Sony A7R vs Sigma DP3Merrill

Started Feb 11, 2014 | Discussions thread
blue_skies Forum Pro • Posts: 11,470
Re: Sony A7R vs Sigma DP3Merrill

OvinceZ wrote:

I posted this on the Sigma forum but want to get a reaction from Sony owners.

One of the things about photography and the internet is that we get caught up in all the new offerings and feel compelled to buy the latest and greatest. I recently got the A7R and was keen to try it out in Sydney where it is summer. Last Friday I walked across the Anzac Bridge and brought my tripod with me to make sure the photos were as sharp as possible. I used the DP3M a lot, too, because I knew I would get plenty of detail in photos.

I took many shots from the same location using both cameras. I could have used my 70-200F4is lens to have a similar focal length to the 75mm equivalent Sigma lens. However, I wasn't doing a comparison and besides, I dislike changing lenses too often. I used the 35mm FE lens and also my 50mm Canon macro lens with the Metabones adapter. When I viewed the photos on my 30 inch monitor I was surprised at how awful the cables looked in all photos but the Sigma produced them clearer. The distant buildings were clearer on the Sigma. Makes me wonder why I got the A7R.

Looking at them in detail, it appears to be a struggle between heat simmering and the JPG engine. The JPG engine may be struggling with angled lines and it makes me wonder if you were using X.Fine and NR off/low. But the buildings in the back look virtually similar on both images, when sized to similar sizes. Whether that is my monitor doing this is not clear, but it feels as if I am hitting the resolution of the image. That is, the window lines are jagged - on both images - and you would expect them to be straight. Perphaps an artifact of the hot weather.

Other than that, tripod & base ISO, the only difference is using f/8 for 50mm on APS-C (f/12 and 75mm on FF) versus f/8 and 35mm and 50mm on FF.

You inadvertently have 'zoomed-in' the Sigma image by the crop ratio, while giving it extra DOF.

That is, from the same standpoint, the 15Mp Sigma image is from a 75mm FF equiv image. If you crop the A7r image to a 75mm view, you have to crop 1.5x or 2x depending on whether you use the 50mm or 35mm image. At 1.5x, you loose half the pixels, becoming more or less equivalent with the Sigma, and at 2x you have fewer pixels for the cables in the A7r image than in the Sigma image. Either way, the A7r has no advantage in resolution over the Sigma for the cables in the image.

To do a fair comparison, use a 75mm lens on the A7r, if shooting from the same standpoint.

I think that essentially you have only noticed the differences between a 35mm, 50mm and 75mm, and noted that the 75mm resolves the most detail.

Why the details is not as sharp as it should be, again, could be because you are close to the resolution limit, because the angled lines don't map well through the JPG engine, or because of the radiant heat that makes the air simmer.

I wouldn't think too much of it, imho.

However, I am pleased with it for most occasions. The cables on this bridge are a challenge for any lens and camera. It was also quite warm in the afternoon so there could be some atmospheric distortion caused by the warm, black cable coverings. The fence beside the footpath is also lacking much detail but looks better in the Sigma photo. The fence is a wire mesh having rectangular holes about 1 inch X 2 1/2 inches. No way you can get a lens through those gaps. Curses on the engineers who replaced the original fence. I guess security is everything nowadays. They could have put small holes along the fence so you could put your lens though it. The views from up there are beautiful. I had to use my tripod and 10 second timer and hoisted the camera above the 9 foot high fence. Took a few goes to get the right framing. The shutter is so loud and pronounced on the A7R that I always knew when the shutter was activated! I could feel the vibrations.

Have a look and see for yourself. No editing whatever in any of the photos. Straight out of the camera jpgs from the Sony. The Sigma files were put through the process to get a tiff file then saved in Photoshop as a jpg. Reduced the size to make them manageable here.


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