My G3 LCD is lying too me!

[FlyingPete]

I was doing some product shot work for someone last night, and as I was using a white background and the subject colours varied between light and dark, I locked the exposure into manual and metered of a grey card (also manually set the white balance as well).

As expected the camera was mostly reporting over exposures between 0.5 and 1.5 stops, but I trust the grey card!

However most of the shots looked quite over exposed through the LCD, even on reviewing them (so its not that funny little thing the G3 does when focusing that changes the brightness of the image. I still trusted in my grey card exposure readings, and since the only light source was my 'studio' lighting, there were no variations in light levels.

When I downloaded the images to my PC, they were all perfectly exposed. What gives? Can I trust my LCD for what the exposure will look like?

You can forget using manual focus of a white object on a white background with the LCD being that bright, no discernable detail, the auto focus agrees with this and also can't get a fix (solution put a darker object in the same place, and manually focus on that).

BTW, checked the LCD brightness settings, all set normal.

Also BTW, grey cards are great, even if you only use it for setting white balance! It has got me out of a lot of tight exposure spots with my EOS in the past.

[Ralph]

question:


Why do you use a grey card and what does it to you pictures??

Can you show some examples?

Thanks

[sidebp]

As far as I've been made aware - grey is a neutral colour which means its ideal for ensuring the white balance on the camera is correct.

If you were to use white card, chances are it will (to some degree) reflect its surroundings and thus give you a misreading - grey isnt so susceptible to this. For example if you were in a room with tungsten/"yellow" lighting you could take a meter reading off the card to ensure your WB was correct.

Although I may have just written one big lie! :lol: Anyone care to elaborate/correct?

Maybe its wrong of me but as long as the WB is near enough right I tend not to worry about it too much as its easily fixed in Photoshop anyway (either with Auto-Color OR by Image-->Adjustments-->Curves then clicking on the set grey point dropper and selecting a neutral tone in the picture). Obviously, if your image is massively over or under exposed you're going to have a hard time correcting it, plus (more-so) with an over-exposed image: there will be a loss of detail (for safety a lot of people I know under expose ever so slightly and then correct if needed) - in a lot of cases, a massively over exposed image is a "bin job" unfortunately!!

Kind Regards,

Paul

[FlyingPete]

A 'grey card' is used to accurately set the exposure of a camera.

Most (possibly all) cameras auto exposure systems assume that if you averaged the area being metered it would be 18% grey, this seems to work in most circumstances, but there are some exceptions, most common seems to be snow which the camera assumes it is 18% grey and under exposes the scene (some cameras have a 'snow' mode to counter this, which just 'over exposes' the scene), another example could be a very dark scene which will be over exposed.

The solution to this is an expensive light meter, or a grey card. The grey card is exactly that, a piece of card that is coloured in a neutral (not warm or cool) 18% grey. To use it you point the camera at the card in the lighting conditions you are shooting in and base the exposure settings off that either manually or useing the exposure lock (if the camera has one, the G series does, the * button) to hold the correct exposure.

I was using one, for product shots, in this case candles. Since the candles are partly transparent, it required a white background so they didn’t discolour, also my client requested the backgrounds be removed, white is fairly easy. I knew for starters that the camera would generally under exposure due to the larger white area, and I also had a number of different coloured candles, that would have all metered differently. I required the same lighting for all, so I manually set the exposure of the grey card (in this case at ISO50, 1/30s F4.0).

Another good use for the grey card is setting the white balance due to the fact that the card is neutral grey. As I was shooting under artificial light (in the case Compact fluros, as they don’t get too hot, can’t dim them though) set my white balance of the card as well.

On looking after the card, I ALWAYS put in back in an opaque cover, to protect it from fading, not much good if it faded!

Does anyone know how to measure a scene in Photoshop to see what it averages to? I think auto levels takes the lightest spot and assumes it is white, then takes the darkest spot and assumes that is black.

I will load some samples as soon as I get my FTP account working!

[FlyingPete]

Here are a couple of images these would have exposed differently had I relied on the camera's auto exposure:
http://www.lowden.net.nz/Stuff/IMG_9519.JPG
http://www.lowden.net.nz/Stuff/IMG_9526.JPG

[Flagpole]

G'day Flying Pete!

I have a story of my own but it concerns a G2 and some family pics I took few weeks back. I bought a Lumiquest ProMax System to avoid harsh shadows and deliberately decided to underexpose most pictures (flash power at -2, using a 20-80 System with bounce off the ceiling). The reason was to bring out more natural colour and use as much available light as possible (well thats the theory of course). All of the pictures looked good on the LCD but the histogram was shifted left (I decided to ignore it and go with the LCD look). When I got home the pics were badly underexposed to my surprise. I tried correcting them manually then gave up. I then used Adobe Photoshop CS raw conversion for a much better conversion. See examples below:

Original raw conversion via Zoombrowser

http://www.members.oztralia.com/~bfeldman/Testshots/underexposed.jpg

Same file corrected in levels for white/black point (no gamma correction at this stage)

http://www.members.oztralia.com/~bfeldman/Testshots/correctedlevels.jpg

And again using Photoshop CS raw conversion with +1.60 Exposure an 5500K temperature setting.

http://www.members.oztralia.com/~bfeldman/Testshots/adobecsraw.jpg

The point is that in the future I will trust the histogram more than LCD. I'll say trust you gut feeling and go with it. If you know that metering off grey card should give you neutral grey then lock your exposure off that and shoot away. Your results whould be very close to what you ae looking for. You can then always play around with it later in Photoshop.

Flagpole
Sydney, Australia

[FlyingPete]

Those are some pretty substantial variations!

I have not been shooting much in RAW, due to the extra time required to process the images (in this case over 150 products!), and the actual storage requirements for the RAW image. Do you have a quick batch process you run? I also have Photoshop CS, but haven’t really put much time into the RAW importer.

I work quite carefully to get the images as close to what I want to minimise fussing around afterwards, I guess that is a result of my slide film days, when you only got one shot at it! Old disciplines die hard (should they die at all?)

[Flagpole]

Hey Pete!

Shooting in raw has a number of advantages to me occasionally and with PS CS it is a much better option IMO as it allows you to process large number of raws fairly quickly since you can preset and then load it for each shot as needed or do a batch conversion. The storage for me isn't a problem as CF cards are fairly cheap and if you are planning to do only 150 shots then a 512Mb card should be enough for raw. The good thing about raw is you can sharpen the pictures later and with RAW importer play around to get a more consistent colour. I'll say if you are in doubt with lightning then shoot in raw. If your images are looking the right way without blowing any highlights you can always adjust for colour tint in PS later.

Flagpole

[FlyingPete]

Admittedly, RAW would have got me out of trouble (literally!) a couple of times, when I had set some weird custom white balance, then my wife used the camera only to find they were all pink or blue or yellow!
To this day, I have not been able to correct the pink shots, as for the others I have had limited success.

I will check out the batch function in PS CS, you might be onto something there...