I think that the contrast ratios in your photos are a little too extreme. To get the detail you really need to lower the contrast ratio. I suggest a fill flash or maybe a macro ring flash to assist in doing this.
Secondly, I think that you should stop using a soft focus filter for technical subjects and reserve them for the romantic pictures. In that case, hard light and a softening filter do work well - especially on members of the fairer sex.
Oh. You mean about the spark plugs?
Well, kind of hard to tell because the photos are so bad (see above explanation) but, the ceramic is clean and not cracked, the tips do not appear to be fouled, damaged or melted and they are roughly the right colour.
I'd say that the plugs are healthy. Why? You having problems?
