Low Light Gym Filming - Sony A6700 + 18-135mm

Overview

If your gym relies on overhead fluorescents with no natural light, it’s low light — and most commercial gyms fall into this category. You’ll know for sure when your camera pushes ISO above 1600 to get a usable exposure. That’s when noise becomes visible and image quality drops.

This document provides technical guidance for filming strength training in these environments. It covers exposure settings, focal length selection, common problems, and recommended solutions.

The reference setup uses a Sony A6700 with the Sony 18-135mm f/3.5-4.5 kit lens, though principles apply broadly to similar camera systems.

Scope
This guide focuses on solo documentation filming with a fixed tripod position. It does not cover multi-camera setups, gimbal work, or professional production workflows.

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Equipment Reference

Camera and Lens

Component	Specification
Camera body	Sony A6700 (APS-C, 26MP)
Lens	Sony 18-135mm f/3.5-4.5 OSS
Maximum aperture	f/3.5 at 18mm, f/4.5 at 135mm
Tripod	Peak Design Travel Tripod

Recording Settings

Setting	Value
Resolution	4K (3840 × 2160)
Frame rate	25fps
Bit rate	140Mbps
Colour sampling	4:2:2
Bit depth	10-bit
Picture profile	Cinetone
White balance	3000K (manual)

Why These Settings

25fps — Matches PAL standard for the UK/Europe. Also determines shutter speed baseline via the 180-degree rule (25fps → 1/50 shutter). If you’re in the US, use 30fps (NTSC).

Not 50fps or 100fps — Higher frame rates are for slow motion. They require more light (faster shutter speeds) which means higher ISO in a dim gym. For real-time training documentation, 25fps is enough.

Cinetone — Sony’s picture profile designed for video. Produces natural skin tones and a cinematic look straight out of camera with minimal grading. Flat profiles like S-Log require colour grading — unnecessary complexity for training footage.

3000K white balance — Counteracts the yellow-green cast from overhead fluorescents. Produces a cooler, industrial grey aesthetic. Higher values (4000K+) look yellow under gym lighting.

Recording Format Options

Option	File Size (20 min)	Use Case
100M 4:2:0 8-bit	~14GB	Recommended — good quality, manageable files
140M 4:2:2 10-bit	~20GB	Overkill for training footage unless colour grading
60M 4:2:0 8-bit	~8GB	Not recommended — visible compression in detailed scenes

What I Use
100M 4:2:0 8-bit. Good balance of quality and file size. 140M offers more data for colour grading, but for Cinetone footage with minimal post work, the difference isn’t visible.

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Exposure Configuration

Why Aperture Priority Feels Like the Right Choice

Aperture priority is the go-to mode for video in mixed lighting. You lock the aperture wide open for maximum light, and let the camera handle ISO. It works well in most situations — the camera adapts as conditions change.

In a gym, it doesn’t work.

The Problem: Auto Exposure in Low Light

Aperture priority mode with auto ISO causes exposure instability in gyms with uneven lighting. As the subject moves through the frame, the camera continuously adjusts ISO, resulting in visible brightness fluctuations during recording.

This is particularly problematic when:

• The subject moves between lit and shadowed areas
• Background brightness varies (e.g., windows, mirrors)
• Overhead lighting creates uneven illumination

Symptom
Footage alternates between bright and dark within a single take. ISO values may swing 800-1600+ between frames.

The Solution: Full Manual Exposure

Lock all exposure variables to eliminate hunting.

Parameter	Recommended Value	Notes
Mode	Manual (M)	Full control of all settings
Aperture	f/4.0	Widest available on kit lens at 24mm+
Shutter speed	1/25	See shutter speed section below
ISO	640-1000	Lock manually based on conditions

Exposure Verification Tools

Tool	Setting	Purpose
Zebras	100+	Identifies clipped highlights
Histogram	Enabled	Monitors overall exposure distribution

Procedure

1. Set manual exposure values
2. Enable zebras at 100
3. Frame the shot with subject in position
4. Adjust ISO until zebras disappear from skin/equipment
5. Check histogram — ensure data is centred, not left-weighted
6. Lock settings and begin recording

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Shutter Speed Selection

Standard Rule

For 25fps video, the 180-degree shutter rule recommends 1/50 shutter speed. This produces natural motion blur consistent with cinematic footage.

Low Light Adaptation

In environments where 1/50 requires ISO 1600+, reducing shutter speed to 1/25 provides a one-stop exposure advantage.

Shutter Speed	ISO Required (f/4, dim gym)	Trade-off
1/50	1600-2500	More noise, standard motion blur
1/25	800-1250	Less noise, increased motion blur

Motion Blur Acceptability by Movement Type

Movement	Speed	Blur at 1/25
Squat	Slow, controlled	Not noticeable
Deadlift	Slow, controlled	Not noticeable
Bench press	Slow, controlled	Not noticeable
Bent over row	Moderate	Minimal
Shoulder press	Moderate	Minimal
Press ups (fast)	Fast	Noticeable
Sprints	Fast	Significant

Recommendation
For strength training documentation where the primary subjects are compound lifts, 1/25 shutter speed is an acceptable trade-off. The reduction in image noise outweighs the minimal motion blur on controlled movements.

Fast Movements: When to Increase Shutter Speed

1/25 works for controlled lifting. It doesn’t work for sprints.

Fast movements require faster shutter speeds to reduce motion blur. But how much blur you want is a creative choice, not a technical rule.

Movement	Recommended Shutter	Notes
Squats, deadlifts, bench	1/25 – 1/50	Controlled, slow movements
Rows, shoulder press	1/25 – 1/50	Moderate speed
Fast press ups	1/50	Some blur at 1/25
Box jumps, cleans	1/200	Explosive movements
Sprints	1/100 – 1/500	Depends on the look you want

Motion Blur: Technical vs Creative

For sprints, there’s no single correct shutter speed. It depends on what you’re trying to capture.

Shutter Speed	Result	Feel
1/100	Visible blur on arms and legs	Fast, dynamic, cinematic — conveys speed and energy
1/200	Slight blur, mostly sharp	Balanced — movement visible but cleaner
1/250+	Fully frozen motion	Clinical, precise — every frame could be a photo

Fully frozen sprints can look oddly static, like a slideshow. Some blur makes movement feel real.

Ask yourself
Are you documenting for analysis or capturing the feeling? For training logs where the point is “I did sprints,” motion blur at 1/100 looks good and conveys effort. For form breakdown or coaching clips, freeze it at 1/250+.

Practical Approach

Keep two settings in mind:

• Lifting preset: 1/25, ISO 640-800
• Sprint adjustment: 1/100 for cinematic feel, 1/250+ for frozen detail

Switch shutter speed before sprint sets, switch back for lifting. Or film sprints when natural light is strongest to allow faster shutter without noise penalty.

Trade-off
Faster shutter = less light = higher ISO = more noise. For sprints in a low light gym, you may need to accept some noise or some blur. If clean frozen footage matters, time it for the daylight window.

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Focal Length Selection

Wide Angle Distortion

Focal lengths below 24mm (full-frame equivalent: 36mm) introduce perspective distortion when filming the human body at close range.

Effect	Description
Barrel distortion	Edges of frame curve outward
Perspective exaggeration	Objects closer to camera appear disproportionately large
Edge stretching	Limbs near frame edges appear elongated

Practical Impact

Focal Length	Camera Distance	Result
18mm	Close (1-2m)	Distorted proportions, stretched limbs, unprofessional appearance
24mm+	Further (2-3m+)	Natural proportions, accurate body representation

Recommendation
Use 24mm minimum (36mm full-frame equivalent). Position the tripod further back to maintain framing. This produces more accurate documentation of form and movement.

Space Requirements

Shooting at 24mm+ requires additional distance between camera and subject. In constrained gym environments, consider:

• Positioning in corners for maximum depth
• Using mirrors to check framing without repositioning
• Setting up before peak hours when floor space is limited

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White Balance Configuration

Gym Lighting Characteristics

Most gyms use overhead fluorescent or LED lighting with colour temperatures between 3500K-5000K. Auto white balance may produce inconsistent results as the camera compensates for mixed lighting.

Manual White Balance Settings

White Balance	Result	Use Case
3000K	Cool, industrial grey tones	Preferred for neutral documentation aesthetic
4000K	Neutral, slight warmth	Balanced appearance
5000K+	Warm, yellow cast	Not recommended for fluorescent environments

Note
Lower colour temperatures (3000K) counteract the yellow-green cast common in fluorescent-lit environments, producing a cleaner, more neutral image.

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Ambient Light Considerations

The Daylight Variable

Gyms with windows experience significant light level changes throughout the morning. This affects required ISO settings.

Time Window	Typical Conditions	ISO Required (f/4, 1/25)
06:00-08:00	Artificial light only	1000-1600
08:00-09:00	Mixed light	800-1200
09:00-11:00	Daylight contribution	400-800

Optimisation
Schedule primary lifts (those requiring best footage quality) for the daylight window when available. This allows lower ISO values and cleaner images without equipment changes.

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Common Issues and Solutions

Issue 1: Exposure Fluctuation During Recording

Symptom: Brightness changes mid-take
Cause: Auto ISO or auto exposure enabled
Solution: Switch to full manual exposure, lock ISO

Issue 2: Excessive Image Noise

Symptom: Grainy, noisy footage
Cause: ISO too high (typically 2000+)
Solution: Reduce shutter speed to 1/25, open aperture fully, utilise daylight window

Issue 3: Distorted Body Proportions

Symptom: Stretched limbs, exaggerated perspective
Cause: Wide focal length (18mm) at close distance
Solution: Zoom to 24mm+, increase camera-to-subject distance

Issue 4: Yellow/Green Colour Cast

Symptom: Unnatural skin tones, yellow-tinted footage
Cause: Auto white balance compensating incorrectly for fluorescent lights
Solution: Set manual white balance to 3000K

Issue 5: Wrong Recording Mode

Symptom: Settings don’t match saved presets, unexpected behaviour
Cause: Camera in photo mode instead of video mode
Solution: Verify mode dial before recording, use dedicated video mode

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Lens Upgrade Path

Current Limitation

The Sony 18-135mm f/3.5-4.5 kit lens limits low light performance. At 24mm focal length, maximum aperture is approximately f/4.0.

Upgrade Options

Lens	Max Aperture	Price (approx.)	Benefit
Sigma 18-50mm f/2.8 DC DN Contemporary	f/2.8 constant	£439	+1.5 stops light gathering
Sigma 17-70mm f/1.8 DC DN Art	f/1.8 constant	£779	+2.3 stops light gathering

Expected Improvement

Aperture	ISO Required (1/25, same exposure)
f/4.0 (current kit lens)	1000
f/2.8 (Sigma 18-50mm f/2.8 DC DN Contemporary)	500
f/1.8 (Sigma 17-70mm f/1.8 DC DN Art)	200

Assessment
The Sigma 18-50mm f/2.8 DC DN Contemporary provides good value — constant f/2.8 allows ISO reduction of approximately 1.5 stops. The Sigma 17-70mm f/1.8 DC DN Art is the better long-term investment if budget allows — over 2 stops faster than the kit lens, which virtually eliminates low light limitations in most gyms.

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Saving Presets

Why Save a Preset

Switching between photo and video modes, or reconfiguring settings each session, wastes time and leads to mistakes (like filming an entire session in photo mode).

Save your video settings as a preset. One dial click and you’re ready.

What to Save

Setting	Value
Mode	Manual
Aperture	f/4.0 (or widest available)
Shutter	1/25
ISO	800 (adjust per session)
White balance	3000K
Picture profile	Cinetone
Bit rate	100Mbps
Colour sampling	4:2:0 8-bit

How to Save (Sony A6700)

1. Configure all settings as above
2. Menu → Shooting → Shooting Mode → Memory Recall (MR)
3. Register to M1, M2, or M3
4. To recall: turn mode dial to 1, 2, or 3

Tip
Use M1 for gym filming preset. Check the mode dial before every session — it takes one second and prevents filming in the wrong mode.

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Quick Reference Card

Recommended Settings (Low Light Gym)

Parameter	Value
Mode	Manual
Aperture	f/4.0 (or widest available)
Shutter	1/25
ISO	640-1000 (locked)
White balance	3000K
Focal length	24mm minimum
Picture profile	Cinetone
Zebras	100
Histogram	Enabled

Pre-Recording Checklist

• Video mode selected
• Manual exposure set
• ISO locked
• White balance at 3000K
• Zebras enabled
• Framing at 24mm+
• Tripod stable and positioned
• Test clip reviewed

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Revision History

Date	Version	Changes
2026-01-04	1.0	Initial documentation

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Technical reference document. Updated as new learnings are validated.