D5100 Autofocus and suitability for fast action sports

[Samsonite]

Hi All,

Ive used my D5100 for about 4 or 5 different motorsport events so far this year, the majority of photos are acceptably sharp, but I do get a few shots where the focus is off, and very soft. At first i thought it was technique and using cheap lenses (Kit lens). Ive shot the last 3 races with my 70-200 F.8, and i still get a few photos which arent sharp, Im using continuous autofocus, with continuous shooting. I have tried all different focus types from single point, to dynamic and even 3D focusing, but still get some images which are out of focus, and its really frustrating, (Out of about 1000 shots per race, there are about 50 shots which are sharp).

Speaking generally, is it possible that this is due to the D5100 being an entry level, cheap camera, which is not suited to high speed motorsport photography? I dont think its a defect, because I have got some wonderfully sharp images in other scenarios, such as long exposures at night etc etc, but when it comes to high speed action, it just doesnt deliver consistently. Also, is the lack of an internal focus motor another possible issue? IE, do bodies which have built in focus motors generally tend to give more consistent and sharp results?

Thoughts and Help appreciated!

 

[Somersetscott]

Stock/kit lens are usually up to most jobs.

If you post your problem pics and settings used you will receive more in depth and helpful feed back.

There are a few tricks, like autofocus trimming per lens, picture Sharpening in camera (picture settings menu), general settings, techniques for fast moving etc etc.

What mode do you shoot in? - manual would give you all the control you need, but takes an incredible amount of patience, trial and error. So best to get it cracked before an event than during and risk missing the action.



Sent from my HTC One X using Tapatalk 2

 

[Samsonite]

I shot manual, shutter speed varies anywhere from 1/500 - 1/2000 depending on lighting. It dont believe its an issue with incorrect settings, as 95% of the shots are fine, I think its just that the AF motor isnt fast enough... will try get some examples up...

 

[Rexer John]

For motor sports I'd chose manual focus. Chose an aperture that will give the desired depth of field (providing the shutter speed is acceptable)
Focus on an object the same distance that the car will be when you intend to shoot.
Pan to follow the car and take a 3 shot burst or single shot as required.

Read this info about panning with VR section 3 and 4 are most relevant.

Also check your lens for front/back focusing bias.
Focus at the distance you intend to shoot and check if the depth of field is centred around your focus point.
If you find you are already focussing with a rear bias and the car is coming towards you, there's your problem.
Easy to compensate in manual focus using the dot confirmation, but still an issue that could do with correcting.

 

[Nikon Photographer]

I would suggest you set the camera to Shutter Priority, and use manual focus, learn to pan, and i'll say your success rate should improve ....

 

[Samsonite]

I dont believe its anything to do with shutter speed or panning, as the shots are head on in slow corners, how can I accurately tell if it is back focussing?


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[Don Kuykendall_RIP]

I dont believe its anything to do with shutter speed or panning, as the shots are head on in slow corners, how can I accurately tell if it is back focussing?


Sent from my iPhone using Tapatalk!

The D5100 does not have an adjustment for Back focus so you can not fine tune it.

Presetting the focus is probably you best idea. I am not sure any camera could do any better on AF than what you are getting. If I read it correctly you are getting 95%? That is a good rate for anyone in my opinion. Check to see what your DOF is for the lens / aperture / distance and make sure it is wide enough for the track and set in the correct place and shoot away.

 

[Samsonite]

Manual focus isnt really an option either because I usually shoot about 4 or 5 frames per corner, and the distance travelled is too large to be covered by depth of field, or manually adjusting focus in real time whilst shooting....

Is there a 'How to' for measuring / checking depth of field?
​

 

[Rexer John]

The D5100 does not have an adjustment for Back focus so you can not fine tune it.

It does but it's inside the camera body (a 2mm hex if I remember correctly) and shouldn't be messed about with unless the user knows what they are doing.
Adjusting correct for one lens may put other lenses off from neutral bias.

Samsonite, there are guides for checking front/back focus but they are usually centred at around 2 to 3 metres.
The easiest way for a longer distance as ion your case is as follows....
Get a static object at your focal point and have reference objects in front & behind to check depth of field.
Take a few shots in live view, refocussing each time, this is your reference using contrast detection.
Now take the same shot through the viewfinder, if they are the same as your earlier shots, your lens is focussing correctly.
If not, you could go into the camera body but it's a case of adjusting the mirrors to get the auto focussing centred.

 

[Samsonite]

Sounds complicated

 

[Rexer John]

(Out of about 1000 shots per race, there are about 50 shots which are sharp).

95% of the shots are fine

Are you saying only 50 shots out of 1000 are sharp but only 5% of the total are not usable? i.e. most are just okay shots.
Are you unhappy due to pixel peeping or is the issue actually showing on prints and/or pictures resized to fit your monitors resolution?

 

[Samsonite]

5% arent tack sharp, the rest are, they look fine on the LCD, but are out of focus when viewed on my monitor... I just assume that Pros get 100% hit rate and every single image is tack sharp.... Unless im mistaken....

 

[Samsonite]

Im off out this evening, but will be home all day tomorrow watching the Le Mans test day, will upload some examples then....
​

 

[Moab Man]

95% in focus is great! There is no issue with the focus. You have to remember your taking pictures at a high rate of speed and the camera is adjusting constantly as the object moves. Throw in the fact auto-focus works off the contrast the camera can identify. If your focus dot falls into an all white or black field then the focus will be challenged. And while you may not be focusing on an area without contrast the moving vehicle will at times cause your focusing point to momentarily lack sharp focus when it does pass through a no contrast area and then quickly recover when contrast is there again.

From everything you have posted you and the camera sound like you're doing great at a 95% success rate.

Although I am a little confused on your two posts as to whether you're getting 50 out of 1000 (not so good) or 95% of a 1000 (outstanding).

 

[pedroj]

5% arent tack sharp, the rest are, they look fine on the LCD, but are out of focus when viewed on my monitor... I just assume that Pros get 100% hit rate and every single image is tack sharp.... Unless im mistaken....

If you want pro results get a D4....I might be wrong but I doubt the pros get it right 100%

 

[Samsonite]

Out of curiosity, do the cameras with focus motors in the body have any advantage over the D5100 without the AF motor in the body?