Cell phones as view finders? How bad?

I am curious about everybody's experience with cellphones as view finder / rear display substitute. I am sitting on the fence concerning a new camera purchase. I want portrait zoom, sports AF and a WLF substitute to work together. From my current understanding I could maybe get the first 2 traits with an EOS 5D IV, but it has no tilting or articualted rear screen. Will cobbling a cellphone holder to the tripod collar make my day? - I own an elderly Android phone.

Questions to experienced users:

1. How long does it take to connect a phone to camera?
   
2. Can you mess with the phone's energy settings to keep the display bright while waiting for your shot to happen? (I have a Samsung Galaxy Family)
   
3. What happens when your phone fell asleep? - Do you have to reestablish the connection to your camera?
   

What would be reasons to buy a tiny portable monitor like video shooters are using?

Camera choice is up for discussion too. - I think I have to go Canon to get the nice 70-200 f2.8 and according to reviews quite decent AF even in live view or indoors? - I read other brands' 70 -200mms appear shorter at the long end when doing headshots, which sounds dissapointing.

Does it matter on what kind of smart phone one runs the Canon app?

Thanks in advance for your replies

I confess that I don't find the cell phones to work at all well as an accessory to a camera. But I'm getting old and set in my ways. I find it too hard to see the phone screen in bright sunlight, etc.

However, I have rarely used some phone apps that tell you how the light will fall at different times to plan set-ups for dawn shooting and such like.

Nice ideas, but in reality obviousy pretty useless

To begin with, what is the extra an image on the LCD of a DSLR gives you?

It shows the image frame that comes with the lens used, the DoF following the set aperture and lens used, and gives an indication of the hopefully correct exposure and color temperature (basically what back in the film days we did with NPC backs and Polaroids)

A cellphone will show you a, with the exposure and color temperature automatically chosen, rendition of the scene, not using a similar focal length as the camera (so not showing the same frame and Dof) nor using be the same exposure and color temperature you dialed in on your camerta (as far as I know there are no cell phones on the market which allow manual setting of speed and aperture, all just/only have'offer automatic exposure)

Since it most likely will be programmed to always give a 'correct' exposure etc. that of course can't be used as a valid tool to indicate whether the (completely different) settings on the camera are correct too

So while your image on the cell phone will look correctly exposed, the image of your DSLR will be different due to the difference in lens and DoF used and easily be over or under exposed and have an incorrect color temperature

I'm really amazed that you are discussing this as a serious option in connection with the possible use of a Canon 5DIV and 2.8/70--200 lens, the two of which will demand a multi thousand dollar investment while you apparently lack the most basic photographic knowledge, which would immediately have learned you this wouldn't work

If you really want an extra external monitor next to a Canon 5DIV (or any other DSLR) which you can look at from a different angle then where the LCD/camera is (eg camera mounted in a high spot whie you are standing in lower position) better look into connecting it with eg a tablet, laptop or small external HDMI monitor.

Plenty of those options around, all of which will show you the actual image (and exposure and colortemperature etc) of the camera.

And if you think that might cost too much, a Eye Fi Mobi card or similar card might do the trick.

It has a built in Wifi transmitter (transmission range max approx 5 feet), and will after you installed the app on your phone or tablet, immediately/shortly after you take a picture (in reality it might take a few seconds if you set it for sending a small format JPG) send a copy to your mobile device for your visual inspection

Based on that you can see whether your settings are correct and if you like the set up of the image (lens used, composition, details etc) and if necessary make corrections

I use Eye Fi cards all the time when shooting fashion etc in the studio and on location

Thanks for getting back!

@JDMvW : I hear you. - My clueless questions about phones probably hint that I haven't found any use for them yet. - I hoped Phone screens might be a tad brighter than what I have on an inexpensive Fuji and planned to use that thing indoors.

@paul_k : I am not sure if we are on the same subject. - To my understanding of reviews and marketing the 5D IV is supposed to have a built in transmitter that will send the rear display's live view and AF point selection touch screen functionality on i-OS or Android devices running the Canon app?

I have no intention to use my cell phone's built in camera. - So why are we talking about it at all?

While the cell phone display will surely render colors slightly differently than the camera's, the only open questions are my initial ones, since I am really not familiar with using smart phones +

• How much lag will Wi-Fi introduce to live view, compared to build in or wired displays?
  

If you really want an extra external monitor next to a Canon 5DIV (or any other DSLR) which you can look at from a different angle then where the LCD/camera is (eg camera mounted in a high spot whie you are standing in lower position) better look into connecting it with eg a tablet, laptop or small external HDMI monitor.

Plenty of those options around, all of which will show you the actual image (and exposure and colortemperature etc) of the camera.

Did you do any research on those devices that would lead to a recommendation of a specific one?

I bought an USB extension cord for shooting tethered but the cameras I currently own aren't supported by Lightroom and so far I felt getting along with my rear displays.

I have no intention to use my cell phone's built in camera. - So why are we talking about it at all?

While the cell phone display will surely render colors slightly differently than the camera's, the only open questions are my initial ones, since I am really not familiar with using smart phones +

You should have formulated your question better then.

Did you do any research on those devices that would lead to a recommendation of a specific one?

I didn't do any extensive research for personal use as I'm not interested in it, but obviously there is plenty of literature about the subject available, Nikon eg had a web tutorial on it

How to Use HDMI Video Recorder & External Monitor with HDSLR from Nikon

and Canon (and other manufcturers as well) probably has one too

As far as HDMI monitors is concerned, plenty of those around too

A simple search 'hdmi monitor for dslr' will trigger an avalanche of alternatives, from e.g. Amazon, B&H, Alibaba, eBay etc as well as plenty of reviews of them

I personally would never dare to make a statement which one is 'best', that just like eg camera brands only too often is a matter or personal taste and preference:

- Do you want one from the most prestigious manufacturer?

- Do you want the best specs no matter what?

- or do you go for best bang for money, or simply want the cheapest one around?

- should it be small, or doesn't size matter?

- do you want to go high tech or low tech?

etc etc

Best do some reading yourself to find out what your priorities for an external monitor are, I really wouldn't blindly folow other peoples advise especially with techie stuff

Otherwise ask for an answer for 'what is the best HDMI monitor for use with a DSLR' here, on DPreview, Fred Miranda, I'm sure there are plenty of 'experts' around to give their opinion