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Archive 2020 · Sigma 24-70 F2.8 for Sony - Field Curvature (especially at close distance)

  
 
GMPhotography
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p.2 #1 · p.2 #1 · Sigma 24-70 F2.8 for Sony - Field Curvature (especially at close distance)


pulper11 wrote:
Thanks for your reply. My understanding of this concept is limited, to say the least. However, according to the link above from photographylife.com, it isn't going to happen.

"Unfortunately, it is impossible to fix field curvature in post-production software such as Photoshop and Lightroom."

Better to know that now than later.


That’s actually wrong. I’ve done this many times fixing distortion in post with raw converters and even photoshop using lens profiles. Here is a test with the Sony 35 1.8 the first 4 or 5 posts are directly retaliated to this.now I’m on a tripod and imperfectly level this is all lens . I have many samples like this with all sorts of lenses. I work with C1 but you can do this in photoshop as well. Remember this is not about tilting the lens up or down and dealing with keystoning that’s another issue that actually can be fixed.ill look at that link just to be sure we are talking the same thing. For clarity this is all in post


https://www.fredmiranda.com/forum/topic/1616382/#15002855

See if I have another lens test where I show this. It’s a typical test I always do



Apr 23, 2020 at 03:15 PM
GMPhotography
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p.2 #2 · p.2 #2 · Sigma 24-70 F2.8 for Sony - Field Curvature (especially at close distance)


Another sample .here I corrected in Photoshop

https://www.fredmiranda.com/forum/topic/1540668/0?keyword=Big,bronco#14438825


Actually it was C1 and watch the 24-105 it’s really obvious the fix



Apr 23, 2020 at 03:23 PM
Phillip Reeve
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p.2 #3 · p.2 #3 · Sigma 24-70 F2.8 for Sony - Field Curvature (especially at close distance)


GMPhotography wrote:
That’s actually wrong. I’ve done this many times fixing distortion in post with raw converters and even photoshop using lens profiles. Here is a test with the Sony 35 1.8 the first 4 or 5 posts are directly retaliated to this.now I’m on a tripod and imperfectly level this is all lens . I have many samples like this with all sorts of lenses. I work with C1 but you can do this in photoshop as well. Remember this is not about tilting the lens up or down and dealing with keystoning that’s another issue that actually can be fixed.ill
...Show more
I think you two are talking about different issues: Field Curvature (the plane of focus isn't a plane) which can't be fixed in post and distortion (straight lines aren't straight) which of course can be corrected.




Apr 23, 2020 at 03:26 PM
GMPhotography
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p.2 #4 · p.2 #4 · Sigma 24-70 F2.8 for Sony - Field Curvature (especially at close distance)


Phillip Reeve wrote:
I think you two are talking about different issues: Field Curvature (the plane of focus isn't a plane) which can't be fixed in post and distortion (straight lines aren't straight) which of course can be corrected.




Yea I saw the word distortion from OP so was not exactly sure myself either but hey we learn something. Lol

Well I may have misread his initial thoughts.it was early morning for me. Maybe 2 espressos short of normal.



Apr 23, 2020 at 03:54 PM
bobby350z
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p.2 #5 · p.2 #5 · Sigma 24-70 F2.8 for Sony - Field Curvature (especially at close distance)


pulper11 wrote:
I'm not sure what the MFD is on the lens. I agree with you that the bill looks pretty bad. However, I should say that my bigger concern (especially based on people writing in here) is the more real world examples that Dustin shows in the Youtube video that I posted a link to right where he discusses the focusing issues. I do find that I would be taking pictures similar to the ones he's showing here, and it concerns me how bad those pictures look.



Just watched the video. Looks something wrong with the lens. I am not sure how he saying Sigma better than Tamron. Honestly I have given up on youtube reviewers. Best is buy the stuff yourself, test it on how you going to use it and then decide. And it does take a while to get used to it or put stuff through its paces. I have had issues with Sigma AF from my Canon days. During the holidays I end up buying Sigma 105mm f1.4. At start I had hard time nailing shots and I am no stranger to heavy lenses. But now I get much better results. AF is not as I had hoped for but I don't have Sony 135mm f1.8 or any faster focussing primes say like 400mm f2.8 to compare with. My body A7rIV.



Apr 23, 2020 at 08:33 PM
hasenbein
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p.2 #6 · p.2 #6 · Sigma 24-70 F2.8 for Sony - Field Curvature (especially at close distance)


Well, I think other lens developers would simply have made the MFD longer (i.e. made the focusing mechanism hit the hard stop earlier). Seems Sigma wanted to incorporate a low MFD (for marketing reasons?) so hard that they decided to disregard the dismal results at the long end.


Apr 24, 2020 at 12:07 AM
Sinasina
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p.2 #7 · p.2 #7 · Sigma 24-70 F2.8 for Sony - Field Curvature (especially at close distance)


It's not bad if you stop it down though. Look at other manufactures, how many fast prime lenses perform nearly as bad (or sometimes worse) at infinity wide open, the answer is don't shoot them wide open at infinity. This is the same, don't shoot it wide open at the MFD.


Apr 24, 2020 at 01:28 AM
Matti6950
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p.2 #8 · p.2 #8 · Sigma 24-70 F2.8 for Sony - Field Curvature (especially at close distance)


Close focus is much harder then far focus. Wide open is much worse then stopped down. Zooms are worse then primes.

Imo buy a prime or go home And if you still want a zoom then be ready to take any of these disadvantages wich you.

At long distance the Sigma 24-70mm dg dn is sharper then Sony gmaster, especially 70mm, wide open the different is even bigger. I don't use close focus enough to care for the softness it creates, but i know from my nikon 24-70mm VR, that you should expect softer result (but not terrible images).

Also the 70mm focal length of the sigma is supposed to be bad at close focus guys! It's 24mm that has the minimum focus distance NOT 70mm. When designing the lens they must have noted it was easier to keep the good design, by letting the mfd be on 24mm.

For this class of lens however, complaining about anything in the Sigma 24-70mm art is stupid. It's one of the best 24-70mm's i used, it's the cheapest by a mile, and still has some advantages over it's double priced peers, including image quality aspects. I now have both Sigma and GM, and i think i will keep the Sigma. And mind you: i don't mind wich i keep or the money left over by either. Just wanted the best 'all-in-one' lens (possible, i'm very realistic in my expectations to standard zooms). Sigma delivered (and then some for such price).



Apr 24, 2020 at 09:19 AM
TravelinBriNY
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p.2 #9 · p.2 #9 · Sigma 24-70 F2.8 for Sony - Field Curvature (especially at close distance)


Can you unpack your comments a bit more? Why would you keep the Sigma over the Sony?

Sigma is sharper at distance, how are they at 70/2.8 for portraits?



Apr 25, 2020 at 09:58 AM
Douglas L
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p.2 #10 · p.2 #10 · Sigma 24-70 F2.8 for Sony - Field Curvature (especially at close distance)


I just took some pictures with the Sigma this morning. This one is at 70mm and f2.8, but not quite at the MFD.

_DGL5755 by Douglas Liu, on Flickr


_DGL5816 by Douglas Liu, on Flickr



Apr 25, 2020 at 10:09 AM
SoundHound
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p.2 #11 · p.2 #11 · Sigma 24-70 F2.8 for Sony - Field Curvature (especially at close distance)


There’s good reasons that they make and sell macro lenses. With only one or two exceptions they are all primes and not all of them are their best at infinity either.


Apr 25, 2020 at 12:22 PM
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