Monday, December 4, 2017

Two cameras, three lenses, one rose bush, part 1

Fair warning. This post will be boring for the non-photographers of you. Even some photographers might be bored. I was doing some experiments to understand my new camera better, and what better way to do that than compare it to the old camera?

The intent is to compare a Canon T6i to a Canon 6D Mkii, using three different lenses. The lenses are the Canon 100 mm f2.8L IS macro used as a reference, the Tamron 70-200 mm f2.8, and the Canon 24-70 mm f4L IS.

All shots were done at ISO 100 in bright sunlight at f4. The cameras were on a tripod aimed at a particular rose bush in our front garden. For each camera I shot the 100 mm lens first to get a grip on what it 'saw' and tried to ensure the other lenses were set to 'see' the same field of view on each camera. I realized only in the middle of the shots that the tripod shoe on the 70-200 mm lens is ever so slightly not lined up with the lens, so I ended up having to move the tripod head slightly between shots.

I shot them in the order of 100 mm, then 70-200, then 24-70 on the 6D, then the T6. I let the autofocus do it's thing. That was a mistake. Once I drill in a bit, I can see the focus point moved around a bit which makes it a bit harder to compare apples to apples. Rather than the rose bush, I should have put the centre point on the corner of the flowerbed.

For people not familiar with the camera model numbers, the 6D MKii is a full frame sensor that is 35.9 x 24 mm and produces an image 6240 x 4160 pixels, and the T6i is a APS-C or 'crop' sensor that is 22.3 x 14.9 mm and produces an image 6000 x 4000 pixels.

There is zero processing in Lightroom, so they will look a little flat and lifeless. The photos were imported from different chips, and exported in one batch, using my usual social media settings.

100 mm macro lens, first the 6D, then the T6.



70 -200, first the 6D, then T6.



24-105, first the 6D, then the T6i


You will have noticed that even though all the lens were shot as close to 100 mm as I could get, the photos look very different from camera to camera. The T6 images are a narrower field of view, so the rose bush appears larger. The photographers reading this know the multiplication factor is 1.6. If anyone wants me to explain why the factor is 1.6, you have to buy me a beer, and I'll explain. Just to warn you, there are optical physics involved.

While I was at it, I compared the two cameras with the same Canon lens at 24 mm, first the 6D then the T6.



 Then I compared the Tamron lens at 200 mm, first the 6D, then the T6.



Lastly I did some more playing with the Tokina 11-20 mm f2.8 on the 6d. In the Canon world, a lens that fits on a full frame DSLR will also fit on a crop sensor, but the crop sensor cannot take full advantage of the lens. If you try to put a crop sensor lens on a full frame camera, you will get a black ring around the image because the lens sends a ray of light that is narrower than the sensor. My Tokina lens is a little odd in that I get the black ring when the lens is at the widest, but not at the narrowest, so I thought I'd document this.

This is the 6D at 11 mm (the widest this lens will go.) All these are still at ISO 100 and f4, aimed at the same rose bush. Don't worry about the weird looking shadow lines around me and the tripod, they're from a tree across the road.


14 mm

16 mm

18 mm

20 mm

I normally think of this lens as my astro lens. It can see lots of the sky and it's a fast lens. Note to self when shooting this on the 6D, set it at 18 mm.

Conclusions.
The different crop factor makes it tougher to directly compare than I thought. While I tried to get the exposures the same, its possible the 6D was reading a hair darker than the T6. Or it's picking up slightly richer colours from what is a pretty desaturated scene. 

All the photos are pretty good, as you'd expect for good quality lenses. I did some pixel peeping in Lightroom to look at the details, such as the red rose hip, or some of the individual thorns. That's where I learned the autofocus picked slightly different points. That makes it impossible to compare how well the sensors pick up details. If I want to compare the image quality, I need to be much more careful shooting the images. 

Learnings
Comparisons can be tricky things, and I didn't think this one through as well as I should have. Force the camera to focus using the center point on a fixed spot, like the corner of the flower bed. Double check exposure settings. Maybe put some text from a book, or a page from a magazine in the photo, along with some natural scenery. I could even close down the aperture to f10 or f15 and see how that affects the images, which implies some parts of the scene are much closer to the camera than other parts.

I suppose I should do a more complicated comparison, where I set the 24-105 lens to 24 mm on the T6, and about 38 on the 6D, and then about 35 and 50 respectively, and about 65 and 105 respectively. The attentive of my readers will notice that 1.6 factor again. 

The other thing to try is to shoot each camera with the 100 mm lens so I don't have to worry about zoom issue, then digitally crop the 6D photo so the field of view is the same, then compare the images.

Both of these are a lot of work, and I really should pick a scene that gives more of a challenge to the cameras. Perhaps the garden in full bloom, or a forest river landscape down in Fish Creek. I confidently predict that none of my photo buddies will want to join me in doing this, where they might be interested in a photo ramble.

Comments
There is more to photography than the photographic end result. There's the experience of actually shooting, and the 6D is a better camera for that, by far. It fits my hand better, has a bigger viewfinder with more information that makes composition easier, and I am getting a technically better image quality if I can improve my technique to take full advantage of it.

If I want to shoot birds or distant wildlife, I'm more likely to take the T6i and the 200 mm lens to get as much reach as possible. For most other things, I'm going to take the 6D to get the better sensor and full advantage of my lenses. I haven't compared macro photos yet, maybe I'll do that for the next macro Monday.

Here's a photo of the two cameras. Note the 6D has a quick release plate on the base, so it is sitting about a cm higher. Otherwise the two cameras are a similar size, with the 6D being a bit bigger. The T6 has a 17-50 lens that was not part of the comparison.


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