On the second photo, the top half is overexposed, indicating it's too long, resulting in the washeed out white ares. But the bottom is underexposed resulting in blackened lows and lost detail. The cause is not improper exposure, it's uneven lighting, resulting in too much contrast. It's not a bad photo by anymeans, you did the best you could under the conditions. If it were a 1:1 photo, you don't have much control over the conditions. So what can be done? You can try to compensate electronically with some photo software. In 1:1, if you had a 2nd chance, you could return on a cloudy day. On a model, you could provide some auxiliary lighting. I've been using 4 150 watt (I think) halogen work lamps with reasonable results. You can also try to reflect light with a white card, which works pretty well with a digital camera, but takes some real experimnetation with film, unless you have a spot meter.
Whakinacamera?