A little help with exposure

[moizak]

Hi all!

I have recently bought my first 5x4 and I'm relearning my way through analogue photography.

This is a paper negative I exposed today and I have a couple of questions regarding exposure.

http://farm9.staticflickr.com/8072/8438561845_486895a95c_c.jpg (http://www.flickr.com/photos/moiz/8438561845/)
Toy cars - test (http://www.flickr.com/photos/moiz/8438561845/) by Moiz (http://www.flickr.com/people/moiz/), on Flickr

Firstly, do you think it is exposed correctly? Personally, I think it may be a little on the dark side but possibly only half a stop but bear in mind this was a test to see how paper negatives react to colour so the two cars on the right, which were orange and red, were expected to be very dark. The three in the middle are green, blue and purple, from right to left. The digger is yellow and the surface top is a mid blue.

Secondly, I metered this with a Sekonic L-328 incident meter with a dome. The only light source was a large window behind the camera. I metered the scene, valuing the paper at EI3 and got a reading of f13.5 60secs. I set up and shot the image, except my cable release got stuck and I ended up exposing for 80secs.

Then, after I had packed up I realised I had not allowed for bellows extension factor (so much to remember!) which, a rough re-setup revealed to be 1.25stops.

Now I need to calculate what the actual EI of the paper is before doing some more tests and it is making my brain hurt. If we assume that the exposure is correct am I correct in thinking that I should rate the paper at, say, EI5?

Thanks in advance for any replies.

Moiz

PS. the image has had no manipulation other than to be poorly scanned and inverted in PS.

[Pawlowski6132]

Looks underexposed.

[Ken Lee]

For testing purposes we can save a lot of time by choosing a subject with even illumination, neutral colors and a normal level of brightness.

We need the number of variables to be very small: no reciprocity compensation, no bellows compensation, no issues of spectral response.

With a view camera, be sure to use no movements: just shoot through the center of the image circle and place the target in the middle.

Here's a recent film/developer test. Note that the testing information is written on a card and placed in the photo: film, developer, and ISO. (This shows Kodak TMY at ISO 200 developed in Diafine.) Almost all the items are gray, white and black. There is no question about their normal tonal value.

The items in the scene which are black, have texture. The white items have texture also: the white card has some light areas on it where the sunshine has reflected off the large metal object: even that "whiter" white is visible.

http://www.kenleegallery.com/images/forum/diafine200.jpg

[moizak]

Ken, that actually makes perfect sense, thank you. I'll try and find a bunch of neutral coloured items with which to test rather than trying to test multiple things all at once.

[moizak]

http://farm9.staticflickr.com/8244/8456629900_6e7a3a7176_o.png (http://www.flickr.com/photos/moiz/8456629900/)
Kentmere Test 2 (http://www.flickr.com/photos/moiz/8456629900/) by Moiz (http://www.flickr.com/people/moiz/), on Flickr

Right, so my quest to understand paper negatives continues.

I did some tests, as Ken suggested using more neutral objects, and settled on a EI of 6. The test images were very contrasty so it did make it hard to decide on a correct EI but the inclusion of a grey card in the picture helped. I decided it was possible that my developing was not helping matters so I decided to have a look at that.

I set up the scene above, the box is a mid warm grey colour. The day was overcast and in fact started to darken fairly rapidly as rain clouds moved in. I had set up in a conservatory with large clear windows to my left and PVC diffused panels overhead. The light in here is pretty flat with a slight bias toward the windows. The box was placed on a white sheet.

I took a standard incident meter reading, set up the camera and shot 4 images, one after the other, as usual completely forgetting to apply the bellows factor I had so diligently measured (1 stop). After taking the first 2 pictures I took another meter reading as I felt the light level was dropping and found that I needed to open up another half stop. It is possible that the rate at which it was darkening I should have opened up another half stop for the last picture.

Each picture was then developed as shown above. To my amateur eye I can see that the constant agitation was definitely exacerbating the contrast issue and that 2 minutes with no agitation in day old developer left the image underdeveloped.

I think it is going to take further testing to determine whether option 2 or 4 is the way to go. 4 does look darker but that could be under exposure due to the falling light levels.

It is also apparent from the blown out white sheet that keeping the highlights in check is always going to be the biggest challenge. For now I am going to continue to shoot only under overcast conditions and would like to take a similar picture under similar conditions but this time try and nail the exposure. I do feel that this is 1 stop under exposed. After that I may start looking at pre flashing the paper to see how and what that affects.

If you have managed to reach the end of this ramble and feel like adding anything, I'd love to hear it.

Moiz

[pixelda]

If you can borrow a reference card (colour and greyscale), this makes a perfect exposure reference

Meter the white, 18% grey and black and write these down. Expose for the 18% grey and do plus and minus half and one stop to get five test images (even +/- 2 stops, depending on the film)
You can also add some everyday objects into the scene too. Lighting should be consistent for the test. This should show you pretty much what you need to know in terms of exposure and contrast.

I've not performed this for film, but did set up one of my exposure meters for a digital camera using a (proprietry) greysclae card.
In that case, software checks a wide range of expsoures to verify when the lights and darks lose detail and where solid black and white are (this is then shown in the meter display).
If I had the time and money, I could do the same text for film too - although the meter stores only three sets of expsoure range values.

[moizak]

Hi Pixelda

Thanks for the advice. I did do something similar that eventually, setting up a neutral scene and dropping a grey card into it. Paper negs seem to be very fickle though, it's a steep learning curve.