How to lock focus on D3500?

[blackstar]

Nick,

Thank you for your candid and admirable testimony on BBF. I hope I can enjoy using this technique too.

Just another simple (for you) question: For stationary subject, after you press BB, do you release or hold it for recomposing? For moving subject, after pressing BB, to track I assume you would hold it and follow the subject until it's in view of your favorite. Then will you still hold or release to take a shot (press shutter)? Due to a lack of time and situation, I have to make imaginative experiments with only theory but no verification or confirmation. Please share and help.

 

[nickt]

For a stationary subject, you must release the button when you recompose. Otherwise it will instantly refocus on whatever the focus point lands on after recomposing. Think about what I called it above: "Power assisted manual focus". You are in control but you have the motor and the camera's sensors to help you achieve a 'manual' type focus on the object of your choosing.
For tracking, you can hold the button continuously. No need to release it, just click the shutter when ready. But you could release it if you wanted too. When I shoot macro, I usually hold the button down forever. The continuous focus keeps up with my wobbling. But sometimes, I take focus and release the button then I wait for my wobble to bring the bug into best focus and trip the shutter. I use it very much like I would use manual focus, but with some help from the camera.

 

[blackstar]

Thank you so much, Nick.

That is exactly what's in my imaginary implementation. So verified and confirmed. Guess that while holding BB with the thumb, triggering shutter by index quickly and steadily would need a lot of practice and good hand though. Difficult my old, weak hand would say.

 

[Bob Blaylock]

Say I use MF or AF to focus a subject and I want to lock focus ring to that distance. Is there a simple way to lock focus from that point? (AE-L/AF-L is way too much for me to use, especially the button need to be pressed all the time. I need free fingers all the time after focus locked

I wonder if I use MF to focus on a certain distance and then move the camera to other position, angle, or rotate, etc without touching the focus ring and zoom, what chance is that I would lose the previous focusing point?

Appreciate all the answers and helps.

When I want to do that with my D3200, using the lens that came with it, what I do after getting the lens to focus is, on the camera, to set the focus mode to manual, but leave the focus mode switch on the lens set to auto. This way, the lens stays locked where it is focused, only allowing itself to be changed by the camera, but the camera is set not to try to change it.

I would assume that the same technique should work, just the same, on the D3500.

Assuming the D3500 is the same as the D3200, as far as this is concerned, here's how to do it…

First, push this button:

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Next, select this menu item:

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Then select MF.

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The camera is now set to manual-focus mode. It will not attempt to autofocus, it will just take the picture, leaving the lens focused where it is.

Leave this switch on the lens set to A, and it will effectively lock the lens where it's focused.

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[blackstar]

Thanks, Bob.

The kit lens (18-55mm) came with your D3200 is nice to have focus and VR switch on it. And the way you (suggest to) use to lock focus sounds straight and simple. Unfortunately, no either switch can be found on my two kit lenses with D3500.

However, after reading your reply, I tried re-thinking this over and thought isn't it the simplest way to lock focus: Just use MF to focus an object at hyperfocal distance leaving focus ring and zoom ring untouched and turn to the night sky to shoot stars (at infinity). But this can work only if nothing (including camera itself, focus ring itself, moving camera position, etc.) would change or move focal point after HF distance is focused. Can anyone verify and confirm this? Thanks

 

[cwgrizz]

Thanks, Bob.

The kit lens (18-55mm) came with your D3200 is nice to have focus and VR switch on it. And the way you (suggest to) use to lock focus sounds straight and simple. Unfortunately, no either switch can be found on my two kit lenses with D3500.

However, after reading your reply, I tried re-thinking this over and thought isn't it the simplest way to lock focus: Just use MF to focus an object at hyperfocal distance leaving focus ring and zoom ring untouched and turn to the night sky to shoot stars (at infinity). But this can work only if nothing (including camera itself, focus ring itself, moving camera position, etc.) would change or move focal point after HF distance is focused. Can anyone verify and confirm this? Thanks

That will work. Many use that method and even use a small piece of tape to hold the focus & zoom rings in place until after they take their shots. Set up in the daylight and fix it for your night shots. If you are shooting the stars, set your camera up for the hyperfocal length in the day time. Tape the rings. At night take your camera back out and shoot. Set your tripod up close to where you had it before. A few feet one way or another when shooting stars shouldn't make any difference.

 

[blackstar]

Thanks, Walt for confirmation.

I kind of dislike using tape... Anyway, I plan to do the HF thing in the night and before the star shooting because I would probably want to shoot scenic photos even sunset before dusk during the camping trip. Hopefully, the locked HF point can stay intact while turning to the sky in a short span... BTW, I already acquired some night gears needed for night shooting (e.g., headlamp).

Ok, now let's compare this basic MF method with BBF: MF needs real manual focus skill and BBF has an advantage of speed (fast automatic focus) but may lose on sharp edge? What's your verdict in line with your experience? Appreciate your input.

 

[hark]

In one of your other threads, Moab Man gave you info on hyperfocal distance (your moon thread). If you have a smart phone, consider downloading the app Simple DoF. You can enter your camera model, the focal length of the lens being used, and the aperture. Then you can play around with the distance where you are focusing (how far into the scene you are placing your focus point). The app will give you the info on what's in focus. It also lists info on hyperfocal distance.

 

[nickt]

Ok, now let's compare this basic MF method with BBF: MF needs real manual focus skill and BBF has an advantage of speed (fast automatic focus) but may lose on sharp edge? What's your verdict in line with your experience? Appreciate your input.

Nothing better or worse in my opinion. Depends on your eyes too. I'm getting older and need reading and distance glasses. Nothing terrible, but at any given time, I might have distance glasses on or reading glasses or no glasses. My viewfinder is tweaked for my eye with no glasses but I don't always want to remove my glasses. So I can't really trust that what I see through the viewfinder is perfectly manual focused. I have to look at the camera's focus confirmation anyway. With bbf, I can take my focus anywhere I put the single point and then recompose. I don't have to trust my eyes or glance to the focus confirmation. Back in the films days, I had a split prism focus screen so it was much easier to manual focus. I had better eyes back then too.

 

[blackstar]

Thanks, Cindy. I already have PhotoPills for HF and other info.

Thanks, Nick. You may have the point on BBF over MF for "glasses wearers"! I myself wear glasses too and always feel it a troublesome burden when shooting (especially focusing) with a camera. My viewfinder is adjusted with my distance (progressive) glasses though as I usually wear distance glasses all the time (except sleeping) during a trip. At home, it's reading-computer glasses, distance glasses, or no glasses at any instant. So I may take that use BBF for most situations if I can get used to it comfortably and naturally.

 

[blackstar]

Ok, after several experiments and tests, I have come to the conclusion on focus for (at lease) my case. It turns out Nick is right about whether D3500 provides full BBF function. It doesn't -- whenever there is nothing or nearly nothing (e.g., empty wall, empty sky even with high cloud or dark sky even with bright stars) in view, shutter won't fire! So BBF with D3500 won't work for my planed star-shooting. However, BBF will be used for most of the other shootings for me. I have decided to use MF (thanks to Walt's suggestion) with hyperfocal distance for night-sky shooting after two-night trials. The first night, I was wrong to use a lighting subject for HF and got all stars out of focus... Next night, I used a non-lighting subject to make HF and the outcome is acceptable (for the test) if not great due to immense light pollution in the area.

 

[blackstar]

From my star-shooting experiment, I can say higher iso will get more stars in view, but also brighter sky due to light pollution. I guess it can edited toward darker sky with same number and brightness of star remained? But I doubt increasing exposure (by post processing) of the low iso image (darker sky) will not bring up star quantity? Thanks for comments.

 

[nickt]

Ok, after several experiments and tests, I have come to the conclusion on focus for (at lease) my case. It turns out Nick is right about whether D3500 provides full BBF function. It doesn't -- whenever there is nothing or nearly nothing (e.g., empty wall, empty sky even with high cloud or dark sky even with bright stars) in view, shutter won't fire! So BBF with D3500 won't work for my planed star-shooting.

Bummer. I had a feeling it wasn't going to work out. There was a chance they could have added it though. My d7200 and others have menu items a1 and a2 to define if af-c and af-s wait for focus (focus priority) or if anything goes (release priority). For bbf to fully work you need release priority on af-c. On the d7200, the firmware recognizes that you have set the bb to af on and it then forces release priority for af-c regardless of how the a1 menu is set. No reason other than marketing that they could not have added that feature to your camera. The d5000 could not do release priority but they added it to the d5100.

 

[Needa]

Ok, after several experiments and tests, I have come to the conclusion on focus for (at lease) my case. It turns out Nick is right about whether D3500 provides full BBF function. It doesn't -- whenever there is nothing or nearly nothing (e.g., empty wall, empty sky even with high cloud or dark sky even with bright stars) in view, shutter won't fire! So BBF with D3500 won't work for my planed star-shooting. However, BBF will be used for most of the other shootings for me. I have decided to use MF (thanks to Walt's suggestion) with hyperfocal distance for night-sky shooting after two-night trials. The first night, I was wrong to use a lighting subject for HF and got all stars out of focus... Next night, I used a non-lighting subject to make HF and the outcome is acceptable (for the test) if not great due to immense light pollution in the area.

blackstar, What version of darktable are you using and are you shooting RAW? You may be able to create a parametric mask under the luminance tab in the exposure module and increase the exposure of only the stars.

 

[blackstar]

Hi Needa, Thank you for your advice.

I use DT2.6.3 the latest version I think. For the night-sky experimental shots, I made RAW & jpg. I'll try the luminance mask as you suggested and see how far it goes. I very much appreciate your prompt tip and help for my needs and learning.

 

[blackstar]

@Nick,

It's ok as long as I find the way (use MF) to shoot night-sky effectively (still learning to master MF with viewfinder especially in night time). BTW, I can still and will use BBF for most other shootings as I find it a great technique to use. So thank you for tipping and teaching me with BBF (if not from you, I may never get to know and use it).

 

[Needa]

Hi Needa, Thank you for your advice.

I use DT2.6.3 the latest version I think. For the night-sky experimental shots, I made RAW & jpg. I'll try the luminance mask as you suggested and see how far it goes. I very much appreciate your prompt tip and help for my needs and learning.

Another way might be to increase the exposure, then use the zone module to move the black point. By selecting the last 2 or 3 zones (left, as you mouse over each zone it will show the affected areas) and moving them to the left it will re-darken the sky. YMMV with these techniques.

 

[blackstar]

Needa,

I tried the parametric mask by changing output/input. It seemed nothing happened... So I just changed the exposure and black level. It seemed working and bringing up more stars:
Before:


after:


And the high iso:
before:


after (quite more editing):

 

[Needa]

Parametric masks be sure you turn on the mask in the lower right corner so you can see how it is being applied. Some techniques work better for certain photos than others. Remember the better you get in in camera to start, the better the final product. Keep at it.

Link for some darktable videos.
https://www.youtube.com/channel/UCngiFhMSngeFwUGtsXA-17w