Shooting under fluorescent light - focus?

[CommanderJameson]

So the only thing I've taken pictures of since new year's day is the computer cabinets I installed this week.

I've come to the conclusion that computer equipment rooms are nasty places to do photography; fluorescent lighting, cramped, the subject is very bright (blinky lights!) and very dark (the bits recessed in the cabinets) at the same time, etc.

Camera (550D) was on the tripod, 2 sec delay, f/16, fluorescent WB, lens hood on. Using the 10-22mm to fit the whole thing in, probably a metre or so back.

Here's a 100% crop:



Does this look acceptable to you? Am I whining about nothing? If not, what am I doing wrong?

[14-7]

Doesn't look bad to me for a 100% crop.

[K12beano]

CommanderJameson said:

Does this look acceptable to you? Am I whining about nothing? If not, what am I doing wrong?

Hmm?!? Difficult to tell from just one shot!

Here's my tuppence, sorry if these "ideas" are a bit obvious:


First, I would think that with close-up shots at 2s you really need to have your technique at its best. So pay attention to getting the tripod as stable as possible and use mirror lock up and cable or timer.

Second, try out a range of shutter speeds. That way you can start to rule out camera shake (even if for your test shots you don't get everything in focus) or see that you are still having camera shake at certain speeds (A bean bag placed over the camera and lens can dampen down mirror aftershocks!)

Next, pay attention to your focus point to get best depth of field (but don't stop down past the point where diffraction begins to show - was a bit of a shock when I found my camera would display this at f/11 - Nikon, so I have no idea what the Canon range does!!). But also, what is the sweet spot of your lens (usually stopped down 1 to 2 f/ stops before it would start to deteriorate gradually again).

I assume you are manual focussing, but a) have you got a small viewfinder/screen making it difficult, and if so b) think of focus bracketing (i.e. shifting your focus very subtly over a series of shots which you can then properly assess on a big screen for best). Otherwise the rear viewfinder on latest dSLRs is a godsend!

If Fluorescent lighting is troublesome yet critical, consider Custom WB or stick a grey card in your test shots for later setting in PP. Although, WB is a secondary issue to your main question.

[LongQ]

So, CJ, where do you think you have problems?

Did you shoot RAW?

Is the cropped example for an edge or the centre?

2 sec delay may not be beneficial without mirror lock (if the crop image is taken from the centre)

My DoF calc program suggests that at 12mm (trying to avoid a little of the distortion), f8 with subject distance at 1 mtr the near focus limit is about .49m and Dof infinite with hyperfocal distance at .959m.

At f16 it's .327m and infinite and hyperfocal distance is .486m.

What is your primary pbjective here? Would it justify taking the images in sections and stitching (for example)?

[CommanderJameson]

RAW + JPEG (the crop is from the JPEG, not at the edge but not at the centre either).

I didn't lock up the mirror (doh).

The problem is that I think the shots are a bit (a lot) soft.

That particular frame was at 19mm, F/16 for 6 seconds.

[LongQ]

CommanderJameson said:

RAW + JPEG (the crop is from the JPEG, not at the edge but not at the centre either).

I didn't lock up the mirror (doh).

The problem is that I think the shots are a bit (a lot) soft.

That particular frame was at 19mm, F/16 for 6 seconds.

Hmm. Would mirror lock make any real difference on a 6 second exposure of this type?

I think you need to look at the RAW file for both WB adjustment (which sort of looks K to me sitting here but I have no reference point to judge against.) and to see what can be done with sharpening.

If this is in a computer room with a suspended floor, especially an operational room, you may not be able to guaranteed the no vibration makes it through the tripod in 6 seconds. If you are really diving deep into the pixels even very slight movement could look soft - but then it might be a diffraction issues at f16 too.

I think I would try:

open up to at least f8 which should be somewhere near the lens sweet spot.

Reduce the shutter time accordingly.

Get some fill light into the shadows in the boxes.

At 18mm and f8 my Dof calculator (doesn't have 19mm specifically) gives a near focus limit of .682m, DoF of 1.187m and Far Focus at 1.87m with subject distance of 1m.

If you really feel the need for more DoF try f11 or something between the f8 and f11.

Some diffuse fill flash, one or two stops belo ambient would probably pick out the interior details nicely without noticable affecting th main exposure but I would be tempted to try and eliminate as much overspill as possible just in case. Or, to put it another way, get the light just in the case.

Others with direct experience of doing portraits of server installations may have more valid and useful ideas!

[K12beano]

No - MU won't probably help at 6sec. I guess I may have misread. I was thinking about 1second down to about 1/30th at that angle of view and fairly close, LQ.

[CommanderJameson]

I'm pretty happy with the WB, tbh. The camera usually does a decent job of getting it right.

Next time I'm there I'll try a wider aperture as you suggest; I was trying to get the front and back of the equipment in the cabinet in focus.

Reading around, f/16 is way too stopped down for this lens. f/8 sounds like it might be the sweet spot.

[LongQ]

CommanderJameson said:

I'm pretty happy with the WB, tbh. The camera usually does a decent job of getting it right.

Next time I'm there I'll try a wider aperture as you suggest; I was trying to get the front and back of the equipment in the cabinet in focus.

Reading around, f/16 is way too stopped down for this lens. f/8 sounds like it might be the sweet spot.

Ah, OK, as you had mentioned WB in the list of settings and then introduced the rather 'generic' "Does this look OK ...." question I took it to mean you had concerns. Looks OK to me too. You might have a few WB issues if using fill flash but so long as you are just picking out detail a tad and the interiros stuff is generall dark material it oought to be OK. If not gel the light to match the ambient source.

The DoF values suggest you will, pretty much, get all the cabinet depth in focus at f8 I would have thought - but I'm guessing how deep the cabs are. If you want any rear vents pin sharp that may be a bit of a challenge. Focus stack and merge in PS?

[LongQ]

K12beano said:

No - MU won't probably help at 6sec. I guess I may have misread. I was thinking about 1second down to about 1/30th at that angle of view and fairly close, LQ.

I thought you may have assumed a shorter exposure.

Might make a difference at 6 seconds of the image contained light trails or similar.

Either way a solid tripod, preferably weighted, would have to be a sensible approach on a (presumably) suspended floor - anything to dampen machine induced vibration. I'm sure there could be more exotic solutions but that might be going too far for CJ's needs.

Shot at a greater distance it might not matter much but close up I would think there is some potential for just enough movement to induce softness especially on a long exposure like 6 secs.

[Simpo Two]

I don't see any camera movement there. I'd just put in it in PS and sharpen the fker

DOF at 19mm on a crop camera is very good, f5.6 would probably be adequate.

[rottie102]

Simpo Two said:

I don't see any camera movement there. I'd just put in it in PS and sharpen the fker

+1

You are all geeks!

[K12beano]

rottie102 said:

You are all geeks!

At least we're not s