Oversampling 5.1K to 4K is apparently less taxing on the camera than 8K to 4K, so the R5 does not heat up or require periodic cool downs as it does when shooting “4K HQ” video. The only limitation with “4K Crop” then is the R5’s 30 minute record time limit, which is standard in all their non-cinema cameras. Downsides of the Sigma 18-35mm f/1.8 Comparing the 18-35mm on a mid-range APS-C body to the Tamron 24-70mm F2.8 on one of the latest, similarly enthusiast-focused full frame DSLRs, there's essentially no difference in overall bulk. The small differences in weight and and length between the lenses make no appreciable difference to the handling, either. The main difference lies in the 18-35mm's internal zoom design, whereas most 24-70mm F2.8s extend substantially on zooming. Autofocus The lens seemed to do best within about 8 feet, but in the crucial portrait window of 8-15 feet (for full body shots) the focus accuracy dropped dramatically. This reveals one of the problems I (and others) have experienced with the lens. You can set an effective microadjustment value for a certain distance, but that value may not be the right one for other distances. Overall though, this level of chromatic aberration is impressively low, especially considering that we're looking at an ultra-fast zoom. It's no worse than we'd expect to see from fast primes, either. Flare

Sigma 18-35mm f/1.8 DC HSM ART Review - DustinAbbott.net Sigma 18-35mm f/1.8 DC HSM ART Review - DustinAbbott.net

These lenses can be compared in several different ways, but its clear that regardless of whether we look at them them both tested on the same camera body, or at how the Sigma on APS-C compares to the Tamron on full frame, the 18-35mm easily holds its own in these studio tests. Compared to Canon EF-S 17-55mm f/2.8 IS USM Most people changing formats from APS-C to full-frame are likely to find themselves buying 24- or 28-70mm F2.8 zooms, as such a lens makes it easy to access the larger format's low-light and shallow depth-of-field capabilities. The key to understanding the Sigma 18-35mm F1.8 is to realize that it gives the same control over depth-of-field as a 28-50mm F2.8 would on a full-frame camera - it also allows you to shoot at wider apertures in any given situation, effectively cancelling out the greater low-light ability that a larger sensor would otherwise give. And, especially if you own a high-end APS-C camera, that can help to reduce some of the motivation for moving to full-frame.Sigma's choice of F1.8 as maximum aperture isn't a coincidence; it means that the lens will offer the same control over depth of field as an F2.8 zoom does on full frame. What's more, combined with an APS-C sensor, the system will also offer effectively the same light-gathering capability as an F2.8 lens on full frame. By this we mean that it will be able to project an image that's just over twice as bright onto a sensor that's slightly less than half the area, meaning the same total amount of light is used to capture the image. This is important as it's a major determinant of image quality. Essentially it means that APS-C shooters will be able to use lower ISOs when shooting wide open in low light and get similar levels of image noise, substantially negating one of the key advantages of switching to full frame. But because the R5 can shoot 8K video, Movie Cropping applies a 1.6x crop to an 8K image. This creates a 5.1K image, which is then downsampled to 4K. This is what Canon calls “4K Crop” video.

Used Sigma 18-35mm f/1.8 DC HSM ART - Canon EF-S Fit - MPB

This procedure certainly improved overall focus accuracy when shooting at the distances used for microadjustment. However these are fixed by the software, and there's no option to specifically correct any distance between infinity and 0.5m. Unfortunately though, the vast majority of subjects end up somewhere in between, and we found that the lens still had some problems with focus accuracy even when fully programmed as above. Knowing this, we'd probably configure the 'Infinity' position with a bias towards getting the most accurate focus at closer subject distances. Crop” video is higher quality than regular 4K, which is what you get when 4K HQ mode and Movie Cropping are both set to “Disable” (see below). 4K HQ mode disabled on the Canon EOS R5 At night, the lens is a bit less accurate, but it correctly focused (in nearly pure darkness) ten out of thirteen times. In a couple cases, it was just a little slow in finding a subject, by which I mean it took it about one and a half seconds instead of half a second. The performance is on par with what I have found with most good quality lenses on the market, third party or otherwise. No lens is going to hit every time in exigent circumstances, so I’m pretty satisfied with how the Sigma did here. Every time I review a Sigma lens I will be closely looking at the AF (autofocus) performance. I’ve rarely had a problem with HSM motors when it comes to sound or speed (they are amongst the quietest focusing lenses that I’ve encountered and generally quite fast), but I have major concerns when it comes to AF accuracy and consistency. The Sigma 150-600mm Sport was the first Sigma lens that I walked away completely satisfied from when it came to its AF performance. I’m afraid the 18-35mm ART didn’t impress out of the box. My review body is a Canon EOS 70D, and trying to use my typical AFMA program ( Reikan FoCal) produced such variation that an automatic calibration simply didn’t work (the program gave up). I did a semi-automatic calibration using my own eyes, and discovered why. Just when I thought I had a value zeroed in, the results would jump around. The focus peak looked like a yo-yo. I’ve never had such a difficult time calibrating a lens before.The Canon EOS R5 is, however, smarter than the 5D. The R5 recognizes the Sigma 18-35mm’s crop factor and automatically changes its Cropping/Aspect Ratio setting to “1.6x (crop)”. APS-C lenses automatically enable “1.6x (crop)”. All other options disabled.

Sigma 18-35mm F1.8 DC HSM A Canon mount lens review: fixed Sigma 18-35mm F1.8 DC HSM A Canon mount lens review: fixed

As I said earlier, there are two ways to look at this lens. Before examining those, however, let me first say that this is undoubtedly one of the finest crop specific lenses out there. APS-C has received relatively little development dollars from most manufacturers and as a result APS-C lenses tend to be budget options with variable apertures. This lens is as lovingly designed as other Sigma ART series lenses, and thus it is the Cadillac of crop sensor zooms. I’m happy that such a lens exists. It does indeed exist…should you buy it? There's a comment in the introduction part of this review that doesn't make sense to me. I think it's wrong, but perhaps I'm missing something. Dpreview states, "it will also offer effectively the same light-gathering capability as an F2.8 lens on full frame", "meaning the same total amount of light is used to capture the image", "APS-C shooters will be able to use lower ISOs... substantially negating one of the key advantages of switching to full frame." To find the full-frame, “35mm equivalency” of the APS-C Sigma 18-35mm, you multiply its focal length by crop factor (which is 1.6 for Canon cameras). This translates to an effective 27-53mm focal length range on full-frame cameras. The net result is an optically-zoomed, clean image without any vignette (see below). Sigma 18-35mm f/1.8 on the Canon EOS R5 (1.6x Crop Aspect Ratio) This is pretty hard to accept when I am accustomed to coming home from a wedding with 700-1000 shots taken with my own kit and typically won’t have to discard one shot for missed focus. Some report that their copy of the lens consistently focuses accurately, but others report similar frustrations with inconsistent focus results. Put simply, I think there is copy variation, and the fact that I reviewed a new retail copy some 2 years after the release date of the lens tells me that Sigma hasn’t been able to completely nail down this issue.

You can also find this on Lensora.com

The pictures below illustrate the focal length range from wide to telephoto (on Canon APS-C, 1.6x). The 18-35mm covers a modest 2x zoom range. This lens isn’t specifically built for macro, with maximum magnification of 0.23x and a minimum close-focusing distance of around 11 inches. While on that note, the lens is rather large, especially for what many of you will be used to with this focal range. It’s a few inches longer than a comparable Canon 18-55mm or Nikon 18-35mm. The entire zoom range is internal, so it doesn’t change sizes on you. I had a weird issue with my lens and Sigma says that they haven’t seen this before: while in auto-focus, my camera did not beep to alert me that an image was in focus. As soon as I switched to manual focus, the camera beeped as usual. It only affected the lens while in auto-focus mode. I know many people turn the beep off to begin with, so it’s not going to be a big deal to them. The viewfinder still flashed red when an image was in focus, I just got no auditory alert.