p.44 #1 · Sigma 14-24mm f/2.8 DG DN first impressions
MAubrey wrote:
It seems possible that the FM post with 14 as the strongest is only at infinity and that 24mm is better at closer distances, since chart testing doesn't measure resolution at infinity.
Certainly it could be. Let's wait to see the forthcoming average MTF at infinity when Roger Cicala tests 10 copies at Lensrentals blog...
I have experienced some sharpness inconsistencies with my unit when working for some recent customers. I'll try to upload an example at 24 mm f8 close focused at 3 meters with the A7 R3. Some precise parts in the right side of the frame were abnormally unsharp, like heavy astigmatism present only in a small part of the frame. I don't really understand this behaviour. But I also didn't have the time to double check for this inconsistency since my commisioned work is my primary concern and it takes all of my time.
p.44 #2 · Sigma 14-24mm f/2.8 DG DN first impressions
Hi
I am having some weird issues with my 14-24 f2,8 DG DN lens. I show you this photograph taken this way:
Sigma 14-24 f2,8 DG DN lens
F7,1@24 mm, 30 seconds exposure, ISO 100, close focusing approx 3-4 meters from the car, remote shutter release (Sony Imaging Edge on a Samsung Tab S3 tablet), sturdy tripod, focus point on the door handle. Sony A7 RIII body.
The weird issue is that the back wheel has clearly a drop in sharpness. Please check the next 100% crops. The first crop shows the front wheel at the left of the frame and the back wheel at the right of the frame. Maybe I am splitting hairs but I see at 100% that the right side is softer (more astigmatic like) than the left side. The car was perfectly parallel to the plane of focus and due to the closed f7,1 f-stop it should be in focus the same as the front wheel:
Both approximately equal, but with some software trick.
I am remembering now that I did not disengaged IBIS when taking the photograph on the tripod. Do you think that IBIS may be responsible for that seemingly shift in focus plane? When I used to shoot with Canon IS lenses on a tripod I always disengaged IS because I knew it would be harmful to the sharpness. But I read somewhere it was not necessary with Sony bodies with IBIS, so I did not turned off.
p.44 #4 · Sigma 14-24mm f/2.8 DG DN first impressions
Hi
I've been testing furtherly my 14-24 DG DN. In my opinion it has noticeable field curvature issues which need to be understood in order to obtain the maximum potential of the lens for corners sharpness.
What I've been testing is different focusing points to maximize corner acuteness. When I focus on dead center, no matter if close or at infinity, corners are not going to be maximally sharp. Only if I select a point of focus toward middle of the right side then the corners are brilliantly acute. Of course that when practicing this focus method then the center is less sharp than when focus point is selected at the center of the frame. But this is a compromise we have to accept to have corners at high level.
Another method is to focus on the center part of the frame and then zoom in with the focus magnifier assistant to check the corners. If they are soft proceed to manually tweak the focus ring slightly and improve them to get tack sharp acuteness and then shoot. When doing this, the center probably will lose some sharpness, but not very much in my view.
When using the Sigma 14-24 DG DN I have decided to disengage IBIS permanently in the camera body to avoid weird issues of drops in sharpness along random parts of the frame. Always off, no matter if tripod or not. I am starting to be annoyed by IBIS system.
For references, take a look at these reviews regarding field curvature.
And I am also starting to feel that the 14-24 DG DN test at Lenstip is not very realistic as almost all of the sample photographs are not properly focused, since corners are soft in everyone, no matter the f-stop number.
I also feel the same for other test at Les Numeriques where the reviewers where unable to properly focus at close distance the Sigma 14-24 DG DN. Consequently the results are very soft at f2,8-f4, where the field curvature shows its maximum effects. They even explained that the Imatest numbers for sharpness were much higher than what the photography test suggest. This may lead to mistakenly conclude that the 14-24 is soft wide open, which is not true in my experience.
p.44 #5 · Sigma 14-24mm f/2.8 DG DN first impressions
JeyB, couldn't the greater width of the rear axle (distance protruding from the handle outwards towards the camera) be the cause of that misfocus in that particular scenario? If it was, you could use Mark's recommendation for Hyperfocal and shift the focus point closer to camera (maybe center point of the widebody rear fender would have yielded both in acceptable critical).
p.44 #6 · Sigma 14-24mm f/2.8 DG DN first impressions
JeyB wrote:
Hi
I've been testing furtherly my 14-24 DG DN. In my opinion it has noticeable field curvature issues which need to be understood in order to obtain the maximum potential of the lens for corners sharpness.
What I've been testing is different focusing points to maximize corner acuteness. When I focus on dead center, no matter if close or at infinity, corners are not going to be maximally sharp. Only if I select a point of focus toward middle of the right side then the corners are brilliantly acute. Of course that when practicing this focus method then the center is less sharp than when focus point is selected at the center of the frame. But this is a compromise we have to accept to have corners at high level.
Another method is to focus on the center part of the frame and then zoom in with the focus magnifier assistant to check the corners. If they are soft proceed to manually tweak the focus ring slightly and improve them to get tack sharp acuteness and then shoot. When doing this, the center probably will lose some sharpness, but not very much in my view.
When using the Sigma 14-24 DG DN I have decided to disengage IBIS permanently in the camera body to avoid weird issues of drops in sharpness along random parts of the frame. Always off, no matter if tripod or not. I am starting to be annoyed by IBIS system.
For references, take a look at these reviews regarding field curvature.
And I am also starting to feel that the 14-24 DG DN test at Lenstip is not very realistic as almost all of the sample photographs are not properly focused, since corners are soft in everyone, no matter the f-stop number.
I also feel the same for other test at Les Numeriques where the reviewers where unable to properly focus at close distance the Sigma 14-24 DG DN. Consequently the results are very soft at f2,8-f4, where the field curvature shows its maximum effects. They even explained that the Imatest numbers for sharpness were much higher than what the photography test suggest. This may lead to mistakenly conclude that the 14-24 is soft wide open, which is not true in my experience.
Is your copy well centered across the whole range? The various copies I have tried indicate to me that fleld curvature is very low for such a wide lens, but sample variation is such that FC can look like it is stronger on some copies. Also, unless the reviews you mention use flat surfaces or infinity-only scenes, they will not be much use in assessing FC.
p.44 #7 · Sigma 14-24mm f/2.8 DG DN first impressions
ftllens wrote:
JeyB, couldn't the greater width of the rear axle (distance protruding from the handle outwards towards the camera) be the cause of that misfocus in that particular scenario? If it was, you could use Mark's recommendation for Hyperfocal and shift the focus point closer to camera (maybe center point of the widebody rear fender would have yielded both in acceptable critical).
Well, I think it is not the case, bear in mind that it was shot at f7,1, enough to big depth of field. Aside that, what I see the softer is the inner part of the wheel, the Porsche logo and the text inscriptions near the RS word and even the Michelin words and logo. Both wheels, front and rear, are approximately in the same plane. I don't appreciate softness in the metal bodywork of the car. The outlines are well defined in the vicinity of the rear wheel. I think that the issue is more related to IBIS than to field curvature. I still have to take another test shots to double check.
p.44 #8 · Sigma 14-24mm f/2.8 DG DN first impressions
rvh23 wrote:
Is your copy well centered across the whole range? The various copies I have tried indicate to me that fleld curvature is very low for such a wide lens, but sample variation is such that FC can look like it is stronger on some copies. Also, unless the reviews you mention use flat surfaces or infinity-only scenes, they will not be much use in assessing FC.
Hi rvh23
I think it is quite well centered. Fred checked out my test shots some time ago, which I am also posting here again. He told me it was a fine unit, slightly decentered at 24 mm but he also commented that it is imposible to get a 100% perfect zoom, which I agree totally.
It is interesting what you point out about FC not being able to show on a flat surface. From my experience it is indeed posible. Keep in mind that what is causing the FC is the rounded external element of the lens and that the plane of focus shifts wavyly along the entire flat sensor plane. What I didn't know is that some copies of a FC'd lens may have more FC than other copies.
In the test of Les Numeriques it is easy to see that they were not able to properly focus for simultaneously sharp center and corners at the same time. It may also be possible that the copy they had were more prone to a high FC degree. By the way, the averaging of 10 copies that Roger Cicala applies to all his tested lens is really a good idea that gives much more credibility to the tests he publishes.
What I am considering is to sell my copy and to get an Sony 12-24 f4 G, which has been tested at Lensrentals and its field of focus is very flat with almost no FC at all. I am somewhat confused now, but I have to experiment more with my Sigma lens before doing that.
Here are the test shots for decentering of my unit:
p.44 #9 · Sigma 14-24mm f/2.8 DG DN first impressions
I've tested several samples of the Sony 12-24 in the past. And none of these samples were in the corners as sharp as the Sigma. I would not recommend to exchange the Sigma against the Sony.
My Copy of the Sigma is (for an ultra-wide angle lens) rather flat field at infinity. But I haven't yet tested for FC at closer distances. That FC behavior changes with focus distance is not uncommon (the Zeiss 15mm is for example a lens were FC changes a lot over focus distance).
p.44 #10 · Sigma 14-24mm f/2.8 DG DN first impressions
It's rare for a ultra wide angle lens to have negligible field curvature. (Only the FE 24/1.4 GM and Batis 25/2 are pretty much flat field)
I find the Sigma 14-24/2.8's FC very minimal across the range (Not as noticeable as Lox 21/2.8 and CV 21/1.4 for instance)
p.44 #11 · Sigma 14-24mm f/2.8 DG DN first impressions
Bobu wrote:
I've tested several samples of the Sony 12-24 in the past. And none of these samples were in the corners as sharp as the Sigma. I would not recommend to exchange the Sigma against the Sony.
My Copy of the Sigma is (for an ultra-wide angle lens) rather flat field at infinity. But I haven't yet tested for FC at closer distances. That FC behavior changes with focus distance is not uncommon (the Zeiss 15mm is for example a lens were FC changes a lot over focus distance).
Ok. I'll take your words for granted. And I will have to perform more tests in different conditions.
What a complicated thing is UWA!! I suppose the designers have to face off some compromises when developing this kind of lenses... even more in a zoom design.
The more I am learning about lenses idiosincracies the more I admire those photographers that master the landscape art.
p.44 #12 · Sigma 14-24mm f/2.8 DG DN first impressions
Fred Miranda wrote:
It's rare for a ultra wide angle lens to have negligible field curvature. (Only the FE 24/1.4 GM and Batis 25/2 are pretty much flat field)
I find the Sigma 14-24/2.8's FC very minimal across the range (Not as noticeable as Lox 21/2.8 and CV 21/1.4 for instance)
So you have in high regard the Sigma14-24 f2,8 DG DN, isn't it?
Now off topic, I am lately guiding myself by this forum to select excellent and contrasted equipment. There are tons of deep and reliable information. Although I am still a newby 'round here, I enjoy a lot to read some illustrated contributors' commentaries and learn from them. It is really the only site that inspires my confidence.
And I am also hooked at the 600 mm GM photo thread. Gorgeus photographs there.
Nice place to land this FM forum. Full of respect.
p.44 #13 · Sigma 14-24mm f/2.8 DG DN first impressions
Got a shipping confirmation for my 14-24mm DG DN, hope it arives soon. Hope it doenst have astigmatism blobs at f8 (my biggest worry), that usually points to not perfect copy.
p.44 #14 · Sigma 14-24mm f/2.8 DG DN first impressions
Matti6950 wrote:
Got a shipping confirmation for my 14-24mm DG DN, hope it arives soon. Hope it doenst have astigmatism blobs at f8 (my biggest worry), that usually points to not perfect copy.
p.44 #15 · Sigma 14-24mm f/2.8 DG DN first impressions
JeyB wrote:
Hi rvh23
I think it is quite well centered. Fred checked out my test shots some time ago, which I am also posting here again. He told me it was a fine unit, slightly decentered at 24 mm but he also commented that it is imposible to get a 100% perfect zoom, which I agree totally.
It is interesting what you point out about FC not being able to show on a flat surface. From my experience it is indeed posible. Keep in mind that what is causing the FC is the rounded external element of the lens and that the plane of focus shifts wavyly along the entire flat sensor plane. What I didn't know is that some copies of a FC'd lens may have more FC than other copies.
In the test of Les Numeriques it is easy to see that they were not able to properly focus for simultaneously sharp center and corners at the same time. It may also be possible that the copy they had were more prone to a high FC degree. By the way, the averaging of 10 copies that Roger Cicala applies to all his tested lens is really a good idea that gives much more credibility to the tests he publishes.
What I am considering is to sell my copy and to get an Sony 12-24 f4 G, which has been tested at Lensrentals and its field of focus is very flat with almost no FC at all. I am somewhat confused now, but I have to experiment more with my Sigma lens before doing that.
Here are the test shots for decentering of my unit:
Agreed, your copy looks fine. It looks close to perfect at 14mm, and only slighlty asymmetrical a the long end. Given we are talking about wide open performance, that's rather impressive for a zoom. By F5.6 it should be great across the whole range (and noticeably better than a Sony 12-24 in the corners).
My previous comment about FC assessment methods was in relation to those lens reviews that use general 3D scenes to assess corner sharpness. If you don't have everything in the scene at the same distance from the camera (e.g. a flat surface, or everything at infinity) the assessment of FC will clearly be compromised by DOF considerations.
p.44 #16 · Sigma 14-24mm f/2.8 DG DN first impressions
Fred Miranda wrote:
As long as the thickness is around 0.1-0.2mm (gel or film filters), field curvature remains unaffected even at the wide range wide open.
0.3mm is pushing the limits but works quite well when I tested the Aurora 0.3mm rear NDs. Anything thicker than that will cause adverse effects on field curvature.
So far we have the following rear ND filter options for the Sigma 14-24 E-mount:
p.44 #18 · Sigma 14-24mm f/2.8 DG DN first impressions
Shit, it can't be mounted at all. The nose on the filter is too thick for the slit on the lens. The design of the Kase is different to the Haida. I will post some pictures soon.
The Kase filter is on the left, the Haida on the right. The small lower nose is too thick for the slit on the lens. The Haida doesn't have this nose.
Sadly the Haida is 0.5mm thick, otherwise it would be perfect.
The Kase filter is on the left, the Haida on the right. The small lower nose is too thick for the slit on the lens. The Haida doesn't have this nose.
Sadly the Haida is 0.5mm thick, otherwise it would be perfect.
thats a bummer. It looks like the nose is suppose to tuck under as seen here.
