Lighting priorities? Lumens, Color Temp, or CRI?

[Keith Avery]

I am working on lighting layout of my eventual hobby shop. I am currently planning on a drop ceiling using mostly T12 troffer style lights(craiglist bargain). I have been looking at bulbs and am not sure which ones I should use. I can get 34 watt 2800 lumen output bulbs, with CRI of 82 and color temp of 3500. This would give me the most lumens. It seems most have said to go with higher color temp though and if I go for color temp greater than 5k the lumen output drops to 2000-2200, CRI goes up to mid 80s to low 90s though. Is loosing 25 percent of the brightness worth get better CRI and color temp? If I go with 40 watt bulbs I can get 2300 lumen 6500k CRI 84. I am getting pretty confused, any help would be great.

[Jim O'Dell]

I got my T-8 bulbs from http://www.businesslights.com/ushio-...-c-81_337.html I got the 86 CRI 5000K 3050 lumen units and I'm very happy with them. I was short on bulbs for the last 4 bulb fixture I put in, so tried a couple Sylvania 95 CRI ??k units from HD, and they are way too blue for me. Gives me a headache. Might be ok at the work bench where I tinker with stuff, but not for woodworking. Look through and see what they have for T-12 bulbs. But keep in mind, many have been saying for a few years that T-12s are on their way out. T-8s and T-5s will become the norm for their energy savings. Jim.

[Dan Hintz]

CRI is only important if you intend to photograph or display your items in the shop. It may help some if you're staining and want to match color or get a good feel for how it will look outside, but other than that I see no reason to strongly match CRI... I would go for lumens at a color temperature that you feel comfortable working in.

[Jack Lindsey]

Keith, you probably don't want to use t-12's. They are being phased out by government regulators who seem to erroneously believe that source energy efficiency is paramount to saving energy. But that's a topic for another discussion. Use T-8's instead since you won't be able to get T-12 replacement lamps in the future.

You don't say what kind of shop you are planning but if it is woodworking I'm not a big fan of enclosed troffers. They get very dirty very fast in a woodworking shop. If you use lensed troffers be prepared to clean them often.

As far as CRI goes is really isn't terribly important in a wood shop since we shouldn't be matching colors with typical shop lighting. Do color selection and matching under the light source used where your work will be used. If you really want to match colors in the shop get a few color matching lamps, probably a Chroma 50, and use them where you will be matching colors. For general lighting anything above 60 is probably going to be ok. Most T-8's range from 75 to 92 depending on the color and phosphor composition. Any of them should be fine.

Color temperature is whatever you prefer. 3000K will give your shop a warm visual appearance. 3500K is neutral. 4100K is cool. 5000K is cooler. Over that is cold. 3500 or 4100 are the most common.

Lumen output is important since the higher the lumens the more light you will have. The lower lumen output with color enhanced or high color temp lamps isn't justified for woodworking.

[Charles Wiggins]

Keith,

I have a basement shop with exposed joists for the ceiling. I outfitted my shop with 4' T-8 hanging "shop lights" so I could move them around as needed. I have quad outlets mounted to the joints all around the shop and they are all on a single light switch. I can rearrange or add a light at any time just by mounting a couple of hooks and plugging in.

I filled them with Philips 5000K "Full spectrum" bulbs from HD. The color temp is not exactly "daylight" and the CRI is only 82, but they seemed to be the best compromise between true daylight quality and price that I could find. They're $34 for a box of 10 and the true daylight bulbs that I priced were twice as much or more. The quality was not consistent though. Some of the bulbs have had defects in the coating and have not fluoresced properly so I neded up exchanging a couple of boxes to get 20 good tubes out.

I prefer the T8s, even though they're a bit more expensive up front, you get more light for less wattage and they generally have a longer life.

Hope this helps,
Charles

[Rod Sheridan]

As others have indicated your priorities should be;

- T8 lamps with good quality electronic ballasts

- good lumen output

Regards, Rod.

[Jack Lindsey]

CRI is only important if you intend to photograph or display your items in the shop. It may help some if you're staining and want to match color or get a good feel for how it will look outside, but other than that I see no reason to strongly match CRI... I would go for lumens at a color temperature that you feel comfortable working in.

CRI is meaningless when selecting a light source for photography.

CRI is the correlation between the spectral distribution of a light source and the spectral dustribution of a blackbody radiator operating at the same color temperature as the light source. An incandescent lamp is essentially a blackbody radiator within the visible portion of the electromagnetic spectrum so an incandescent lamp has a CRI of 100. This applies regardless of the color temperature of the incandescent lamp. If the lamp is dimmed to a very low output the spectral emissions shift strongly into the red region and other colors, particularly blues, are significantly muted. Would you recommend the dimmed incandescent lamp to photgraph objects with blue or other cool colors? Remember, the CRI of a dimmed incandescent lamp is 100.

For color matching choose a lamp specifically made for that task - the Chroma 50 series.

[Dan Hintz]

Jack,

You're trying to pick a fight on a morning where I could not care less about fighting one... CRI is hardly meaningless in photography (and my MS degree's specialization is image processing). But whatever gets you by...

[John McClanahan]

I just went through this at work. The tubes in the 3000 Deg. K range seemed to have too much color in the light. The 4100 Deg. K lamps were much better liked. 5000 and up seem harder to find and cost more.

John

[Chris Friesen]

Personally colour temp is most important, then CRI, then lumens. I prefer 5000K...anything higher starts to look really blue. I went with the CRI86 bulbs because at the time the high-CRI Phillips ones were really pricey.

[Jack Lindsey]

Dan, I'm not trying to pick a fight. I'm simply stating a fact. If you doubt what I am saying try photographing a blue object under an incandescent lamp that has been dimmed to a low level where most of the output is red. The color of the object in the photo will look pretty bad yet the CRI of the light source is 100.

[Dan Hintz]

Dan, I'm not trying to pick a fight. I'm simply stating a fact. If you doubt what I am saying try photographing a blue object under an incandescent lamp that has been dimmed to a low level where most of the output is red. The color of the object in the photo will look pretty bad yet the CRI of the light source is 100.

A dimmed incandescent no longer has a CRI near 100... severely dimmed is not even close. Your facts don't hold up when you change conditions like that...

[Ron Alley]

The most important issue is not being discussed. Lighting in a work area should be balanced -- adequate front lighting, adequate back lighting and enough side lighting to fill in shadows.

[Barry Mabery]

As others have indicated your priorities should be;

- T8 lamps with good quality electronic ballasts

- good lumen output

Regards, Rod.

Based on my experience manufacturing fluorescent and HID for over 35 years, I think Rod's summation is right on target. No matter how cheap the CL T12 fixtures are, the reliability, efficiency, zero noise level and obsolescence-proof nature of the T8 electronic ballasts make a modern fixture much better in the long run. T8 lamps have longer rated life and a flatter output curve, so less loss over time. And in a few years you probably won't be able to find T12 ballasts or maybe even lamps.

Lighting color (i.e., Kelvin temperature) is extremely subjective. I prefer 4100*K but can just tolerate 5000*K. Daylight lamps - Barf.

Barry

[Jack Lindsey]

A dimmed incandescent no longer has a CRI near 100... severely dimmed is not even close. Your facts don't hold up when you change conditions like that...

Believe as you wish. Not worth wasting more time on it.