If you download the high resolution picture of the brown pelican in the foreground contributed by cactuspic, and then blow up the region of the eye of the brown pelican in the foreground, you will see that the edge of the iris adjoining the pupil is very sharp. That was the point that the owner of the photo was trying to make. He is correct in his statement. The texture of the feathers are also quite crisp within the region of DOF. Criticizing his picture for issues that can be easily dealt with in Lightroom is not fair game.
Harvey

An advantage of Costco is that they will immediately reprint it if dissatisfied with the results. Dealing with an online vendor results in a major delay, and lacks the advantage of instant feedback and advice. This obviously also depends on the skill of the person you are dealing with.
DIsplaying images on a computer monitor has limited appeal. But for dedicated photographers, a print expresses a commitment and allows you to share your best pix in a manner that reflects the content. What I mean by that is that you can vary the size of the print relative to the setting, detail, visual impact you want to achieve in ways that an electronic image on a smartphone or a laptop don't always provide.

I just received a note from Costco informing me that they will close their printing facilities as of February14. Much to my surprise and delight I found that the prints provided by Costco were of high quality and very reasonable price. I have the prints mounted on a high quality foam board at a local Art Frame store and hang them in my house, and send them as gifts to friends and colleagues. The photos are predominantly of landscapes and birds in flight. The prints uniformly receive good comments from observers. They are usually adjusted with Lightroom.
I have printed images from my SONY 6000, 6500 and A7r4 as large as 20x30 inches and found them of excellent quality. The personnel were well informed and would reprint images if I was dissatisfied. The time from emailing the high resolution file to completion of the printing was often less than an hour.
The results at local printing options at places such as CVS, were not as well done or of equally reasonable cost.
What other printing facilities do our readers suggest?
Harvey
San Diego, CA

As suggested, the San Joaquin Audubon preserve on Riparian way, off Campus Drive near Univ Calif. Irviine, is an outstanding location for grebes, white pelicans, vultures, black skimmers, cormorants, egrets, ibis, stilts, swallows, sandpipers, etc., as well as many species of passerines of great variety, etc. One of the best places for birds in flight in Southern California. Lovely spot, quiet, great location for contemplation. Bring tripod, gimbal head, water and snacks. Park next to Audubon house and walk to various ponds. Nearby and also superb locatiion is Back Bay in Newport. There is an exhibit hall, excellent trails, lots various ducks, herons, egrets, etc. It is about a 10 minute drive from San Joaquin Audubon. Problem with Bolsa Chica is that it is too close to the very noisy Pacific Coast Highway. No sense of peaceful solitude. A large part of the reserve is blocked off by a chain link fence, making use of telephoto lens difficult. You have to stand next to the fence and look inside to photograph the birds. I have gotten some good photos there, but Back Bay and San Joaquin Reserve are much more appealing.

The MC-11 works well on my A6500 and A7R4, using it with the Tamron 100-400mm with the Canon lens connector. It is a bit slow in focusing, and sometimes fails to focus in dim light, but that is probably a reflection of the design of the Tamron, not the Sigma MC-11 adaptor. All lens operations function correctly- i.e. speed, aperture, manual focus, autofocus.

I had read (somewhere?) that 35 mm Kodachrome ISO/ASA 25 was equivalent to about 20 megapixel. The resolution declines as the ASA/ISO goes up. Don't know how reliable that number might be. Does that include calculation regarding the Beyer Mask. The Beyer Mask of a 24 megapixel chip is actually a confusing calculation, since that 24 megapixel chip is composed of 12 MP of green, 6 MP of Red and 6 MP of Blue. Since we were taught to think of a pixel as single cell representing R, G and B, the 24 MP chip is actually somewhere around 8 MP, but a bit higher if the image is rich in Green. What is the nominal number of "RGB true" pixels? Can anyone clarify this?
This problem was part of the motivation to develop a "Pixel Shift" camera, as in the SONY A7R4, where every "pixel" is a true RGB representation. Since the chip is acquiring a 14 bit depth dynamic range for each color, does it average the two green values of the Beyer Mask? Or does it retain the individual green cells of each "pixel".

In what ways does the new Canon "blow the SONY out of the water"?

Suggest that you first practice a) finding Jupiter and photographing it; b) now shoot to get pix of the moons of Jupiter. Start tonight and practice several nights prior to the desired event. It will make you feel like Galileo!
Shooting with a SONY 200-600 mm lens, I was able to capture pictures showing the four readily visible moons, and on another night could see their position had shifted and only three moons were seen. But even under these conditions, the planet will look a bit blurry. You should be able to see some limited detail on Jupiter. Mandatory to use a very sturdy tripod and remote shutter cable, with a high resolution camera. Experiment with different exposure settings. Try various ISO settings. Try to keep exposures short, as even these planets move quickly enough to contribute to blur. I don't have a GPS driven motorized telescope, which would be even better. An APS-C with 20-24 megapixel (such as the SONY 6000, 6500), or a cropped full frame of equivalent resolution such as the SONY A7R4 with 61 MP. (The APS-C frame of the A7R4 is 26 MP). Shoot in RAW mode for best resolution and ease of editing.

The major change overs were film to digital formats. I first used 8 x 10 film in the 1960's. Nothing came close in terms of resolution and dynamic range. I began to shoot pro images in the lab in digital format in 1990's, and would never go back to film. My current digital images are often in excess of 80 to 150 gigapixels (and more).
But for personal pix I continued to shoot film until the early 2000's. The immediacy of digital images was preferable, so I shifted. The ability to shoot hundreds of pix of birds in flight and throw away the (many) crummy images was economically undeniable. Mirrorless has helped improve that ratio, but the quality of the photographer is more important.
The era of DSLRs was initially limited in resolution and dynamic range. Not true any longer.
Resolution and internal image processing were consequent to improved chip design and digital processing advances.
The differences between DSLR and Mirrorless are reflected in weight, live view quality with improved EVF and representation of real time mods to shutter speed, aperture and ISO.
This is of variable importance, depending on subject material and where and how you shoot.
Overall, the market for stand-alone digital cameras has fallen by as much as 80%, regardless of whether you use DSLRs or Mirrorless, and depending on who you believe. Smartphones have captured the market, and there are many new generation talented photographers shooting very high quality images with the camera that is part of their smartphones.
I personally can't manage to hold my smartphone steady enough for good shots, and can't get decent photos of birds in flight with an iphone, but friends who have mastered flower and landscape pix on iPhone skill take superb photos.
I went mirrorless once EVF (electronic view finders) proved satisfying. But as my photo ambitions increased, I ending up with lenses that were so heavy that the difference in weight between Mirrorless and DSLR were insignificant.
You pays your money, and you takes your chance!

I have wondered what might be the best way to send gift photos to family members across the country. One method I have toyed with is to send a printing order to a Costco store near where the people live. If the printout is reliable, perhaps the family member could pick up the print at their nearest costco print center. But how consistent are the results likely to be?
My concern is that a lovely 20x30 print might easily be damaged during shipping, especially during the Xmas rush?

I think that the 6500 also has IBIS (in body image stabilization).

When shooting birds, I had been using an A6500. It is an APS-C sensor with a 200-600 mm SONY lens. The sensor provides 24 MP and allows extensive cropping while retaining sharpness. When comparing the A7R4 to A7R3, a major determinant of my decision to go with the A7R4 was that it was the only full frame that could match the resolution of the APS-C mode. It was slightly greater than the A6500 with 26 Megapixels. It is a simple step to switch the A7R4 from Full Frame to APS-C in the event that you are close enough to the bird to fill the resulting image.
The A7R4 is also improved in ergonomics, which proved enough of an attraction to influence my decision. It has recently been reduced in price.

I have only begun to explore focus stacking on my A7rm4, but have some early suggestions.
I have been experimenting with the A7RM4 in conjunction with an 18-105 mm PZ lens and using the RMT-P1BT blue tooth remote controller. The SONY unit is a bit pricey at $78. A unit with purportedly similar specs is made by JJC and available from Amazon for only $29. I have only tested the SONY unit. The JJC unit received poor reviews on Amazon. The SONY unit works well and consistently, as expected.
The minimum focus distance used was limited to about 24 inches.
The remote control device eliminates shake due to movement associated with manually pressing shutter release. It also allows you to remotely change the focus point in small increments, then shoot photo at each focus point.
On the camera: Turn on the blue tooth function under the Menu/Network2/blue tooth settings/On.
Pair RMT-P1BT to camera.
On RMT - Unlock slider button; set Zoom/Focus slider to Zoom
Set Camera to Manual Focus
Zoom lens to 90mm.
Set RMT Zoom/Focus to Focus mode
Manually approximate focus with front lens ring
Now begins the fun
Press the +/- buttons to focus back and forth. See the changes on the screen or through the viewer.
Once familiar with the operation of the RMT, take a stepped series of photos by pressing the focus button once, then shoot photo, repeat focus with a single brief press and shoot again, etc., to do an extended focus series. Needs a bit of practice, but works nicely. Provided a closely spaced step series of focus bracketing.
I have not yet figured out what the minimal step size might be. Obviously requires a lens with built-in focus motor. Will not work with purely mechanical focus lens, such as the Venus Laowa lenses.
The SONY RMT-P1BT works well on the A7RM4, but will not work on the a6500. The 6500 does not have that same blue tooth capability. Supposed to work with the 6600. A73 requires firmware update.

You should be able to then process the focus series using Photoshop.

Excellent advice about finding a unit with wheels. But I couldn't find one that had wheels and also had good weight carrying capacity/ergonomics of a well designed backpack.
Which brand and model did you find that did both? Most of the units with wheels were more like a suitcase with added shoulder straps and flimsy hip belt.

I selected a ThinkTank 26L. Very well made, good design for an elderly backpacker. Excellent shoulder straps, hip belt. Clip camera to shoulder straps to relieve burden on neck. Holds SONY 200-600 mm telephoto with attached A7r4, spare 6500 body, various lenses, cleaning supplies, remote release, raincover, etc. Separate access to rear pocket holding both a 15" laptop and a 10" iPad. Two neat methods of carrying monopod or tripod with gimbal. Pouches for water bottles, rain jacket, snacks. Backpack weighs about 3.5 pounds. Excellent comfort for longer walks. Total weight with all gear is about 25 pounds. Well balanced despite full load, even with monopod+gimbal.
Go to their website for videos on their different models. Price was about $220. A bit higher than others, ((LowePro, etc), but still within a reasonable price range. Very well padded to protect camera gear. Have not been on a plane in many months because of COVID, but it should fit in overhead rack and qualify as carryon.
None of the various backpacks I tested were sturdy enough to use as a small field seat for long days of shooting in a marsh.