CHG_CANON Loc: the Windy City

Now Bob, you said there was no budget limit, so I felt free to spend your money was if it was my own. A very common impulse here on UHH.

But, if we should be spending wisely rather than without limit, you should step away from the shopping sites and make more informed decisions. You own an industry standard 24MP DSLR. In your EF-s 10-18 IS, you have one of the greatest wide angle lenses ever created. A full-frame camera and a bag full of L-lenses will do little to make you a better photographer, rather, just a photographer with more expensive equipment. The image result differences between your EOS T6i and any new camera, other than a mirrorless with native mirrorless lenses, will be rather marginal and subtle to detect.

As I regularly ask of others: Do you shoot in RAW? Do you use commercial-grade editing software? Do you own a tripod? An external flash? Have you really reached the limits of your current gear? Have you posted any example images and asked for feedback on your work and ideas to consider? Where / how do you use your digital images? Do you have a realistic and effective back-up strategy for your images and computer hardware in general?

Any of your 'no' responses to the questions above should be addressed prior to a large investment in new camera equipment.

Changing your question from before based on keeping the Rebel and preparing for a slower, long-term plan, consider instead:

Sell the EF 75-300, EF-s 55-250, EF-s 18-55

Buy the EF-s 18-135mm f/3.5-5.6 IS USM

If you don't have a quality tripod, spend the $300 to $800 needed for a quality model, along with a top ball-head, a quick release clamp and an L-plate for your Rebel. Look online such as eBay for quality tripod models.

When you need a longer / new lens, look only at full-frame EF models that fit / fill some need. If your interests need something 'longer', consider the EF 70-300mm f/4-5.6 IS II USM. If you aspire to wildlife rather than general uses, consider the 100-400L II discussed earlier rather than shorter zooms.

/paul

John N Loc: HP14 3QF Stokenchurch, UK

I have recently bought the 6DmkII and am quite pleased with it. The stock zoom that comes with it seems to be better than the 15-85 I have with my 60D.

Forget the money issue. The 6D is a bit lighter and smaller than the 5D and for some this is a significant benefit. The weight saved may also allow use of the 'L' series zoom. Unless you've got a specific need for something only the 5D can do I'd go for the lighter 6D. Or go to the gym.

leftj Loc: Texas

Between these two cameras, if money is no object then the 5D IV is a no-brainer.

ltj123 Loc: NW Wisconsin

I'm truly happy with 6d2, things I like are the "ease of use", flip screen, and camera is bit smaller and less weight then prior 7d2 which was great camera but 6d2 has been so much more fun to use.

Resqu2 Loc: SW Va

I sold my 5d iv and bought the Canon R and I absolutely love it. Mirrorless is the future so at least give it a good look before you decide.

rattydaddy Loc: Harrisburg, NC

I got my 5d IV back at Christmas. Upgraded from 7d. Its the best camera I have ever used, the full frame makes a world of difference. I have both of the lens you are talking about and also I use a 8-15mm fisheye for landscape. It gives you a totally different shot. Rent one and give it a try. I wan't wild about it the first time I tried it but not keep it in my travel bag.

anotherview Loc: California

This discussion may help you decide: https://www.kenrockwell.com/canon/6d/vs-5d-mark-iii.htm

Meanwhile, I own and use the Canon 6D Mark II camera with superb results.

Bison Bud

As far as the 6DII verses the 5DIV, if cost is not an issue then the 5DIV is indeed a no brainer. While the 6DII is a fine camera it is my opinion that the auto focus is far superior on the 5DIV and there are other differences that should be considered as well. Frankly, I own neither and have only read specs, but I would assume you get what you pay for with either model. Good luck and good shooting to all.

Kay135 Loc: Newburyport, MA

If you are about to invest into a new Canon system, have you considered mirrorless? The EOS R has the same full frame sensor like the 5D mark 4, very similar controls, and a wonderful line of lenses. The entire zoom line up at 2.8. Just food for thought.

Picture Taker Loc: Michigan Thumb

Some may say the 5DIV has been around a while but, it is my go to camera. It is the best thing going for an all around camera. The new Mirrorless are good but not as develops as the go to, get any thing you may want to use with, Canon developed for use any place and any time or condition camera.
I ended up using two cameras, the 5D first and my 7D. Both feeling and hand controls are the same so either came is the same in my hand I need no thought as to what camera do I have in my hand.

DebAnn Loc: Toronto

I went from a 70D (still using and love) to a 6D II because it was affordable. I like it very much. However, if money is no object I would go with the more expensive 5D IV.

Nalu Loc: Southern Arizona

5DIV for sure. No comparison between the two bodies. If you are interested in buying used, I have one with a battery grip I am sure at a reasonable price. Pretty good shape. It made a ton of wonderful images for me. There are others on this site how have purchased gear from me before who have been very satisfied.

Send me a private message if you have any interest.

tempest101 Loc: Indiana

I upgraded to 5d IV a couple of years ago, and I really like it. I fully agree with all the recommendations you already got for 5d iv.
My only gripe is the lack of articulating screen on 5d IV. I didn’t care much for it when buying, but now I wish I had it...especially when I want to get low on the ground to find unique angle for Spring wildflowers!

BebuLamar

Use the viewfinder on the 5D IV. It's a DSLR. Buy the EOS-R5 when it's available to use the LCD. I don't use live view with DSLR because if I use live view then why I even bought a DSLR?

tempest101 Loc: Indiana

Viewfinder is mostly what I do now, but it doesn’t help for unusual angles, especially close to the ground views!
And I am drooling for EOS R5, but cannot even dare to think of switching/upgrading at this point (financial reasons!)