to stop the stars. It is better to the edges at f8 for the foreground.

Sorry about the price.

Ziggy, sorry I didnt explain better about the shot, yes your right...merged!

and, I cant argue that lens... but the cost would take me another year to save up for... maybe worth the wait?

maybe this Sigma lens will do what I need.... plus zoom to 70mm which is nice too...

dlplumer

:lurk

hawkeye978

Aaron,

You may not be getting what you want with the f/2.8 lens. There are some simple criteria to calculate exposure time to prevent star trails based on the focal length of the lens. You just take 1/lens focal length ( in meters). So if you have a 24mm focal length lens (0.024 meters) then the maximum exposure time to insure you won't get star motion is 1/(0.024 meters) = 41.67 sec. Maybe you can go a little longer depending on you longitude and where you are pointing in the sky. Any exposure longer than that and you are going to begin to resolve motion. Then you have to consider with the larger apertures you aren't going to be as sharp so even if you collect more light with the f/2.8 you may lose resolution. So you were using a f/3.5 and I assume you were running that with a full open aperture then you are gaining 1 f/stop or a factor of two in light collection. So no matter if you have your current 24mm lens or the new 24mm lens you are still limited to that 41.67 sec exposure. The 'better' lens you might get twice the light in for the same exposure, but that 40-50 sec exposure time is probably your limit.

Tee Why

According to Lightrules, who has tested many many lenses. He stated that he's had focusing issues (accuracy) with the Canon lens. He has also returned the Sigma as well to get it calibrated. Generally, AF should be accurate, I don't know of inherent defect in the Sigma 24-70mm lens line. Just the variations you may find in all the lenses.

If you get either of the lens, I would simply tested out to see if it focuses accurately and either return or send it to the maker for repairs.

In dark places, the Sigma may not lock on as easily as the Canon but in terms of accuracy (no back/front focus) I don't think either of the lenses have any inherent problems. Having re-read the reviews, they state that the AF speed is about the same/quick but just noisier.

Tango

hawkeye978 wrote:

Aaron,

You may not be getting what you want with the f/2.8 lens. There are some simple criteria to calculate exposure time to prevent star trails based on the focal length of the lens. You just take 1/lens focal length ( in meters). So if you have a 24mm focal length lens (0.024 meters) then the maximum exposure time to insure you won't get star motion is 1/(0.024 meters) = 41.67 sec. Maybe you can go a little longer depending on you longitude and where you are pointing in the sky. Any exposure longer than that and you are going to begin to resolve motion. Then you have to consider with the larger apertures you aren't going to be as sharp so even if you collect more light with the f/2.8 you may lose resolution. So you were using a f/3.5 and I assume you were running that with a full open aperture then you are gaining 1 f/stop or a factor of two in light collection. So no matter if you have your current 24mm lens or the new 24mm lens you are still limited to that 41.67 sec exposure. The 'better' lens you might get twice the light in for the same exposure, but that 40-50 sec exposure time is probably your limit.

ya this site is specific, im shooting SW and even more South during the winter months. so with this scene (which is not a eazy trip to make) I want to redo using better equipment but dont want to under cut myself if the Sigma will not shine as well in this type of photography, i will spend the extra $450 if needed...
but anyway, using this shot as an example: 15 seconds is max for Zero star rotation. f1.4 Im sure would do me well to use, but f2.8 will keep me under 15 second and I shouldnt need to bump the ISO any higher than 1600....so ya f2.8 will work, and ofcourse f1.4 is "whoa" even better, but the wallet is a factor...

its likely I will just buy the Sigma and try it out somewhere past the light pollution and find out what its got...

Tango

Tee Why wrote:

According to Lightrules, who has tested many many lenses. He stated that he's had focusing issues (accuracy) with the Canon lens. He has also returned the Sigma as well to get it calibrated. Generally, AF should be accurate, I don't know of inherent defect in the Sigma 24-70mm lens line. Just the variations you may find in all the lenses.

If you get either of the lens, I would simply tested out to see if it focuses accurately and either return or send it to the maker for repairs.

In dark places, the Sigma may not lock on as easily as the Canon but in terms of accuracy (no back/front focus) I don't think either of the lenses have any inherent problems. Having re-read the reviews, they state that the AF speed is about the same/quick but just noisier.

thanks for the info, sorry I ran you through that variable, but now that I think about it AF will have "NO" use on this type of shot.. ( I forgot, but manual focus is really the only way to do this shot right, once for the stars and then the FG shot, both using Liveview of course.....)

ziggy53

AaronNelson wrote:

thanks for the info, sorry I ran you through that variable, but now that I think about it AF will have "NO" use on this type of shot.. ( I forgot, but manual focus is really the only way to do this shot right, once for the stars and then the FG shot, both using Liveview of course.....)

I suspect that would be best.

Tango

thanks everyone...!!!

and Ziggy, after reading this review all decisions are off...!
(your to blame! maybe now I will be waiting for tax season to come around to buy a lens)

http://www.the-digital-picture.com/Reviews/Canon-EF-24mm-f-1.4-L-II-USM-Lens-Review.aspx

rookieshooter

FWIW I tried this lens out after sampling the Nikon equivalent and found it to be wanting in focus speed.

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