Image quality, looking to upgrade to EOS-1D X Mark II or EOS-1D X Mark III

[JOE929]

Hello, I’m currently shooting with the original 7D with an original EF100-400 L. I love this camera and it has treated me well. I primarily shoot air shows for my personal use. I am looking to upgrade and am looking for advice about image quality. I have rented the 5d mkiv and the IQ is so much better than the 7D. The issue is that it’s slower than the original 7D. I was considering the 1dxmkii or even the 1DXmkiii. Used they are about $1000 difference between the two. With the iii having a slight advantage with more focus points and a newer processor. Is the IQ of these cameras similar to that of the 5Dmkiv, albeit with less MP? I was also looking at the R6mkii, however, I heard that the original EF100-400 doesn’t work well with the mirrorless cameras. This would require me to add a new lens as well. Is there an appreciable difference in IQ vs the 1DX cameras? I don’t mind spending more money to replace camera and lenses, I’m just on the fence as to what’s best for my needs. I don’t want anything higher, such as a R5, I would have been satisfied with the 5Dmkiv if only its shutter speed was faster, but would like full frame over a crop sensor like the R7. I only plan to shoot with the mechanical shutter to avoid the jelly blob (so I read) as I’m mostly panning my shots. Thank you for your thoughts.

[johnrmoyer]

Since you seem to like EOS 7D, have you considered EOS R7? An ornithologist acquaintance uses it and gets very good photos of birds.

I use EOS R5 with EF100-400mm f/4.5-5.6L IS II USM +2x III and adapter. 

Not an aircraft, but flying (hand held and panning ) :  https://www.rsok.com/~jrm/2025Nov25_Salt_Plains_NWR/2025nov25_crane_IMG_5042c.html 

Sandhill Crane (Antigone canadensis) at Salt Plains National Wildlife Refuge in Alfalfa County, Oklahoma, United States on November 25, 2025

Camera Model Name	Canon EOS R5
Lens Model	EF100-400mm f/4.5-5.6L IS II USM +2x III
Focal Length	800 mm
Exposure Time	1/800
ISO	1000
F Number	13.0
Camera Temperature	26 C
Measured EV	13.88
Measured EV 2	29.5
Focus Distance Upper	114.01 m
Focus Distance Lower	81.91 m

[SignifDigits]

If it were me, and today, and for air shows, on something of a budget and not needing the daily reliability of the DSLRs, I would recommend refurbed R6 Mark ii and a refurbed RF 200-800 for better reach over the 100-500.  Or keep the EF 100-400 on a Canon adapter and rent and try the 200-800 vs 100-500 until you decide.  I've had to replace the MF dial on my R6 Mark II and I'm not a daily pro but a hobbyist so I can see why some might have reliability concerns.  You CAN set up the R6 Mark II to have the sensor exposed during lens changes, but that is not the default setting.

Of course both are available as refurbs today and I feel that refurbished is better than new since the unit has been individually tuned and hand-tested.

As John points out the APS-C is a good way to go to get longer reach, so those are options, as well.  Air shows I don't think you'd need the IBIS in the R7, and I prefer the R10 controls better at a lower price point.

[JOE929]

Thank you for the advice. I’m not sure which way to go. I am more undecided now, it seems that the 1dx’s are solid work horses but the R6’s are the future. Either way, I’m looking at over $5k(refurbed)for a new setup. I want the best bang for the buck, with sharper images. I honestly don’t expect to upgrade again as I plan to retire in a few years. The 7D works great, just need more fps to miss less shots. Thank you

[SignifDigits]

Whatever you do, in my opinion, CAREPaks should be added to your budget.  Newer gear is newer and higher tech and more tech is in them so more things to go wrong.  I didn't buy one for my R6 Mark II and just spent over $500 on a repair, which, likely would have paid for the CAREPack and I'll still have it under warranty.  I've bought them for other items, but my cameras have all not had issues in the past, so I gambled and lost.

[shadowsports]

You guys all know that I'm a CarePak advocate.  I buy them on New and Canon refurb gear. 👍

I know they're not always high on people's lists after the expense of a large purchase, but boy are they worth it.

[Steve_B]

I have the DXii and a Mk1 100-400mm lens, and recently aquired a Mk1 500mm F4. Yes, the 100-400 is 'elderly' but it's still good glass. I know it's personal preference but my DSLR bodies will see me out, I have no desire or need to go mirrorless (My background is film anyway). My close friend has a highish end Canon mirrorless body and it isn't close to the heft of the DX bodies. If I ever lose my hammers I can use it to knock in nails! But obviously it comes with the weight. 

I freely admit I'm a bit of a ludite when it comes to photography, my professional background for nearly 25 years was in the printing industry so I've seen hundreds of thousands of images. And frankly (in my humble opinion) too much is made of technology for it's own sake. 'This body has five zillion mega pixels'. 'This glass goes to f/0.0005 and can go to angstrom levels of rendition.' And as has been said, photography isn't a cheap hobby if you get into it seriously. 

Obviously it's your decision, but I would look (and they're out there-ask me how I know) at a hardly used ii or iii and try the 100-400mm before buying newer glass. If you need to, fair enough, but if you're happy with what you're shooting then stay as you are. Butterfly and hummingbird taken with 100-400mm and DX1 ii. 

[JOE929]

Thank you Steve and everyone for your support and advice. I was leaning towards the R6mk3 as new it’s roughly the same price as a used 1DX3. I hear horror stories about rolling shutter, so I’m thinking mechanical shutter only. I have to think about what is best.

[March411]

Joe the R6 MkIII will not disappoint and neither will the R6 MkII and the rolling shutting is the exception and not the rule. If you look at other mirror-less bodies across most popular brands you'll find that most if not all have some small challenges with rolling shutter. I would guess that I shoot about 80% with Electronic 1st-curtain and rarely have challenges, I've shot thousands of frames and have probably only had a handful of frames with rolling shutter impact.

That being said it may be worth looking at the functionality you want from a body (DSLR vs Mirror-less) and purchase the body that meets most of your requirements. There are going to be compromises so grab the body that comes closest to your needs and style.

If you go mirror-less and own EF lenses they will work great on a Canon mirror-less body. I shot EF lenses for quite some time as I transition to RF glass. Again, there will be some compromises like reduced burst rate on some lenses but most perform well.  

Your 100-400L Mk I does not support full burst but will still perform well on an R body. Here is a link for information on EF lens compatibility: Canon Supplemental Information 

If budget is a consideration take a look at the RF100-400mm, it will replace the focal length that you own and are familiar with shooting. It will provide you with some fine images. The frames below are the R6 MkII and the RF100-400mm taken in some pretty low light in dense timber. 

Three-toed Sloth-2.jpgClay-colored Thrush.jpgButterfly.jpg

R6 MkIII RF100-500mm

62027 Rusty-margined flycatcher BIF.jpg62265 - Adult White Bellied Spider Monkey.jpg

[TomRamsey]

Personally, I recommend going with the newest technology that fits your needs and budget.  A couple years ago when I bought my R6II and 200-800 lens I actually looked into what I needed, then set my budget to the kit, got free credit and paid it off within a year.  I wanted the lens and wanted the camera that paired it best for me, and I am completely happy with my choices.  You are kind of doing that but with an older lens.  I would look into replacing the lens also. 

[johnrmoyer]

With an APS-C sensor, only the center part of the lens is used which is usually the best part. The old lens will not be any slower on a mirrorless camera than it was before, but will not focus as quickly as a newer lens.