Sigma 24-70 EX DG là một len rất tốt, giá rẻ so với các đối thủ cùng tầm. Bài kiểm nghiệm so sánh của bác up209d cung cấp. Nhận xét : Sigma 24-70 EX DG là một len rất tốt , AF rất nhanh , nhanh hơn Tamron 28-75 thấy rõ và cũng kêu to hơn thấy rõ nữa , Sigma 24-70 đời nào gắn chip AF tốt thì sẽ cho focus cực tốt , thông thường thì khoảng 5 - 6 con có lẽ mới đc một con gắn chip chuẩn. Build hoành tráng chắc nịch ko kém gì Canon 24-70 thiếu khện mỗi cái viền đỏ, lớp nhung cầm rất đã tay , nhung con này rất tốt em sử dụng một thời gian dài mà chưa thấy bị bong tróc gì , thi thoảng bẩn quá nó trắng trắng thì lau đi là lại mới kính cong. Nhưng nói chung ko có lớp nhung thì vẫn tốt hơn =]]
Về chất ảnh , độ chi tiết cao sóng sánh vs các loại len cùng giải tiêu cự. Thua chi tiết hơn Tamron 28-75 ở rìa ảnh chút , nhưng ko bị ám vàng , mầu sắc gần bằng Canon. Sigma 24-70 đúng là bị Flare khá rõ, có hood vào thì cũng cải thiện đc hơn chút. Về hiện tượng Flare và Halo của Sigma, do cái Hood quá bé ko làm tròn đc hết nhiệm vụ nên nhiều khi phải sử dụng chính 1 tay che phần ánh sáng xiên, đảm bảo kết quả hơn cả mong đợi, thậm chí còn cho ảnh tương phản hơn cả Ca 24-70L
Về giá thành , là một len giá thành rẻ chất lượng ko đồng đều , nếu chọn đc một em nét cực đại thì chắc là cũng ko ngán đối thủ nào.
Sigma 24-70 @50mm F2.8 1/250s ISO 400
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Sigma Vs Canon : @70mm F2.8
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Canon
Center Crop 100%
Nhận xét : Mầu Canon ấm hơn , Sigma cho nét tâm có vẻ là nhỉnh hơn , Canon ít bị Flare hơn.
Sigma Vs Tamron 28-75
Sigma
Tamron
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Edge
Nhận xét : Nét tâm Sigma chi tiết hơn , nhưng nét viền Tamron tốt hơn hẳn , Tamron có bị hiện tượng Ghost ở mở khẩu , bị ám vàng tuy nhiên Flare kiểm soát tốt hơn Sigma. Hiện tượng Ghost ở Tamron 28-75 là rất phổ biến, em nghĩ có thể do cách đặt thấu kính có vấn đề, đây là ống tamron em thấy ít bị ghost nhất , và cũng là ống nét nhất em từng gặp. Ai có ống nét hơn thì thông báo cho em, anh em ta cafe làm bữa test luôn.
Test nữa...
Sigma 24-70 vs Canon 85 @F2.8
Canon
Sigma
Center Vs
Nhận xét : Zoom thì chẳng thể đọ vs Fix , nhưng xét ra độ nét của Sigma ở mở khẩu hết cỡ cũng rất đáng kể.
Sigma 24-70 EX DG vs Tokina 28-70 ATX PRO [Thank đồng chí Naul đã dũng cảm thẩm du em Tokina để anh em có điều kiện được test]
Về Build , Sigma phi 82 trong khi Tokina phi 77, Build của Tokina rất chắc chắn và toàn bộ bằng kim loại nên khá nặng và đầm tay, mặc dù ngoại hình bé hơn nhưng vs lí do trên mà trọng lượng của Tokina có thể ngang vs Ca 24-70L. Vòng MF hơi khó dùng và cũng mất hai thao tác như Sigma
Về mầu sắc Tokina thiên về lạnh, Sigma cho mầu sắc ấm hơn
Sigma cho ảnh đậm đà và lập thể hơn Sigma trên - Tokina dưới
Về độ nét , ở tâm cả hai ngang nhau , về viền Tokina bị viền tím.
Về AF , cả hai đều rất nhanh, nhanh và chuẩn hơn AF của Tamron rõ rệt, Tokina AF êm hơn trong khi đó Sigma thì khá ồn ào.
Về giá thành , Tokina rẻ hơn Sigma [4 tr vs 5 tr] , là một len rất xứng đáng vs giá tiền nhưng khá hiếm.
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The Nikon 24-70mm lens is one that has been praised by every photographer who picks it up. The only issues that some people find with the lens is that it is heavy, large, and expensive at around $1,700. That price tag makes it hard for hobbyist photographers to justify purchasing a lens that costs more than most camera bodies. That is where third party companies like Sigma and Tamron come in to make lenses more affordable to photographers. Sigma had previously released a 24-70mm lens, but it lacked a focusing motor. The new Sigma 24-70mm f2.8 DG HSM adds a focusing motor and a smaller size.
For those of you who like to read the tech specs, look below. If you don’t like reading tech specs scroll further down for my review and sample images.
Technical Specs
Lens Construction 14 Elements in 12 Groups Angle of View 84.1-34.3 # of Diaphragm Blades 9 Minimum Aperture f22 Minimum Focusing Distance 38 cm / 15 in Filter Size [mm] 82mm Maximum Magnifications 1:5:3 Minimum Focusing Distance 38 cm / 15 in Dimensions 86.6mm mm/3.5 in Weight 790g / 27.9oz.
Lens Construction
Here is what all the letters on the lens mean:
HSM – Hyper-Sonic Motor
IF – Inner Focus
EX – EX Lens
DG – DG for Digital
ASP – Aspherical
G – G type Nikon mount lens
Overall Impression
When I first received the Sigma 24-70 I was surprised at how small the lens was compared to the Nikon version. By smaller I mean it is shorter, but when you look at the lens you notice that it is wider than the Nikon. I liked the fact that it was shorter because it would be easier to take around with me. I really don’t like walking around Austin with the big 24-70mm, and its huge lens hood. It’s really bright here so I always like leaving the lens hoods attached. So not only did I have a lens that had a fast aperture, but it was also small enough that it was comfortable to carry.
Something else to note is that the Sigma lens has a satin/silky finish to it as well as the lens hood. That was a first for me. Normally I’m used to feeling either hard plastic or metal when touching lenses. I’m not sure what the lens is coated/covered with but it feels nice. I did notice that on a friend’s Sigma 70-200mm OSM that the lens doesn’t have the same finish. We’ll have to see if Sigma’s next iteration of the 24-70mm shares the satin finish.
The only other thing to mention is that the lens zooms clockwise, opposite to what you are used to on Nikon lenses. This didn’t really bother me while I walked around taking sample shots. I have shot with Canon lenses before so that might be why I’m used to zooming both ways.
Build Quality
The lens itself feels heavy and well built. I personally preferred the Sigma’s build quality over that of Nikon’s 18-105mm or 28-300mm lenses. The focus and zoom rings are made of plastic, but it does feel better than other lenses I’ve used like Canon’s 50mm f1.4. The lens hood is plastic and is smaller than the Nikon version. The hood slides on nicely and clicks when it is on correctly. I was really impressed overall with the build quality. When I shot some of the sample images, I was walking around in 105 degree weather for an hour and a half with no issues. The lens held its own even in the extreme heat.
As you can see in the image below the lens mount is metal. The only thing that the mount is missing is the rubber gasket present on Nikon pro lenses. That helps to ensure that water doesn’t get into the camera.
The only issue I had with the build quality of the lens was the auto/manual focus switch on the side of the lens. The switch does not match the finish of the lens, and protrudes from the barrel of the lens. It would occasionally switch from Autofocus to Manual focus from rubbing against my body while being carried on a BlackRapid strap. It just seems like the switch was an afterthought rather than being designed into the lens.
Focusing
I walked around and shot with the Sigma 24-70mm, and would then switch the Nikon 24-70mm in order to compare focusing speeds. I found that the Nikon focused just a bit quicker, and was more reliable. The Sigma would sometimes have to go through the full focus range before catching focus. But for being about $900 cheaper than the Nikon it performed exceptionally well. The addition of the HSM motor is what helps this lens focus fast and accurate while still being silent.
Image Quality
I was really surprised when I got back home and opened Aperture to look at the photos shot with the Sigma 24-70. The images produced were sharp and the contrast was great. In Aperture I took out the Loupe [100% magnification] and I was surprised to see how sharp the images came out. Even in the corners of the image I lines were still sharp.
There was slight signs of purple fringing when I examined some tree leaves in the corner of some images. But other than that the Sigma 24-70 delivered on the most important piece, image quality. The images shown in this section have not had any sharpening done in Photoshop.
In the picture below you can see how a f2.8 aperture allows you to separate your subject from the background.
As you can see in the image below I was able to get some flare to show up when pointing the lens towards the sun. It wasn’t terribly bad considering the sun was right above the building I was shooting.
Conclusions
After getting to use the Sigma 24-70mm 2.8 DG HSM I would have to say that it is a great buy for anyone that isn’t looking to spend $1,700 on the Nikon version. For the $900 spent on the Sigma 24-70 you are getting a lens that delivers quality images at almost half the cost of Nikon’s 24-70mm lens. That $900 savings allows you to purchase maybe a 50mm 1.8 prime lens, and other accessories.
I think overall that the Sigma 24-70mm lens is a great alternative to the expensive Nikon version. As long as you don’t mind buying a third party lens you will be happy with the images that this lens captures. I was really surprised to see how well this lens did considering I own the Nikon 24-70mm lens.
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